- Email: [email protected]
Serum zinc levels of cord blood: Relation to birth weight and gestational period
Accepted Manuscript Title: Serum zinc levels of cord blood; relation to birth weight and gestational period Author: Tahiry G´omez Hern´andez Leticia Bequer Mendoza Angel Mollineda Trujillo Olga Lidia Gonz´alez Gonz´alez Mireisy Diaz Hern´andez Douglas Fern´andez Caraballo PII: DOI: Reference:
S0946-672X(14)00260-0 http://dx.doi.org/doi:10.1016/j.jtemb.2014.12.009 JTEMB 25646
To appear in: Received date: Revised date: Accepted date:
21-10-2014 26-12-2014 28-12-2014
Please cite this article as: Hern´andez TG, Mendoza LB, Trujillo AM, Gonz´alez OLG, Hern´andez MD, Caraballo DF, Serum zinc levels of cord blood; relation to birth weight and gestational period, Journal of Trace Elements in Medicine and Biology (2015), http://dx.doi.org/10.1016/j.jtemb.2014.12.009 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Serum zinc levels of cord blood; relation to birth weight and gestational period Short title: Serum zinc levels of cord blood
1 2
Biomedical Research Center, Medical College of Villa Clara, Cuba Las Villas Central University, Cuba
ip t
Tahiry Gómez Hernández1, Leticia Bequer Mendoza1, Angel Mollineda Trujillo2, Olga Lidia González González1, Mireisy Diaz Hernández1, Douglas Fernández Caraballo
an
us
cr
Correspondence to: Tahiry Gomez Hernandez Master in Chemical Science; Biomedical researcher at the Biomedical Research Center, Medical College of Villa Clara, Cuba. e-mail: [email protected] Address: Calle 4ta, No. 323, e/ F y G Rpto. Vigía. Santa Clara. Villa Clara. Cuba. CP: 50200.
M
Leticia Cristina Bequer Mendoza Address: Calle B, No 35 Altos, e/ 2da y 3ra. Rpto. Virginia. Santa Clara, Villa Clara. Cuba. CP: 50100.
d
Angel Mollineda Trujillo Address: Carr. Camajuaní. Km 6,5. CPA Camilo Cienfuegos. Santa Clara, Villa Clara. Cuba.
te
Olga Lidia González González Address: Carr. Maleza Km 91/2, Base Aérea, CPA Frank País. Santa Clara, Villa Clara. Cuba.
Ac ce p
Mireisy Diaz Hernández Address: Calle A, No 91 e/ Danielito y 3ra. Rpto. Virginia. Santa Clara. Villa Clara. Cuba. CP: 50100. Douglas Fernández Caraballo Address: Edificio 109, Apto 9. Calle 6ta y Doble Vía, Apto 9. Rpto. Vigía Sur. Santa Clara. Villa Clara. Cuba. CP: 50200.
Abstract:
Background: Zn-deficiency has been associated with numerous alterations during pregnancy including low birth weight; however, the research relating neonatal zinc status and birth weight has not produced reliable results.
Page 1 of 15
Objective: To compare the serum Zn-levels of cord blood in healthy newborns and low birth weight newborns, and to assess a possible relationship between zinc concentration and neonatal birth weight and gestational age.
ip t
Material and Methods: 123 newborns divided in “study group”(n=50) with <2500g birth weight neonates and “control group”(n=73) with ≥2500g birth weight neonates were enrolled. Study group was subdivided according to gestational age in preterm(<37 weeks)
cr
and full-term(≥37 weeks). Serum cord blood samples were collected and the Zn-levels
us
were analyzed using flame Atomic Absorption Spectrophotometry method and the result was expressed in μmol/L. The Zn-levels were compared between the groups (Mann-
an
Whitney-U test) and the Zn-levels were correlated with the birth weight and gestational age (Spearman’s rank correlations).
Results: Statistically significant low positive correlation between Zn-levels and birth weight
M
(ρ=0.283; p=0.005) was found. No statistically significant difference between Zn-levels of study and control groups [17.00±0.43 Vs. 18.16±0.32(p=0.053)] was found. Statistically
d
significant low positive correlation between Zn-levels and gestational age (ρ=0.351;
te
p=0.001) was found. No statistically significant difference between Zn-levels of preterm as compare to full-term newborns [16.33±0.42 Vs. 18.43±0.93(p=0.079)] was found. Zn-level
Ac ce p
of preterm subgroup was significantly lower compared to control group (p=0.001). Conclusions: Despite low birth weight preterm neonates had significantly lower serum zinc levels of cord blood than healthy term neonates, the correlation between cord blood zinc levels and birth weight and gestational age was lower. The results are not enough to relate the change in cord blood zinc concentration to the birth weight values or gestational period. In relation to complicated pregnancies, further studies regarding zinc levels in blood in our population are required. Key words: birth weight, gestational age, umbilical cord, serum zinc
Page 2 of 15
Serum zinc levels of cord blood; relation to birth weight and gestational period Introduction Low birth weight is a phenomenon that impacts greatly on neonatal and infant mortality in
ip t
children younger than one year (1). Also, children with low birth weight have a
perinatal period, but also childhood and even adulthood (1-4).
cr
considerable morbidity risk; long-term effects of low birth weight affect not only the
us
It has been described that micronutrient deficiencies during pregnancy can cause low birth weight (2). In particular, zinc deficiency has been associated with abnormal conditions pregnancy
including
congenital
malformations
an
during
(anencephaly),
abortions,
intrauterine growth retardation, and prematurity and low birth weight (5-7). Zinc deficiency
M
has a negative effect on the endocrine system, leading to growth failure. Zinc is a key component of the cell architecture and function; it is required for production of several
d
enzymes which are involved in protein synthesis, nucleic acid metabolism and immune
Ac ce p
nucleotides (6).
te
function. In addition it is a structural component of various proteins, hormones and
Low zinc concentrations of low birth weight newborns have been noted in a number of settings in both animal and human populations (6,8,9). In humans, however, the research relating neonatal zinc status and birth weight has not produced consistent results. Many studies establish positive associations between neonatal serum zinc concentration and birth weight (9-11), whereas some studies establish negative associations (12) or did not find significant associations (5,9). Nevertheless, in most of the studies in humans, the alterations have been associated with severe zinc deficiencies (7,13).
Page 3 of 15
The aim of this study was to compare the serum zinc levels of cord blood in healthy newborns and low birth weight newborns, and to assess a possible relationship between zinc concentration and neonatal birth weight and gestational age.
ip t
Methods
This prospective study was conducted at the Biomedical Research Center of Medical
cr
College, in conjunction with the Las Villas Central University and the Obstetric and
us
Gynecological Teaching Hospital in Villa Clara, Cuba. The study protocol and informed consent were approved by the Ethics Committee of the Biomedical Research Center, and
an
the consent was given by the mothers before enrollment.
The study included a total of 123 healthy newborns and low birth weight newborns divided
M
into two groups: a “study group” composed of newborns with birth weight <2500 g, included preterm infants and full-term infants, and a “control group” with healthy infants. All
te
time of delivery.
d
cases were uncomplicated singleton pregnancies and all mothers were 18-34 years at the
Ac ce p
Births with abnormal maternal conditions such as high blood pressure, heart disease, diabetes mellitus, lupus, malignancies, seizure disorders, drug or alcohol abuse, serologic and HIV positive controls, and clinical conditions known to affect mineral metabolism such as severe malnutrition and severe anemia were excluded. Medical and social data on mothers were obtained from available information in their records and after delivery birth weight and sex of the newborn were recorded. Blood was drawn from the umbilical cord immediately after delivery and before separating the cord from the placenta, according to the procedure detailed by our research group (14). After the immediate centrifugation, serum was transferred to deionized tubes, stored and frozen
Page 4 of 15
at –20ºC until determination of zinc concentrations was done. Serum zinc concentration was determined by Atomic Absorption Spectroscopy (AAS) with flame atomization. A Pye Unicam (Cambridge, England) Model SP9 (Philips) Atomic Absorption
ip t
Spectrophotometer, and zinc hollow-cathode lamps as the radiation source was used. Instrumental parameters were adjusted, for example: wavelength: 213.9 nm, flame:
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Air/Acet., band pass: 0.2 nm, lamp current: 5 mA.
us
For calibration, working standard solutions (9.18, 18.36 and 36.72 µmol/L concentrations) were obtained by appropriate dilution of the stock standard solutions of zinc at a
an
concentration of 1000 mg/L (Merck, Darmstadt, Germany). The method of standard addition to a serum pool of cord blood (prepared by our research group) was also used for
M
calibration, according to the method proposed by Ekkehard WR et al. (15).
d
Working standard solutions and samples were dissolved in a non-ionic surfactant solution
te
Triton X-100, 0.003 %, prepared from the commercially available product (BDH Chemicals
Ac ce p
Ltd Poole England). All standards solutions and samples were analyzed in duplicate. All other reagents were of analytical-reagent grade. All solutions were prepared in ultrahigh-quality water. The materials and vessels used for trace analysis were kept in 10% nitric acid for at least 48 h and subsequently washed four times with ultra-high-quality water before use.
Since not all variables showed normal distribution nonparametric tests were applied. Mann Whitney-U test was used to evaluate the difference between the mean zinc concentrations. Spearman’s rank correlation (rho[ρ]) was used to determine relation between serum zinc and birth weight, gestational period, maternal age and maternal weight.
Page 5 of 15
Absolute frequencies and percentages for the analysis of qualitative variables were used. Chi-squared test based on hypotheses of homogeneity was used to determine significant differences with respect to qualitative variables selected.
Ac ce p
te
d
M
an
us
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P values < 0.05 were considered significant.
Page 6 of 15
Results 50 out of 123 neonates were included in the “study group” and the rest (73) were included
ip t
in the “control group”. From all 50 newborns included in the study group, 34 were considered preterm infants (<37 weeks) and the rest (16) were considered full-term (≥37
cr
weeks). The newborns included in the control group were healthy singleton, normal birth weight and full-term newborns. Medical and social data of the study population are shown
us
in Table 1.
an
Figure 1 summarizes serum zinc concentration in umbilical cord according to birth weight and gestational age. Cord blood zinc levels according to birth weight were lower in the
M
study group than in the control group, but there was no statistically significant difference between mean zinc levels (p>0.05). The mean zinc levels according to gestational age into
d
the study group were similar (p>0.05) but, as shown in figure 1, zinc levels in the preterm
te
sub-group were significantly lower (p<0.05) compared to the control group.
Ac ce p
A statistically significant low positive correlation between zinc levels and birth weight and gestational period (ρ=0.283; p=0.005 and ρ=0.351; p=0.001 respectively) was found (figure 2). No correlation between zinc levels and maternal age and maternal weight (ρ=0.129; p=0.160 and ρ=-0.145; p=0.112) was found.
Page 7 of 15
Discussion Births with no risk factors considered as a confounding factor that could affect the birth weight and the levels of zinc were included in this study. Results showed no correlation
ip t
between zinc concentration and maternal age and maternal weight. These results were achieved by rigorous criteria for the inclusion of mothers according to their age and weight
cr
at the beginning of pregnancy. Medical and social details controlled of the study population were in agreement with other similar studies (9,16,17). The researchers in these studies
us
controlled, through criteria, those confounding factors that might affect birth weight and the
an
levels of zinc.
Our research group established the correlation between serum zinc levels and birth weight
M
of newborns. No statistically significant difference between the mean zinc levels in study and control group was found. A statistically significant low positive correlation between
d
cord blood zinc levels and birth weight was also found in this study. Results were similar to
te
previous studies (5,18). The researchers in these studies found no significant relation
Ac ce p
between cord blood zinc levels and low birth weight. To establish the correlation between serum zinc levels and gestational age, our research group worked with two sub-groups of preterm and full-term newborns. No statistically significant difference between the mean zinc levels of preterm as compared to full-term newborns was found. A statistically significant low positive correlation between cord blood zinc levels and gestational age was found in this study. In addition, serum zinc level in cord blood of preterm sub-group was significantly lower compared to control group. These results were in agreement with previous studies which found a similar relation of cord blood zinc levels with birth weight and gestational period (9,10).
Page 8 of 15
These results can be related to the greatest accumulation of zinc, among others considered highly necessary trace element in certain biochemical and physiologic process that take place in the last trimester of the fetus (2,9); it is suggested that absorption of zinc
ip t
increases by an average of 30 % in late pregnancy (13). The neonates with low birth weight are children who are born at the beginning of the third trimester of gestation or
cr
children born as result of complicated pregnancies due to the decrease of the uterine blood flow (2). In both situations, the deposits of nutrients in fetus diminish; therefore,
us
babies born previous to this fetal age should undergo rigorous studies to reveal the levels
an
of these minerals in their organisms in order to receive the necessary contributions immediately to cover the requirements and, also, to fill the deposits (2,9).
M
Serum zinc values obtained in this study were similar to consulted studies (9,19), however these values were relatively higher compared to other papers (5,20,21). Although serum
d
zinc concentration is commonly used as an indicator of zinc status, interpretation of the
te
measurement is difficult because serum zinc concentration decreases with infection, vigorous exercise, and food intake. Assessment is more difficult during pregnancy
(22).
Ac ce p
because serum zinc concentration declines in proportion to the increase in plasma volume
Moreover, it is particularly noteworthy that serum zinc levels of cord blood in this study have been found to be higher than serum zinc levels in adults [15.91 ± 2.42 µmol/L] (23), measured with the same Atomic Absorption Spectrophotometer in the same laboratory. These results are consistent with other studies which have reported high serum zinc levels in cord blood compared with serum zinc levels of mothers and non-pregnant women (21,24), which would support the existence of higher proportion of serum zinc in the newborn; as already mentioned above, a net increase in zinc absorption seems critical in meeting the fetal demands for this mineral (2).
Page 9 of 15
Other results showed that there is no difference between male and female newborns, and serum zinc concentrations in all enrolled newborns were within the normal range established by our research group in umbilical cord serum [11.15 - 24.09 µmol/L] (19).
ip t
The study showed that despite low birth weight preterm neonates had significantly lower serum zinc levels of cord blood than healthy term neonates, the correlation between cord
cr
blood zinc levels and birth weight and gestational age was lower. The results are not
us
enough to relate the change in cord blood zinc concentration to the birth weight values or gestational period. In relation to complicated pregnancies, further studies regarding zinc
an
levels in blood in our population are required.
M
Acknowledgements
We would like to thank the staff of the delivery room at the Obstetric and Gynecological
Ac ce p
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d
Teaching Hospital in Villa Clara, Cuba for the selection and sample collection.
Page 10 of 15
Referencies 1. World Health Organization (WHO). The incidence of low birth weight. A critical review of available information. Journal World Health Statistics Quarterly1980; 33:197-224.
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2. Charlton V. Most important influences on the development and fetal growth. In: Ballard T, editor. Treaty of neonatology. Philadelphia: Saunders, 2010. p. 45-57.
us
Bequer L, Gómez T, Perez-de-Alejo L, Molina O, Peláez MA, Ferrer MT. Biochemical study in cord blood of newborns taking in to account gestational age and birth weight. Revista del Laboratorio Clínico [serial on the Internet]. 2014; DOI: 10.1016/j.labcli.2014.09.002
an
4.
cr
3. Gómez T, Bequer L, Molina O, Alfonso AD, Rodríguez M. Low birth weight: behavior of some associate factors. Revista Latinoamericana de Perinatología 2014; 17(1):30-5.
5. Srivastava S, Mehrotra P, Srivastava SP, Siddiqui M. Some essential elements in maternal and cord blood in relation to birth weight and gestational age of the baby. Biological Trace Element Research 2002; 86(2):97-105.
M
6. Keen CL. Teratogenic effects of essential trace metals: deficiencies and excesses. In: Chang LW, Magos L, Suzuki T, editors. Toxicology of metals. New York: Chemical Rubber Company Press, 1996. p. 977–1001.
te
d
7. Costello A, Osrin D. Micronutrient status during pregnancy and outcomes for newborn infants in developing countries. The Journal of nutrition 2003; 133:1757S1764S.
Ac ce p
8. Golub M, Gershwin M, Hurley L, Baly D, Hendrickx A. Studies of marginal zinc deprivation in rhesus monkeys. II Pregnancy outcome. The American Journal of Clinical Nutrition 1984; 39:879–887. 9. Vinayak M. Comparison of maternal serum and neonatal cord blood levels of zinc in relation to birth weight and period of gestation. Dissertations medical at Rajiv Gandhi University of Health Sciences. 2009. 10. Elizabeth K, Krishnan V. Umbilical cord blood nutrients in low birth weight babies in relation to birth weight and gestational age. Indian Journal of Medical Research 2008; 128:128-33. 11. Jeswani R, Vani S. A study of serum zinc levels in cord blood of neonates and their mothers. Indian Journal Pediatric 1991; 58:683-7. 12. Prema K. Predictive value of serum copper and zinc in normal and abnormal pregnancy. Indian Journal of Medical Research 1980; 71:554-60. 13. King J. Determinants of maternal zinc status during pregnancy. The American Journal of Clinical Nutrition 2000; 71:1334S-43S. 14. Gómez T, Mendoza L, González O. Ethical issues involved in research in cord blood. Revista Hospital Materno Infantil Ramón Sardá 2012; 31(3):137-38.
Page 11 of 15
15. Ekkehlrd WR, Besch OJ. Detection and elimination of contaminations interfering with the determination of zinc in plasma. Clinical Chemistry 1978; 24:675-680. 16. Neggers Y, Cutter G, Acton R, et al. A positive association between maternal serum zinc concentration and birth weight. The American Journal of Clinical Nutrition 1990; 51:678-84.
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17. Tuttle S, Aggett P, Campbell D, Mac Gillivray I. Zinc and copper nutrition in human pregnancy: a longitudinal study in normal primigravidae and in primigravidae at risk of delivering growth retarded baby. The American Journal of Clinical Nutrition 1985; 41:1032-41.
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18. Awadallah S, Abu-Elteen K, Elkarmi A, Qaraein S, Salem M. Maternal and cord blood serum levels of zinc, copper, and iron in healthy pregnant Jordanian women. The Journal of Trace Elements in Experimental Medicine 2004; 17(1):1-8.
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19. Mendoza L,Gómez T, Perez de Alejo L, Mollineda A, Salazar L, Hernández V. Biochemical profile and reference values in umbilical cord blood. Acta Bioquímica Clínica Latinoamericana 2014; 48(3): in press. 20. Cocho A, Alvela M, Alonso J, Fraga J. Study of zinc in serum by the flame injection method in an age group. Química Clínica 1984; 3(4):245-247.
M
21. Baig S, Hasnain N, Ud-din Q. Studies on Zn, Cu, Mg, Ca and Phosphorus in maternal and cord blood. Journal of the Pakistan Medical Association 2003; 53(9).
d
22. Swanson CA, King JC. Reduced serum zinc concentration during pregnancy. Obstetrics and Gynaecology 1983; 62:313-8.
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23. Ballesteros M, Alfonso J, Guirado O, González H, Pérez A, Mollineda A. Serum concentrations of the trace elements iron, copper and zinc in normotensive individuals and hypertensive hyper reactive. Medicentro 2011; 15(2):140-5.
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24. Sultana M, Jahan N, Sultana N, Quraishi S, Chowdhury T. Preterm Delivery: Role of Zinc. Journal of Bangladesh Society of Physiologist 2010; 5(1):27-33.
Page 12 of 15
Table 1: Medical and social details of the study population. Control group (n=73)
Study group (n=50)
P values
Age of mother (years mean±SEM)
26.86±0.61
26.00±0.64
0.984
24.50±0.95
Maternal weight at the a beginning of pregnancy (kg mean±SEM)
57.60±0.60
58.80±0.69
0.216
57.06±1.08
69.9/30.1
72.0/28.0
0.798
87.5/12.5
80.8/19.2
42.0/58.0
0.000*
50.0/50.0
39.26±0.13
35.37±0.41
0.000*
3313±41.89
2033±52.84
50.7/49.3
54.0/46.0
a
Gestational Age (weeks mean±SEM) a
Birth weight (g mean±SEM) Newborn gender (%Female/Male)
b
38.41±0.28
0.000* 2158±55.40 0.718
ip t
0.058
59.62±0.85
0.076
35.3/64.7
0.094
38.2/61.8
0.432
33.94±0.39
0.000*
1974±71.49
0.219
47.1/52.9
0.151
cr
b
Mode of delivery (%Nomal/Cesarian)
P values
26.94±0.79
us
b
Parity (%Primi/Multi)
an
a
Study sub-groups Fullterm Preterm (n=16) (n=34)
68.8/31.3
M
Mother and newborn details
a
te
Data are percentages; *p<0.05 statistically significant difference (Chi-squared test).
Ac ce p
b
d
Data are Mean±Standard Error of Mean (SEM); *p<0.05 statistically significant difference (Mann Whitney-U test).
Page 13 of 15
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Figure 1: Serum Zn levels of cord blood in all groups. Values expressed as Mean±Standard Error of Mean. *p<0.05, statistically significant difference (Mann Whitney-U test).
M an
p=0.053: Significance of Study versus Control groups; p=0.569: Significance of Full-term subgroup versus Control group; *p=0.001: Significance of Preterm subgroup versus
20
*
Ac
Serum-Zn of cord blood (μmol/L)
ce pt
18
ed
Control group; p=0.079: Significance of Preterm versus Full-term subgroups.
16
14 12
10
8
6 4 2 0 Control group Study group
Full term Preterm (Study group) (Study group) Page 14 of 15
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ρ=0.283 p=0.005*
B
ρ=0.351 p=0.001*
Ac
ce pt
ed
A
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Figure 2: Spearman's correlation of serum Zn concentration of cord blood and birth weight (A) and gestational age (B).
Page 15 of 15
S0946-672X(14)00260-0 http://dx.doi.org/doi:10.1016/j.jtemb.2014.12.009 JTEMB 25646
To appear in: Received date: Revised date: Accepted date:
21-10-2014 26-12-2014 28-12-2014
Please cite this article as: Hern´andez TG, Mendoza LB, Trujillo AM, Gonz´alez OLG, Hern´andez MD, Caraballo DF, Serum zinc levels of cord blood; relation to birth weight and gestational period, Journal of Trace Elements in Medicine and Biology (2015), http://dx.doi.org/10.1016/j.jtemb.2014.12.009 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Serum zinc levels of cord blood; relation to birth weight and gestational period Short title: Serum zinc levels of cord blood
1 2
Biomedical Research Center, Medical College of Villa Clara, Cuba Las Villas Central University, Cuba
ip t
Tahiry Gómez Hernández1, Leticia Bequer Mendoza1, Angel Mollineda Trujillo2, Olga Lidia González González1, Mireisy Diaz Hernández1, Douglas Fernández Caraballo
an
us
cr
Correspondence to: Tahiry Gomez Hernandez Master in Chemical Science; Biomedical researcher at the Biomedical Research Center, Medical College of Villa Clara, Cuba. e-mail: [email protected] Address: Calle 4ta, No. 323, e/ F y G Rpto. Vigía. Santa Clara. Villa Clara. Cuba. CP: 50200.
M
Leticia Cristina Bequer Mendoza Address: Calle B, No 35 Altos, e/ 2da y 3ra. Rpto. Virginia. Santa Clara, Villa Clara. Cuba. CP: 50100.
d
Angel Mollineda Trujillo Address: Carr. Camajuaní. Km 6,5. CPA Camilo Cienfuegos. Santa Clara, Villa Clara. Cuba.
te
Olga Lidia González González Address: Carr. Maleza Km 91/2, Base Aérea, CPA Frank País. Santa Clara, Villa Clara. Cuba.
Ac ce p
Mireisy Diaz Hernández Address: Calle A, No 91 e/ Danielito y 3ra. Rpto. Virginia. Santa Clara. Villa Clara. Cuba. CP: 50100. Douglas Fernández Caraballo Address: Edificio 109, Apto 9. Calle 6ta y Doble Vía, Apto 9. Rpto. Vigía Sur. Santa Clara. Villa Clara. Cuba. CP: 50200.
Abstract:
Background: Zn-deficiency has been associated with numerous alterations during pregnancy including low birth weight; however, the research relating neonatal zinc status and birth weight has not produced reliable results.
Page 1 of 15
Objective: To compare the serum Zn-levels of cord blood in healthy newborns and low birth weight newborns, and to assess a possible relationship between zinc concentration and neonatal birth weight and gestational age.
ip t
Material and Methods: 123 newborns divided in “study group”(n=50) with <2500g birth weight neonates and “control group”(n=73) with ≥2500g birth weight neonates were enrolled. Study group was subdivided according to gestational age in preterm(<37 weeks)
cr
and full-term(≥37 weeks). Serum cord blood samples were collected and the Zn-levels
us
were analyzed using flame Atomic Absorption Spectrophotometry method and the result was expressed in μmol/L. The Zn-levels were compared between the groups (Mann-
an
Whitney-U test) and the Zn-levels were correlated with the birth weight and gestational age (Spearman’s rank correlations).
Results: Statistically significant low positive correlation between Zn-levels and birth weight
M
(ρ=0.283; p=0.005) was found. No statistically significant difference between Zn-levels of study and control groups [17.00±0.43 Vs. 18.16±0.32(p=0.053)] was found. Statistically
d
significant low positive correlation between Zn-levels and gestational age (ρ=0.351;
te
p=0.001) was found. No statistically significant difference between Zn-levels of preterm as compare to full-term newborns [16.33±0.42 Vs. 18.43±0.93(p=0.079)] was found. Zn-level
Ac ce p
of preterm subgroup was significantly lower compared to control group (p=0.001). Conclusions: Despite low birth weight preterm neonates had significantly lower serum zinc levels of cord blood than healthy term neonates, the correlation between cord blood zinc levels and birth weight and gestational age was lower. The results are not enough to relate the change in cord blood zinc concentration to the birth weight values or gestational period. In relation to complicated pregnancies, further studies regarding zinc levels in blood in our population are required. Key words: birth weight, gestational age, umbilical cord, serum zinc
Page 2 of 15
Serum zinc levels of cord blood; relation to birth weight and gestational period Introduction Low birth weight is a phenomenon that impacts greatly on neonatal and infant mortality in
ip t
children younger than one year (1). Also, children with low birth weight have a
perinatal period, but also childhood and even adulthood (1-4).
cr
considerable morbidity risk; long-term effects of low birth weight affect not only the
us
It has been described that micronutrient deficiencies during pregnancy can cause low birth weight (2). In particular, zinc deficiency has been associated with abnormal conditions pregnancy
including
congenital
malformations
an
during
(anencephaly),
abortions,
intrauterine growth retardation, and prematurity and low birth weight (5-7). Zinc deficiency
M
has a negative effect on the endocrine system, leading to growth failure. Zinc is a key component of the cell architecture and function; it is required for production of several
d
enzymes which are involved in protein synthesis, nucleic acid metabolism and immune
Ac ce p
nucleotides (6).
te
function. In addition it is a structural component of various proteins, hormones and
Low zinc concentrations of low birth weight newborns have been noted in a number of settings in both animal and human populations (6,8,9). In humans, however, the research relating neonatal zinc status and birth weight has not produced consistent results. Many studies establish positive associations between neonatal serum zinc concentration and birth weight (9-11), whereas some studies establish negative associations (12) or did not find significant associations (5,9). Nevertheless, in most of the studies in humans, the alterations have been associated with severe zinc deficiencies (7,13).
Page 3 of 15
The aim of this study was to compare the serum zinc levels of cord blood in healthy newborns and low birth weight newborns, and to assess a possible relationship between zinc concentration and neonatal birth weight and gestational age.
ip t
Methods
This prospective study was conducted at the Biomedical Research Center of Medical
cr
College, in conjunction with the Las Villas Central University and the Obstetric and
us
Gynecological Teaching Hospital in Villa Clara, Cuba. The study protocol and informed consent were approved by the Ethics Committee of the Biomedical Research Center, and
an
the consent was given by the mothers before enrollment.
The study included a total of 123 healthy newborns and low birth weight newborns divided
M
into two groups: a “study group” composed of newborns with birth weight <2500 g, included preterm infants and full-term infants, and a “control group” with healthy infants. All
te
time of delivery.
d
cases were uncomplicated singleton pregnancies and all mothers were 18-34 years at the
Ac ce p
Births with abnormal maternal conditions such as high blood pressure, heart disease, diabetes mellitus, lupus, malignancies, seizure disorders, drug or alcohol abuse, serologic and HIV positive controls, and clinical conditions known to affect mineral metabolism such as severe malnutrition and severe anemia were excluded. Medical and social data on mothers were obtained from available information in their records and after delivery birth weight and sex of the newborn were recorded. Blood was drawn from the umbilical cord immediately after delivery and before separating the cord from the placenta, according to the procedure detailed by our research group (14). After the immediate centrifugation, serum was transferred to deionized tubes, stored and frozen
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at –20ºC until determination of zinc concentrations was done. Serum zinc concentration was determined by Atomic Absorption Spectroscopy (AAS) with flame atomization. A Pye Unicam (Cambridge, England) Model SP9 (Philips) Atomic Absorption
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Spectrophotometer, and zinc hollow-cathode lamps as the radiation source was used. Instrumental parameters were adjusted, for example: wavelength: 213.9 nm, flame:
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Air/Acet., band pass: 0.2 nm, lamp current: 5 mA.
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For calibration, working standard solutions (9.18, 18.36 and 36.72 µmol/L concentrations) were obtained by appropriate dilution of the stock standard solutions of zinc at a
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concentration of 1000 mg/L (Merck, Darmstadt, Germany). The method of standard addition to a serum pool of cord blood (prepared by our research group) was also used for
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calibration, according to the method proposed by Ekkehard WR et al. (15).
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Working standard solutions and samples were dissolved in a non-ionic surfactant solution
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Triton X-100, 0.003 %, prepared from the commercially available product (BDH Chemicals
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Ltd Poole England). All standards solutions and samples were analyzed in duplicate. All other reagents were of analytical-reagent grade. All solutions were prepared in ultrahigh-quality water. The materials and vessels used for trace analysis were kept in 10% nitric acid for at least 48 h and subsequently washed four times with ultra-high-quality water before use.
Since not all variables showed normal distribution nonparametric tests were applied. Mann Whitney-U test was used to evaluate the difference between the mean zinc concentrations. Spearman’s rank correlation (rho[ρ]) was used to determine relation between serum zinc and birth weight, gestational period, maternal age and maternal weight.
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Absolute frequencies and percentages for the analysis of qualitative variables were used. Chi-squared test based on hypotheses of homogeneity was used to determine significant differences with respect to qualitative variables selected.
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P values < 0.05 were considered significant.
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Results 50 out of 123 neonates were included in the “study group” and the rest (73) were included
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in the “control group”. From all 50 newborns included in the study group, 34 were considered preterm infants (<37 weeks) and the rest (16) were considered full-term (≥37
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weeks). The newborns included in the control group were healthy singleton, normal birth weight and full-term newborns. Medical and social data of the study population are shown
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in Table 1.
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Figure 1 summarizes serum zinc concentration in umbilical cord according to birth weight and gestational age. Cord blood zinc levels according to birth weight were lower in the
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study group than in the control group, but there was no statistically significant difference between mean zinc levels (p>0.05). The mean zinc levels according to gestational age into
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the study group were similar (p>0.05) but, as shown in figure 1, zinc levels in the preterm
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sub-group were significantly lower (p<0.05) compared to the control group.
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A statistically significant low positive correlation between zinc levels and birth weight and gestational period (ρ=0.283; p=0.005 and ρ=0.351; p=0.001 respectively) was found (figure 2). No correlation between zinc levels and maternal age and maternal weight (ρ=0.129; p=0.160 and ρ=-0.145; p=0.112) was found.
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Discussion Births with no risk factors considered as a confounding factor that could affect the birth weight and the levels of zinc were included in this study. Results showed no correlation
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between zinc concentration and maternal age and maternal weight. These results were achieved by rigorous criteria for the inclusion of mothers according to their age and weight
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at the beginning of pregnancy. Medical and social details controlled of the study population were in agreement with other similar studies (9,16,17). The researchers in these studies
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controlled, through criteria, those confounding factors that might affect birth weight and the
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levels of zinc.
Our research group established the correlation between serum zinc levels and birth weight
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of newborns. No statistically significant difference between the mean zinc levels in study and control group was found. A statistically significant low positive correlation between
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cord blood zinc levels and birth weight was also found in this study. Results were similar to
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previous studies (5,18). The researchers in these studies found no significant relation
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between cord blood zinc levels and low birth weight. To establish the correlation between serum zinc levels and gestational age, our research group worked with two sub-groups of preterm and full-term newborns. No statistically significant difference between the mean zinc levels of preterm as compared to full-term newborns was found. A statistically significant low positive correlation between cord blood zinc levels and gestational age was found in this study. In addition, serum zinc level in cord blood of preterm sub-group was significantly lower compared to control group. These results were in agreement with previous studies which found a similar relation of cord blood zinc levels with birth weight and gestational period (9,10).
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These results can be related to the greatest accumulation of zinc, among others considered highly necessary trace element in certain biochemical and physiologic process that take place in the last trimester of the fetus (2,9); it is suggested that absorption of zinc
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increases by an average of 30 % in late pregnancy (13). The neonates with low birth weight are children who are born at the beginning of the third trimester of gestation or
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children born as result of complicated pregnancies due to the decrease of the uterine blood flow (2). In both situations, the deposits of nutrients in fetus diminish; therefore,
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babies born previous to this fetal age should undergo rigorous studies to reveal the levels
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of these minerals in their organisms in order to receive the necessary contributions immediately to cover the requirements and, also, to fill the deposits (2,9).
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Serum zinc values obtained in this study were similar to consulted studies (9,19), however these values were relatively higher compared to other papers (5,20,21). Although serum
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zinc concentration is commonly used as an indicator of zinc status, interpretation of the
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measurement is difficult because serum zinc concentration decreases with infection, vigorous exercise, and food intake. Assessment is more difficult during pregnancy
(22).
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because serum zinc concentration declines in proportion to the increase in plasma volume
Moreover, it is particularly noteworthy that serum zinc levels of cord blood in this study have been found to be higher than serum zinc levels in adults [15.91 ± 2.42 µmol/L] (23), measured with the same Atomic Absorption Spectrophotometer in the same laboratory. These results are consistent with other studies which have reported high serum zinc levels in cord blood compared with serum zinc levels of mothers and non-pregnant women (21,24), which would support the existence of higher proportion of serum zinc in the newborn; as already mentioned above, a net increase in zinc absorption seems critical in meeting the fetal demands for this mineral (2).
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Other results showed that there is no difference between male and female newborns, and serum zinc concentrations in all enrolled newborns were within the normal range established by our research group in umbilical cord serum [11.15 - 24.09 µmol/L] (19).
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The study showed that despite low birth weight preterm neonates had significantly lower serum zinc levels of cord blood than healthy term neonates, the correlation between cord
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blood zinc levels and birth weight and gestational age was lower. The results are not
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enough to relate the change in cord blood zinc concentration to the birth weight values or gestational period. In relation to complicated pregnancies, further studies regarding zinc
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levels in blood in our population are required.
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Acknowledgements
We would like to thank the staff of the delivery room at the Obstetric and Gynecological
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Teaching Hospital in Villa Clara, Cuba for the selection and sample collection.
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Referencies 1. World Health Organization (WHO). The incidence of low birth weight. A critical review of available information. Journal World Health Statistics Quarterly1980; 33:197-224.
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2. Charlton V. Most important influences on the development and fetal growth. In: Ballard T, editor. Treaty of neonatology. Philadelphia: Saunders, 2010. p. 45-57.
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Bequer L, Gómez T, Perez-de-Alejo L, Molina O, Peláez MA, Ferrer MT. Biochemical study in cord blood of newborns taking in to account gestational age and birth weight. Revista del Laboratorio Clínico [serial on the Internet]. 2014; DOI: 10.1016/j.labcli.2014.09.002
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4.
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3. Gómez T, Bequer L, Molina O, Alfonso AD, Rodríguez M. Low birth weight: behavior of some associate factors. Revista Latinoamericana de Perinatología 2014; 17(1):30-5.
5. Srivastava S, Mehrotra P, Srivastava SP, Siddiqui M. Some essential elements in maternal and cord blood in relation to birth weight and gestational age of the baby. Biological Trace Element Research 2002; 86(2):97-105.
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6. Keen CL. Teratogenic effects of essential trace metals: deficiencies and excesses. In: Chang LW, Magos L, Suzuki T, editors. Toxicology of metals. New York: Chemical Rubber Company Press, 1996. p. 977–1001.
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7. Costello A, Osrin D. Micronutrient status during pregnancy and outcomes for newborn infants in developing countries. The Journal of nutrition 2003; 133:1757S1764S.
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8. Golub M, Gershwin M, Hurley L, Baly D, Hendrickx A. Studies of marginal zinc deprivation in rhesus monkeys. II Pregnancy outcome. The American Journal of Clinical Nutrition 1984; 39:879–887. 9. Vinayak M. Comparison of maternal serum and neonatal cord blood levels of zinc in relation to birth weight and period of gestation. Dissertations medical at Rajiv Gandhi University of Health Sciences. 2009. 10. Elizabeth K, Krishnan V. Umbilical cord blood nutrients in low birth weight babies in relation to birth weight and gestational age. Indian Journal of Medical Research 2008; 128:128-33. 11. Jeswani R, Vani S. A study of serum zinc levels in cord blood of neonates and their mothers. Indian Journal Pediatric 1991; 58:683-7. 12. Prema K. Predictive value of serum copper and zinc in normal and abnormal pregnancy. Indian Journal of Medical Research 1980; 71:554-60. 13. King J. Determinants of maternal zinc status during pregnancy. The American Journal of Clinical Nutrition 2000; 71:1334S-43S. 14. Gómez T, Mendoza L, González O. Ethical issues involved in research in cord blood. Revista Hospital Materno Infantil Ramón Sardá 2012; 31(3):137-38.
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15. Ekkehlrd WR, Besch OJ. Detection and elimination of contaminations interfering with the determination of zinc in plasma. Clinical Chemistry 1978; 24:675-680. 16. Neggers Y, Cutter G, Acton R, et al. A positive association between maternal serum zinc concentration and birth weight. The American Journal of Clinical Nutrition 1990; 51:678-84.
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17. Tuttle S, Aggett P, Campbell D, Mac Gillivray I. Zinc and copper nutrition in human pregnancy: a longitudinal study in normal primigravidae and in primigravidae at risk of delivering growth retarded baby. The American Journal of Clinical Nutrition 1985; 41:1032-41.
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18. Awadallah S, Abu-Elteen K, Elkarmi A, Qaraein S, Salem M. Maternal and cord blood serum levels of zinc, copper, and iron in healthy pregnant Jordanian women. The Journal of Trace Elements in Experimental Medicine 2004; 17(1):1-8.
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19. Mendoza L,Gómez T, Perez de Alejo L, Mollineda A, Salazar L, Hernández V. Biochemical profile and reference values in umbilical cord blood. Acta Bioquímica Clínica Latinoamericana 2014; 48(3): in press. 20. Cocho A, Alvela M, Alonso J, Fraga J. Study of zinc in serum by the flame injection method in an age group. Química Clínica 1984; 3(4):245-247.
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21. Baig S, Hasnain N, Ud-din Q. Studies on Zn, Cu, Mg, Ca and Phosphorus in maternal and cord blood. Journal of the Pakistan Medical Association 2003; 53(9).
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22. Swanson CA, King JC. Reduced serum zinc concentration during pregnancy. Obstetrics and Gynaecology 1983; 62:313-8.
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23. Ballesteros M, Alfonso J, Guirado O, González H, Pérez A, Mollineda A. Serum concentrations of the trace elements iron, copper and zinc in normotensive individuals and hypertensive hyper reactive. Medicentro 2011; 15(2):140-5.
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24. Sultana M, Jahan N, Sultana N, Quraishi S, Chowdhury T. Preterm Delivery: Role of Zinc. Journal of Bangladesh Society of Physiologist 2010; 5(1):27-33.
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Table 1: Medical and social details of the study population. Control group (n=73)
Study group (n=50)
P values
Age of mother (years mean±SEM)
26.86±0.61
26.00±0.64
0.984
24.50±0.95
Maternal weight at the a beginning of pregnancy (kg mean±SEM)
57.60±0.60
58.80±0.69
0.216
57.06±1.08
69.9/30.1
72.0/28.0
0.798
87.5/12.5
80.8/19.2
42.0/58.0
0.000*
50.0/50.0
39.26±0.13
35.37±0.41
0.000*
3313±41.89
2033±52.84
50.7/49.3
54.0/46.0
a
Gestational Age (weeks mean±SEM) a
Birth weight (g mean±SEM) Newborn gender (%Female/Male)
b
38.41±0.28
0.000* 2158±55.40 0.718
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0.058
59.62±0.85
0.076
35.3/64.7
0.094
38.2/61.8
0.432
33.94±0.39
0.000*
1974±71.49
0.219
47.1/52.9
0.151
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b
Mode of delivery (%Nomal/Cesarian)
P values
26.94±0.79
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b
Parity (%Primi/Multi)
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a
Study sub-groups Fullterm Preterm (n=16) (n=34)
68.8/31.3
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Mother and newborn details
a
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Data are percentages; *p<0.05 statistically significant difference (Chi-squared test).
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b
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Data are Mean±Standard Error of Mean (SEM); *p<0.05 statistically significant difference (Mann Whitney-U test).
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Figure 1: Serum Zn levels of cord blood in all groups. Values expressed as Mean±Standard Error of Mean. *p<0.05, statistically significant difference (Mann Whitney-U test).
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p=0.053: Significance of Study versus Control groups; p=0.569: Significance of Full-term subgroup versus Control group; *p=0.001: Significance of Preterm subgroup versus
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*
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Serum-Zn of cord blood (μmol/L)
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18
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Control group; p=0.079: Significance of Preterm versus Full-term subgroups.
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14 12
10
8
6 4 2 0 Control group Study group
Full term Preterm (Study group) (Study group) Page 14 of 15
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ρ=0.283 p=0.005*
B
ρ=0.351 p=0.001*
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A
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Figure 2: Spearman's correlation of serum Zn concentration of cord blood and birth weight (A) and gestational age (B).
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