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Weight, Volume and Surface Area of Placenta of Normal Pregnant Women and their Relation to Maternal and Neonatal Parameters in Malay, Chinese and Indian Ethnic Groups
Placenta (2002), 23, 691–696 doi:10.1053/plac.2002.0817, available online at http://www.idealibrary.com on
Weight, Volume and Surface Area of Placenta of Normal Pregnant Women and their Relation to Maternal and Neonatal Parameters in Malay, Chinese and Indian Ethnic Groups S. Sivaraoa, M. K. Vidyadarana,e, A. B. E. Jammalb, S. Zainabc, Y. M. Gohd and K. N. Ramesha a
Department of Biomedical Sciences, b Department of Human Growth and Development, Faculty of Medicine and Health Science, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia, c Department of Obstetrics and Gynaecology, Hospital Kuala Lumpur, d Faculty of Veterinary Science, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia Paper accepted 31 January 2002
This study was conducted to determine the effect of ethnicity on maternal, placental and neonatal parameters. Maternal, placental, and the newborn parameters were corrected for gestational age. The male : female sex ratio was 1 : 1.03. One hundred and forty-four freshly delivered placentae from 55 Malaysian, 51 Chinese, and 38 Indian normal healthy patients were collected and standard stereological methods used to estimate the placental parameters. Pearson’s correlation, Spearman’s correlation and 1-way ANOVA were used to test significance of differences. Placental surface area, placental weight and placental volume of Indians were lower than Malays (P<0.05). Placental weight correlated significantly with neonatal length (r=0.527), birthweight (r=0.665), head circumference (r=0.371) and booking weight (r=0.193) while placental volume correlated with neonatal length (r=0.588), birthweight (r=0.688), head circumference (r=0.384), parity (r=0.202) and booking weight (r=0.219) at P<0.05. Indian babies weight and length were less than Chinese and Malay babies (P<0.05) while booking weight of Indian mothers was less than those of Chinese mothers (P<0.05). Even after being corrected for booking weight, placental parameters of Indian patients were still significantly less than Malays and Chinese (P<0.05). 2002 Published by Elsevier Science Ltd. Placenta (2002), 23, 691–696
INTRODUCTION There has been considerable interest in the study of the human placenta in recent years in order to establish the relationship between placental, maternal and neonatal factors such as birthweight, parity, foetal malnutrition and anaemia (Matheus and Sala, 1989; Anyaegbunam et al., 1994; Honjoh et al., 1994; Blickstein and Ron, 1995; Jackson et al., 1995; Godfrey et al., 1996 and Williams et al., 1997). Studies on placental characteristics such as placental surface area (Cefalo et al., 1977), villous and intervillous space (Mayhew, 1996), diffusing capacity (Reshetnikova et al., 1995), weight and volume can provide valuable information on pregnancy outcome as predictors of future health of the mother and neonate. (Anyaegbunam et al., 1994 and Kaplan, 1996). Many studies have associated placental parameters with neonatal, nutritional, behavioural and environmental factors (Godfrey et al., 1996; Hibbert et al., 1999; Jackson et al., 1995 and Rush et al., 1986). However, there is possibility of their effect being masked or confounded by ethnicity. Previous e
To whom all correspondence should be addressed at: Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor Darul Ehsan, Malaysia. 0143–4004/02/$-see front matter
studies have shown that placental characteristics differ among different ethnic groups (Dombrowski et al., 1994; Perry et al., 1995 and Williams et al., 1997). Dombrowski and colleagues (1994) reported that placental weight was significantly related to ethnicity and stressed that interpretation of indices such as birthweight/length ratios and birthweight/placenta ratios should be specific for ethnicity. Another study by Perry and colleagues (1995) has reported that placental weight of Asian women was lower compared to European and AfroCaribbean women. Thus, it is vital to determine the influence of ethnicity on placental parameters as well as other pregnancy outcomes. Therefore the aim is to study the relationship between maternal size, placental size and foetal size in three ethnic groups namely Malays, Chinese and Indians in our local population.
MATERIALS AND METHODS Population and sample One hundred and forty-nine freshly delivered placentas from normal healthy mothers with singleton pregnancies delivered 2002 Published by Elsevier Science Ltd.
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Placenta (2002), Vol. 23
Table 1. Baseline characteristics of sample of study
Factor Patient age (years) c20 21–25 26–30 31–35 >35 Maternal height (m) c1.40 1.41–1.50 1.51–1.60 1.61–1.70 >1.70 Booking weight (kg) c50 51–60 61–70 71–80 >80 Parity 1 2 3 Gestation age (days) <260 260–269 270–279 280–290 Occupation House wife Clerical work Business work Field work Education level No education Primary Lower secondary Upper secondary Tertiary Total population
M*
C*
I*
Percentage
Cumulative percentage
16 47 46 26 9
5 18 15 11 6
5 13 21 10 2
6 16 10 5 1
11.1 32.6 31.9 18.1 6.3
11.1 43.7 75.6 93.7 100.0
1 24 101 17 1
1 9 40 5 0
0 8 35 7 1
0 7 26 5 0
0.7 16.7 70.1 11.8 0.7
0.7 17.4 87.5 98.6 100.0
13 44 47 35 5
3 20 14 16 2
2 13 21 12 3
8 11 12 7 0
9.0 30.6 32.6 24.3 3.5
9.0 39.6 72.2 96.5 100.0
33 107 4
11 41 3
12 38 1
10 28 0
22.9 74.3 2.8
22.9 97.2 100.0
0 31 70 43
0 11 25 19
0 9 28 14
0 11 17 10
0.0 21.5 48.6 29.9
0.0 21.5 70.1 100.0
97 17 9 21
32 10 4 9
35 6 4 6
30 1 1 6
67.4 11.8 6.3 14.5
67.4 79.2 85.5 100.0
11 35 43 48 7 144
2 4 16 29 4 55
4 17 16 11 3 51
5 14 11 8 0 38
7.6 24.3 29.9 33.3 4.9
7.6 31.9 61.8 95.1 100.0
n
*M=Malays; C=Chinese; I=Indians.
at Hospital Kuala Lumpur (27 000 deliveries per annum) were collected for the study. The placentas were collected from three major ethnic groups namely Malays (55), Chinese (51), and Indians (38). The male : female sex ratio of the newborn was 1 : 1.03. Patients were residents of the Klang Valley and were mostly from middle-income group (based on family income of RM500–1500). Both the husband and wife were from the same ethnic group. Malays are locals and have been residing in the country for many generations (Malays of Indonesian heritage were excluded from the study). Immigrants were excluded from this study. The Indians and Chinese (both husbands and wives) are at least third generation migrants from India and China respectively. The entire study involved healthy mothers without known diseases who were non-anemic, within the normal range of
plasma albumin, and without any complications before and after labour. All patients had spontaneous vaginal births with live-born infants with no detectable congenital malformations at birth. Placentae from mothers who delivered babies by caesarean section or any assisted delivery such as breech or forceps were excluded. Maternal and neonatal data were obtained from the hospital and antenatal records.
Consent and questionnaires Approval from the ethical committee was obtained prior to the commencement of the project. Consent forms and questionnaires were given to both mother and her spouse or witness (if available) at the time of admission to the labour room.
Sivarao et al.: Weight, Volume and Surface Area of Placenta
693
Table 2. Mean and standard error values of placental, maternal and newborn parameters in each ethnic group (adjusted for gestational age). [1-ANOVA was run to compare the means and significant findings were tested with Duncan’s post hoc test] Ethnic Parameters
Malay (57)
Chinese (53)
Indian (39)
P<0.05
Placental surface area (cm2) Placental volume (cm3) Placental weight (g) Birth weight (g) Neonatal length (cm) Head circumference (cm) Booking weight (kg) Patients’ height (m)
308.3a 0.5 438.7a 0.7 447.0a 0.8 3126a 3 48.8a 0.0 33.2a 0.0 64.3ab 0.1 153.9a 0.0
295.3a 0.4 420.9ab 0.7 434.3ab 0.7 3245a 3 49.5b 0.0 33.5a 0.0 65.7a 0.1 155.9a 0.1
267.5b 0.5 389.9b 0.7 399.9b 0.7 2935b 4 48.1c 0.0 33.2a 0.0 60.7b 0.1 154.4a 0.1
* * * * * ns * ns
Note: Mean values with the same superscript within rows are not significantly different from each other at P<0.05. Mean values with different superscripts within rows are significantly differently from each other at P<0.05. *Significant at the 0.05 level. ns, not significant.
Collection and measurement of placental parameters Placentae were collected from patients delivered at 37–42 weeks gestational age. The umbilical cord was clamped at the insertion point immediately after delivery to minimize blood loss from the fetal vasculature. The weight, volume and surface area of placentas were determined after thoroughly wiping the placenta to drain excessive fluid, mucous and maternal blood. The placenta was trimmed after ligating the umbilical cord at approximately 5 mm from the insertion point and removing attached membranes and blood coagula (Mayhew et al., 1984). The trimmed placental weight was determined using an electronic balance while the volume of placenta was estimated by the method of Scherle (1970) which involves submerging the whole placenta in water and weighing the water displaced and converting to cm3. The placental surface area (maternal surface area) in contact with a grid (3030 cm marked in 1 cm increments) was estimated to be the surface area of the placenta.
Data analysis Data were analysed using SPSS for Windows (Version 9.0, SPSS Inc. Chicago, Illinois, USA) using Spearman’s and Pearson’s correlation, regression and 1-way analysis of variance (ANOVA). The placental and neonatal parameters were corrected for gestational age. Placental size (weight, volume and surface area), neonatal size (birthweight, length, head circumference) and maternal parameters (booking weight and height) were tested with 1-way ANOVA for ethnicity effect. Significant findings were followed up with Duncan’s post hoc test.
Pearson’s correlation was used for parametric data (placental, neonatal and maternal parameters) while Spearmen’s correlation was used for non-parametric data (ethnicity).
RESULTS Placental parameters Table 1 shows the baseline characteristics of the patients. Table 2 shows mean values and significance of differences of placental, maternal, and newborn parameters in each ethnic group. The placental surface area of Indians was significantly lower (P<0.05) than the placental surface area of Malays and Chinese. Placental weight and volume of Indians was significantly lower (P<0.05) than that of Malays (Table 2). Placental surface area correlated with birthweight (r=0.577; P<0.05) (Figure 1), neonatal length (r=0.449; P<0.05), head circumference (r=0.267; P<0.05) and parity (r=0.230; P<0.05) [data not shown]. Placental volume correlated with birthweight (r=0.688; P<0.05) (Figure 2), neonatal length (r=0.588; P<0.05), head circumference (r=0.384; P<0.05), parity (r=0.202; P<0.05) and booking weight (r=0.219; P<0.05) [data not shown]. Placental weight correlated with birth weight (r=0.665; P<0.05) (Figure 3), neonatal length (r=0.527; P<0.05), head circumference (r=0.371; P<0.05) and booking weight (r=0.193; P<0.05) [data not shown].
Newborn parameters The weight and length of the Indian babies were significantly (P<0.05) less than Chinese and Malay babies. Chinese babies were shorter than Malay babies but longer than Indian babies (P<0.05). Neonatal weight correlated with booking weight
694
Placenta (2002), Vol. 23 Placental surface area = 14.15 + 0.09* babywtg R2 = 0.37
600.00
Placental surface area = 44.85 + 0.08* babywtg R2 = 0.31
Placental weight = 51.32 + 0.12* babywtg R2 = 0.46
350.00
Placental weight
Placental surface area
400.00
Placental weight = –59.79 + 0.16* babywtg R2 = 0.44
300.00
500.00
400.00
250.00 300.00 Placental weight = –47.47 + 0.15* babywtg R2 = 0.43
Placental surface area = 72.15 + 0.07* babywtg R2 = 0.26
200.00 2000
2500
3000 3500 Neonatal weight
4000
Figure 1. Placental surface area (cm2) plotted against neonatal birthweight (g). Ethnicity of mother ——: Malay; – – –: Chinese; – · – ·: Indian.
2000
2500
3000 3500 Neonatal weight
4000
Figure 3. Placental weight (g) plotted against neonatal birthweight (g). Ethnicity of mother ——: Malay; – – –: Chinese; – · – ·: Indian.
Maternal parameters Placental volume = –50.50 + 0.16* babywtg R2 = 0.49
600.00
Placental volume
Placental volume = 56.46 + 0.11* babywtg R2 = 0.46
500.00
400.00
DISCUSSION
300.00 Placental Volume = –87.17 + 0.16* babywtg R2 = 0.49
2000
The maternal booking weight of Indian mothers was significantly less (P<0.05) than that of Chinese mothers. Booking weight ranged from 44.0–85.0 kg (mean 63.89.7 kg). Patients’ height ranged from 1.40–1.81 m (mean 1.55 0.05 m). Patients’ age, gestational age and parity were not significantly (P<0.05) different among the three ethnic groups. Booking weight correlated with neonatal weight (r=0.34; P<0.05), neonatal length (r=0.297; P<0.05), head circumference (r=0.213; P<0.05), placental weight (r=0.193; P<0.05) and placental volume (r=0.219; P<0.05).
2500
3000 3500 Neonatal weight
4000
Figure 2. Placental volume (cm3) plotted against neonatal birthweight. Ethnicity of mother ——: Malay; – – –: Chinese; – · – ·: Indian.
(r=0.34; P<0.05) and parity (r=0.257; P<0.05). Neonatal length was also significantly (P<0.05) correlated with booking weight (r=0.297; P<0.05), and parity (r=0.262; P<0.05). However, there was no significant (P>0.05) difference among the three ethnic groups for head circumference. The birth weight of Malays ranged from 2240–4130 g (mean 3130398 g), for Chinese 2170–4100 g (mean 3247 368 g) while that of Indians was 2010–4160 g (mean 2947 413 g).
Ethnicity remains one of the common variables studied in evaluating the pregnancy outcome such as birthweight, length, placental weight and volume (Wolfe et al., 1990). Ethnicity has a significant effect on pregnancy outcome such as neonatal birthweight (Gardosi et al., 1992; Grundy and Newman, 1978; McFayden et al., 1984 and Tuck et al., 1983). Of the three ethnic groups, the relationship (regressional analysis) between placental parameters and birthweight of Indians were different compared to the Chinese and Malays. With further analysis, significant differences were also found between booking weight, placental weight and birthweights of each ethnic group. The booking weight of Indian mothers was less than the Chinese mothers but not significantly different than booking weight of Malay mothers. Maniam and colleagues (1996) reported that Indian women were more obese compared to Chinese and Malays in Malaysia. However, the study did not
Sivarao et al.: Weight, Volume and Surface Area of Placenta
take into account socioeconomic status and educational level of the patients. Our study involved mainly middle class patients (family income of RM500–2000) [Mid Term Review of the Seventh Malaysian Plan, 1996–2000] with a primary and secondary level of education. Therefore the results are not exactly comparable. Placental weight and volume were correlated with booking weight of the mother. Placental parameters (weight, volume and surface area), like booking weight were also significantly different between the three ethnic groups. The placental weight of Indian mothers was significantly lower than both Malays and Chinese mothers. Similar observations were also made for placental volume and placental surface area. It is interesting to note that even after being corrected for maternal weight (by dividing by booking weight), these parameters were still found to be significantly lower in Indians compared to Malays and Chinese. This is probably due to several factors including nutrition, socioeconomic status and ethnicity, exercise during pregnancy, stress and paternal factors (Garris et al., 1985; Pathik, 1993; Simpson, 1993 and Bell et al., 1995). However, it appears that ethnicity may be a major factor since even after correcting for booking weight, the placental parameters of Indian were still lower than Chinese and Malays. The pregnant women in this study were
695
classified as a low-risk group by the hospital as they are non-anemic, disease-free, not exposed to alcohol, and both the mother and newborn had no complications before and after delivery. Birthweight and length were also significantly different among different ethnic groups. Indian babies were significantly lighter even after correction for booking weight suggesting that, like placental parameters, birthweight and length may also be influenced by ethnicity. This study had less power to examine the relationship between the maternal, placental and neonatal parameters being limited by estimation of gestational age by menstrual dates (last menstrual period) and involving pregnancies ranging from 37–42 weeks (mean 2750.6 days). Other investigators have used a combination of ultrasound and menstrual dates to estimate gestational age. For example Perry and colleagues (1995) and Williams et al. (1997) used ultrasound and menstrual dates to estimate gestational age throughout pregnancy and therefore have a better chance to detect unrecognized preterm births. Overall, it appears from this study that ethnicity has a confounding effect on maternal, neonatal and placental parameters and so any analysis involving these parameters must take ethnicity into account.
ACKNOWLEDGEMENTS Our sincere gratitude to Prof. Dr E. Malcolm Symonds for his valuable suggestions. The authors would like to thank the Department of O&G, Hospital Kuala Lumpur for permission to conduct the study. Special thanks to Dr Jothimalar Panandam for her assistance on statistical analysis. Also thanks to staff of Anatomy unit, Universiti Putra Malaysia for their cooperation.
REFERENCES Anyaegbunam A, Mikhail M, Axioitis C, Morel MI & Merkatz IR (1994) Placental histology/fetal weight ratios in pregnant women with sickle cell disease: relationship to pregnancy outcome. J Assoc Acad Minor Phys, 5(3), 123–125. Bell RJ, Palma SM & Lumley JM (1995) The effect of vigorous exercise during pregnancy on birth-weight. Aus NZJ Obstet Gynaecol, 35(1), 46–51. Blickstein I & Ron A (1995) Can placental surface area and neonatal weight be predicted from placental surface measurements? Preliminary observations on normal-term pregnancies. Gynecol Obstet Invest, 40(4), 253–256. Cefalo RC, Simkovich JW, Abel F, Hellegers AE & Chez RA (1977) Effect of potential placental surface area reduction on fetal growth. Am J Obstet Gynecol, 129(4), 434–439. Dombrowski MP, Berry SM, Johnson MP, Saleh AA & Sokol RJ (1994) Birth weight-length ratios, ponderal indexes, placental weights, and birthweight-placenta ratios in a large population. Arch Pediatr Adolesc Med, 148(5), 508–512. Gardosi J, Chang A, Kalyan B, Sahota D & Symonds EM (1992) Customised antenatal growth charts. The Lancet, 339, 283–287. Garris DR, Kasperek GJ, Overton SV & Alligood GR (1985) Effects of exercise on fetal-placental growth and uteroplacental blood flow in the rat. Biol Neonat, 47(4), 223–229. Godfrey K, Robinson S, Barker DJP, Osmon C & Cox V (1996) Maternal nutrition in early and late pregnancy in relation to placental and fetal growth. Br Med J, 312, 410. Grundy MFB & Newman GB (1978) Birthweight standards in a community of mixed racil origin. Br J Obstet Gynaecol, 85, 481–486. Hibbert JM, Davidson S, Hall JS & Jackson AA (1999) Maternal pre-pregnancy and placental weight determine birth weight in normal Jamaican infants. West Indian Med J, 48(4), 216–220.
Honjoh Y, Nishimura Y, Kanomata N, Hanioka K, Itoh H & Kubota A (1994) Morphological studies on placenta. Kobe Med J, 40(1), 1–11. Jackson MR, Gott P, Lye SJ, Ritchie JW & Clapp JF 3rd (1995) The effects of maternal aerobic exercise on human placental development: placental volumetric composition and Qsurface areas. Placenta, 16(2), 179–191. Kaplan CG (1996) Postpartum examination of the placenta. Clin Obstet Gynecol, 39(3), 335–548. Maniam T, Rumawas JSP, Schultink WJ & Khor GL (1996) Cardiovascular disease risk factors among Indian subjects living in Kuala Lumpur, MalaysiaAsia. Pacific J Clinical Nutrition, 5(2), 125. Matheus M & Sala MA (1989) Measurement of villus surface area and its regional variation in the human full-term placenta. Gegenbaurs Morphol Jahrb, 135(6), 851–854. Mayhew TM (1996) Patterns of villous and intervillous space growth in human placentas from normal and abnormal pregnancies. Eur J Obstet Gynecol Reprod Biol, 68, 75–82. McFayden IR, Campbell-Brown M, Abraham A, North WRS & Haines AP (1984) Factors affecting birthweights in Hindus, Moslems and Europeans. Br J Obstet Gynaecol, 91, 968–972. Pathik DW (1993) The association between prenatal stress and infant birth weight and gestational age at birth: A prospective investigation. Am J Obstet Gynecol, 169, 858–865. Perry IJ, Beevers DJ, Whincup PH & Bareford D (1995) Predictors of ratio of placental weight to fetal weight in multiethnic community. Br Med J, 310, 436–439. Reshetnikova OS, Burton GJ & Teleshova OV (1994) Placental histomorphometry and morphometric diffusing capacity of the villous membrane in pregnancies complicated Qby maternal iron-deficiency anemia. Am J Obstet Gynecol, 173(3), 724–727.
696 Rush D, Kristal A, Blanc, Navarro C, Chauhan P, Cample BM, Rosso P, Winick M, Brased J & Naeye R (1986) The effect of maternal cigarette smoking on placental Qmorphology, histomorphometry and biochemistry. Am J Perinatol, 3(3), 262–272. Scherle WF (1970) A simple method for volumetry of organ in quantitative stereology. Mickroskopie, 26, 57–60. Simpson JL (1993) Are physical activity and employment related to preterm birth and low birth weight? Am J Obstet Gynecol, 168(1), 1231– 1238.
Placenta (2002), Vol. 23 Tuck SM, Cardozo LD, Studd WW, Gibb DMF & Cooper DJ (1983) Obstetric characteristics in different racial groups. Br J Obstet Gynaecol, 90, 892–897. Williams LA, Evans SF & Newnham JP (1997) Prospective cohort study of factors influencing the relative weights of the placenta and the newborn infant. Br Med J, 314, 1864–1867. Wolfe M, Zador IE, Gross TL, Martier SS & Sokol RJ (1991) The clinical utility of maternal body mass index in pregnancy. Am J Obstet Gynaecol, 164(5), 1306–1310.
Weight, Volume and Surface Area of Placenta of Normal Pregnant Women and their Relation to Maternal and Neonatal Parameters in Malay, Chinese and Indian Ethnic Groups S. Sivaraoa, M. K. Vidyadarana,e, A. B. E. Jammalb, S. Zainabc, Y. M. Gohd and K. N. Ramesha a
Department of Biomedical Sciences, b Department of Human Growth and Development, Faculty of Medicine and Health Science, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia, c Department of Obstetrics and Gynaecology, Hospital Kuala Lumpur, d Faculty of Veterinary Science, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia Paper accepted 31 January 2002
This study was conducted to determine the effect of ethnicity on maternal, placental and neonatal parameters. Maternal, placental, and the newborn parameters were corrected for gestational age. The male : female sex ratio was 1 : 1.03. One hundred and forty-four freshly delivered placentae from 55 Malaysian, 51 Chinese, and 38 Indian normal healthy patients were collected and standard stereological methods used to estimate the placental parameters. Pearson’s correlation, Spearman’s correlation and 1-way ANOVA were used to test significance of differences. Placental surface area, placental weight and placental volume of Indians were lower than Malays (P<0.05). Placental weight correlated significantly with neonatal length (r=0.527), birthweight (r=0.665), head circumference (r=0.371) and booking weight (r=0.193) while placental volume correlated with neonatal length (r=0.588), birthweight (r=0.688), head circumference (r=0.384), parity (r=0.202) and booking weight (r=0.219) at P<0.05. Indian babies weight and length were less than Chinese and Malay babies (P<0.05) while booking weight of Indian mothers was less than those of Chinese mothers (P<0.05). Even after being corrected for booking weight, placental parameters of Indian patients were still significantly less than Malays and Chinese (P<0.05). 2002 Published by Elsevier Science Ltd. Placenta (2002), 23, 691–696
INTRODUCTION There has been considerable interest in the study of the human placenta in recent years in order to establish the relationship between placental, maternal and neonatal factors such as birthweight, parity, foetal malnutrition and anaemia (Matheus and Sala, 1989; Anyaegbunam et al., 1994; Honjoh et al., 1994; Blickstein and Ron, 1995; Jackson et al., 1995; Godfrey et al., 1996 and Williams et al., 1997). Studies on placental characteristics such as placental surface area (Cefalo et al., 1977), villous and intervillous space (Mayhew, 1996), diffusing capacity (Reshetnikova et al., 1995), weight and volume can provide valuable information on pregnancy outcome as predictors of future health of the mother and neonate. (Anyaegbunam et al., 1994 and Kaplan, 1996). Many studies have associated placental parameters with neonatal, nutritional, behavioural and environmental factors (Godfrey et al., 1996; Hibbert et al., 1999; Jackson et al., 1995 and Rush et al., 1986). However, there is possibility of their effect being masked or confounded by ethnicity. Previous e
To whom all correspondence should be addressed at: Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor Darul Ehsan, Malaysia. 0143–4004/02/$-see front matter
studies have shown that placental characteristics differ among different ethnic groups (Dombrowski et al., 1994; Perry et al., 1995 and Williams et al., 1997). Dombrowski and colleagues (1994) reported that placental weight was significantly related to ethnicity and stressed that interpretation of indices such as birthweight/length ratios and birthweight/placenta ratios should be specific for ethnicity. Another study by Perry and colleagues (1995) has reported that placental weight of Asian women was lower compared to European and AfroCaribbean women. Thus, it is vital to determine the influence of ethnicity on placental parameters as well as other pregnancy outcomes. Therefore the aim is to study the relationship between maternal size, placental size and foetal size in three ethnic groups namely Malays, Chinese and Indians in our local population.
MATERIALS AND METHODS Population and sample One hundred and forty-nine freshly delivered placentas from normal healthy mothers with singleton pregnancies delivered 2002 Published by Elsevier Science Ltd.
692
Placenta (2002), Vol. 23
Table 1. Baseline characteristics of sample of study
Factor Patient age (years) c20 21–25 26–30 31–35 >35 Maternal height (m) c1.40 1.41–1.50 1.51–1.60 1.61–1.70 >1.70 Booking weight (kg) c50 51–60 61–70 71–80 >80 Parity 1 2 3 Gestation age (days) <260 260–269 270–279 280–290 Occupation House wife Clerical work Business work Field work Education level No education Primary Lower secondary Upper secondary Tertiary Total population
M*
C*
I*
Percentage
Cumulative percentage
16 47 46 26 9
5 18 15 11 6
5 13 21 10 2
6 16 10 5 1
11.1 32.6 31.9 18.1 6.3
11.1 43.7 75.6 93.7 100.0
1 24 101 17 1
1 9 40 5 0
0 8 35 7 1
0 7 26 5 0
0.7 16.7 70.1 11.8 0.7
0.7 17.4 87.5 98.6 100.0
13 44 47 35 5
3 20 14 16 2
2 13 21 12 3
8 11 12 7 0
9.0 30.6 32.6 24.3 3.5
9.0 39.6 72.2 96.5 100.0
33 107 4
11 41 3
12 38 1
10 28 0
22.9 74.3 2.8
22.9 97.2 100.0
0 31 70 43
0 11 25 19
0 9 28 14
0 11 17 10
0.0 21.5 48.6 29.9
0.0 21.5 70.1 100.0
97 17 9 21
32 10 4 9
35 6 4 6
30 1 1 6
67.4 11.8 6.3 14.5
67.4 79.2 85.5 100.0
11 35 43 48 7 144
2 4 16 29 4 55
4 17 16 11 3 51
5 14 11 8 0 38
7.6 24.3 29.9 33.3 4.9
7.6 31.9 61.8 95.1 100.0
n
*M=Malays; C=Chinese; I=Indians.
at Hospital Kuala Lumpur (27 000 deliveries per annum) were collected for the study. The placentas were collected from three major ethnic groups namely Malays (55), Chinese (51), and Indians (38). The male : female sex ratio of the newborn was 1 : 1.03. Patients were residents of the Klang Valley and were mostly from middle-income group (based on family income of RM500–1500). Both the husband and wife were from the same ethnic group. Malays are locals and have been residing in the country for many generations (Malays of Indonesian heritage were excluded from the study). Immigrants were excluded from this study. The Indians and Chinese (both husbands and wives) are at least third generation migrants from India and China respectively. The entire study involved healthy mothers without known diseases who were non-anemic, within the normal range of
plasma albumin, and without any complications before and after labour. All patients had spontaneous vaginal births with live-born infants with no detectable congenital malformations at birth. Placentae from mothers who delivered babies by caesarean section or any assisted delivery such as breech or forceps were excluded. Maternal and neonatal data were obtained from the hospital and antenatal records.
Consent and questionnaires Approval from the ethical committee was obtained prior to the commencement of the project. Consent forms and questionnaires were given to both mother and her spouse or witness (if available) at the time of admission to the labour room.
Sivarao et al.: Weight, Volume and Surface Area of Placenta
693
Table 2. Mean and standard error values of placental, maternal and newborn parameters in each ethnic group (adjusted for gestational age). [1-ANOVA was run to compare the means and significant findings were tested with Duncan’s post hoc test] Ethnic Parameters
Malay (57)
Chinese (53)
Indian (39)
P<0.05
Placental surface area (cm2) Placental volume (cm3) Placental weight (g) Birth weight (g) Neonatal length (cm) Head circumference (cm) Booking weight (kg) Patients’ height (m)
308.3a 0.5 438.7a 0.7 447.0a 0.8 3126a 3 48.8a 0.0 33.2a 0.0 64.3ab 0.1 153.9a 0.0
295.3a 0.4 420.9ab 0.7 434.3ab 0.7 3245a 3 49.5b 0.0 33.5a 0.0 65.7a 0.1 155.9a 0.1
267.5b 0.5 389.9b 0.7 399.9b 0.7 2935b 4 48.1c 0.0 33.2a 0.0 60.7b 0.1 154.4a 0.1
* * * * * ns * ns
Note: Mean values with the same superscript within rows are not significantly different from each other at P<0.05. Mean values with different superscripts within rows are significantly differently from each other at P<0.05. *Significant at the 0.05 level. ns, not significant.
Collection and measurement of placental parameters Placentae were collected from patients delivered at 37–42 weeks gestational age. The umbilical cord was clamped at the insertion point immediately after delivery to minimize blood loss from the fetal vasculature. The weight, volume and surface area of placentas were determined after thoroughly wiping the placenta to drain excessive fluid, mucous and maternal blood. The placenta was trimmed after ligating the umbilical cord at approximately 5 mm from the insertion point and removing attached membranes and blood coagula (Mayhew et al., 1984). The trimmed placental weight was determined using an electronic balance while the volume of placenta was estimated by the method of Scherle (1970) which involves submerging the whole placenta in water and weighing the water displaced and converting to cm3. The placental surface area (maternal surface area) in contact with a grid (3030 cm marked in 1 cm increments) was estimated to be the surface area of the placenta.
Data analysis Data were analysed using SPSS for Windows (Version 9.0, SPSS Inc. Chicago, Illinois, USA) using Spearman’s and Pearson’s correlation, regression and 1-way analysis of variance (ANOVA). The placental and neonatal parameters were corrected for gestational age. Placental size (weight, volume and surface area), neonatal size (birthweight, length, head circumference) and maternal parameters (booking weight and height) were tested with 1-way ANOVA for ethnicity effect. Significant findings were followed up with Duncan’s post hoc test.
Pearson’s correlation was used for parametric data (placental, neonatal and maternal parameters) while Spearmen’s correlation was used for non-parametric data (ethnicity).
RESULTS Placental parameters Table 1 shows the baseline characteristics of the patients. Table 2 shows mean values and significance of differences of placental, maternal, and newborn parameters in each ethnic group. The placental surface area of Indians was significantly lower (P<0.05) than the placental surface area of Malays and Chinese. Placental weight and volume of Indians was significantly lower (P<0.05) than that of Malays (Table 2). Placental surface area correlated with birthweight (r=0.577; P<0.05) (Figure 1), neonatal length (r=0.449; P<0.05), head circumference (r=0.267; P<0.05) and parity (r=0.230; P<0.05) [data not shown]. Placental volume correlated with birthweight (r=0.688; P<0.05) (Figure 2), neonatal length (r=0.588; P<0.05), head circumference (r=0.384; P<0.05), parity (r=0.202; P<0.05) and booking weight (r=0.219; P<0.05) [data not shown]. Placental weight correlated with birth weight (r=0.665; P<0.05) (Figure 3), neonatal length (r=0.527; P<0.05), head circumference (r=0.371; P<0.05) and booking weight (r=0.193; P<0.05) [data not shown].
Newborn parameters The weight and length of the Indian babies were significantly (P<0.05) less than Chinese and Malay babies. Chinese babies were shorter than Malay babies but longer than Indian babies (P<0.05). Neonatal weight correlated with booking weight
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Placenta (2002), Vol. 23 Placental surface area = 14.15 + 0.09* babywtg R2 = 0.37
600.00
Placental surface area = 44.85 + 0.08* babywtg R2 = 0.31
Placental weight = 51.32 + 0.12* babywtg R2 = 0.46
350.00
Placental weight
Placental surface area
400.00
Placental weight = –59.79 + 0.16* babywtg R2 = 0.44
300.00
500.00
400.00
250.00 300.00 Placental weight = –47.47 + 0.15* babywtg R2 = 0.43
Placental surface area = 72.15 + 0.07* babywtg R2 = 0.26
200.00 2000
2500
3000 3500 Neonatal weight
4000
Figure 1. Placental surface area (cm2) plotted against neonatal birthweight (g). Ethnicity of mother ——: Malay; – – –: Chinese; – · – ·: Indian.
2000
2500
3000 3500 Neonatal weight
4000
Figure 3. Placental weight (g) plotted against neonatal birthweight (g). Ethnicity of mother ——: Malay; – – –: Chinese; – · – ·: Indian.
Maternal parameters Placental volume = –50.50 + 0.16* babywtg R2 = 0.49
600.00
Placental volume
Placental volume = 56.46 + 0.11* babywtg R2 = 0.46
500.00
400.00
DISCUSSION
300.00 Placental Volume = –87.17 + 0.16* babywtg R2 = 0.49
2000
The maternal booking weight of Indian mothers was significantly less (P<0.05) than that of Chinese mothers. Booking weight ranged from 44.0–85.0 kg (mean 63.89.7 kg). Patients’ height ranged from 1.40–1.81 m (mean 1.55 0.05 m). Patients’ age, gestational age and parity were not significantly (P<0.05) different among the three ethnic groups. Booking weight correlated with neonatal weight (r=0.34; P<0.05), neonatal length (r=0.297; P<0.05), head circumference (r=0.213; P<0.05), placental weight (r=0.193; P<0.05) and placental volume (r=0.219; P<0.05).
2500
3000 3500 Neonatal weight
4000
Figure 2. Placental volume (cm3) plotted against neonatal birthweight. Ethnicity of mother ——: Malay; – – –: Chinese; – · – ·: Indian.
(r=0.34; P<0.05) and parity (r=0.257; P<0.05). Neonatal length was also significantly (P<0.05) correlated with booking weight (r=0.297; P<0.05), and parity (r=0.262; P<0.05). However, there was no significant (P>0.05) difference among the three ethnic groups for head circumference. The birth weight of Malays ranged from 2240–4130 g (mean 3130398 g), for Chinese 2170–4100 g (mean 3247 368 g) while that of Indians was 2010–4160 g (mean 2947 413 g).
Ethnicity remains one of the common variables studied in evaluating the pregnancy outcome such as birthweight, length, placental weight and volume (Wolfe et al., 1990). Ethnicity has a significant effect on pregnancy outcome such as neonatal birthweight (Gardosi et al., 1992; Grundy and Newman, 1978; McFayden et al., 1984 and Tuck et al., 1983). Of the three ethnic groups, the relationship (regressional analysis) between placental parameters and birthweight of Indians were different compared to the Chinese and Malays. With further analysis, significant differences were also found between booking weight, placental weight and birthweights of each ethnic group. The booking weight of Indian mothers was less than the Chinese mothers but not significantly different than booking weight of Malay mothers. Maniam and colleagues (1996) reported that Indian women were more obese compared to Chinese and Malays in Malaysia. However, the study did not
Sivarao et al.: Weight, Volume and Surface Area of Placenta
take into account socioeconomic status and educational level of the patients. Our study involved mainly middle class patients (family income of RM500–2000) [Mid Term Review of the Seventh Malaysian Plan, 1996–2000] with a primary and secondary level of education. Therefore the results are not exactly comparable. Placental weight and volume were correlated with booking weight of the mother. Placental parameters (weight, volume and surface area), like booking weight were also significantly different between the three ethnic groups. The placental weight of Indian mothers was significantly lower than both Malays and Chinese mothers. Similar observations were also made for placental volume and placental surface area. It is interesting to note that even after being corrected for maternal weight (by dividing by booking weight), these parameters were still found to be significantly lower in Indians compared to Malays and Chinese. This is probably due to several factors including nutrition, socioeconomic status and ethnicity, exercise during pregnancy, stress and paternal factors (Garris et al., 1985; Pathik, 1993; Simpson, 1993 and Bell et al., 1995). However, it appears that ethnicity may be a major factor since even after correcting for booking weight, the placental parameters of Indian were still lower than Chinese and Malays. The pregnant women in this study were
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classified as a low-risk group by the hospital as they are non-anemic, disease-free, not exposed to alcohol, and both the mother and newborn had no complications before and after delivery. Birthweight and length were also significantly different among different ethnic groups. Indian babies were significantly lighter even after correction for booking weight suggesting that, like placental parameters, birthweight and length may also be influenced by ethnicity. This study had less power to examine the relationship between the maternal, placental and neonatal parameters being limited by estimation of gestational age by menstrual dates (last menstrual period) and involving pregnancies ranging from 37–42 weeks (mean 2750.6 days). Other investigators have used a combination of ultrasound and menstrual dates to estimate gestational age. For example Perry and colleagues (1995) and Williams et al. (1997) used ultrasound and menstrual dates to estimate gestational age throughout pregnancy and therefore have a better chance to detect unrecognized preterm births. Overall, it appears from this study that ethnicity has a confounding effect on maternal, neonatal and placental parameters and so any analysis involving these parameters must take ethnicity into account.
ACKNOWLEDGEMENTS Our sincere gratitude to Prof. Dr E. Malcolm Symonds for his valuable suggestions. The authors would like to thank the Department of O&G, Hospital Kuala Lumpur for permission to conduct the study. Special thanks to Dr Jothimalar Panandam for her assistance on statistical analysis. Also thanks to staff of Anatomy unit, Universiti Putra Malaysia for their cooperation.
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