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Longitudinal study of serum minerals, electrolytes, and hemoglobin during second trimester of pregnancy in Pakistani women
Nutridon Research, Vol. 14, No. 7, pp. 977--989, 1994 Copyright 9 1994 Elsevier Science Ltd Printed in the USA. All dgins reserved 0271-5317/94 $6.00 + .00
Pergamon
0271-5317(94)E00028-X
LONGITUDINAL STUDY OF SERUM MINERALS, ELECTROLYTES, AND HEMOGLOBIN DURING SECOND TRIMESTER OF PREGNANCY IN PAKISTANI WOMEN.
Saeed Ahmad Nagra, Ph.D. Biochemistry Section, Institute of Chemistry, University of the Punjab, Lahore 54590, Pakistan.
ABSTRACT
Variations in the serum electrolyte, cadmium, calcium, copper, lead, magnesium, zinc and hemoglobin of urban and rural population were studied during the second trimester of pregnancy. Serum calcium, magnesium and hemoglobin decreased whereas cadmium, copper and potassium increased significantly (P<0.05). Lead, sodium and zinc did not show any variation. The overall mean of serum cadmium, lead and zinc were significantly (P<0.05) higher in urban population as compared with their rural counterparts. For all other serum minerals studied there was a non significant difference between urban and rural groups. Key words: Hemoglobin
Pakistan,
Pregnancy,
Serum
minerals,
INTRODUCTION
The nutritional requirements are increased during pregnancy, however, a number of physiological and cultural adaptations tend to minimize the magnitude of this increase and much of the information relating to foetal nutrition remains too controversial (1). In the later half of the pregnancy a considerable increase in the intake of calcium, iron and other trace minerals is recommended. A
977
978
S.A. NAGRA marked variation in the hematological parameters has been observed during pregnancy which is not comparable with non pregnants (2). In our earlier publications (3-4) we have reported these changes for the first and last trimester of pregnancy. Availability of data on any aspect of pregnancy under local environmental conditions are very limited and more information about the serum mineral responses of pregnancy is required. National Nutrition Survey (5) described a number of differences in the nutritional status of urban and rural population. The objective of the present study is to investigate and compare the variations in the serum concentration of electrolytes, cadmium, calcium, copper, lead, magnesium, zinc and hemoglobin during second trimester of pregnancy in urban and rural population.
METHODS AND MATERIALS
Studv samples Two study groups comprising of 30 women each, about 26-32 years of age belonging to middle income group (6) were selected from:(a) The antenatal clinic of Services Hospital, Lahore. Each women included in the study was questioned whether she consumed any iron/vitamin supplement during pregnancy or not. The information thus obtained revealed that urban women consumed iron and vitamin supplements almost daily (Urban group). The iron was consumed in the form of various hematinic preparations containing 150-200 mg of ferrous sulphate [e.g. Fefol, Feospan, Fefol Vit (SK&F), Fersolate Tab (Glaxo), Sangobion (Merck) etc]. In urban areas women often adhere to the advice of the Physician. It is therefore believed that the information provided by this group pertaining to the consumption of iron/vitamin supplement is correct and true (3). (b) The Basic Health Unit situated at a distance of 20 Km from Lahore in village Maraka. These women revealed on interview that they did not consume any sort of iron/vitamin supplement even on the advice of physician (Rural group). Data Collecti0n The age of pregnancy was recorded by the help of the date of last menstrual cycle and expected date of delivery as recorded in the
MINERALS IN PREGNANCY
979
antenatal history in case of the urban group, whereas for rural one it was confirmed by Lady Health Visitor, after interviewing and examining the women. After the completion of 16,20 and 24 weeks of gestation , 10 ml of fasting venous blood was drawn by disposable syringe, between 8-10 a.m. Blood was allowed to clot for one hour and then centrifuged at 2500 rpm for 15 minutes. Serum thus obtained was refrigerated in evacuated storage tubes free of contaminating effects of laboratory (7). Each sample was processed within 48 hours. Blood samples were also obtained from 30 non pregnant married women each from urban and rural area for the purpose of comparison. Mineral Analysis Mineral analysis was carried out using Varian Atomic Absorption Spectrophotometer model 1275-AA equipped with lamps for different elements. Sample Preparation All the pyrex glassware used in the study was washed and cleaned by the method of Nagra et al (3). All the Chemicals/reagents used were of AnalR grade obtained from Merck/BDH. In 25 ml capacity conical flask 6 ml of serum was mixed with 12 ml of Nitric acid and heated for 30 minutes at 130 ~ on hot plate in a fuming cupboard. When volume was reduced to half (approximately) then added 10 ml of Nitric acid : Perchloric acid (1:1 mixture) and heated to boiling till the contents were clear and volume was reduced to about 3 ml. The digested material was transferred to 10 ml volumetric flask containing 1 ml of 1% lantanum as hydrochloric acid solution of the oxide. The volume was made with doubly distilled demineralized water(8-9). A few blank samples were also prepared by the similar procedure to work out the contribution of the reagents ( if any). Standard curves for different elements were prepared by the method of Nagra et al (3-4). Hemoalobin Hemoglobin was estimated by cyanomethemoglobin (10) using 3317 Merkotest Hemoglobin kit.
method
980
S.A. NAGRA Statistical
Analysis
The comparison between two study groups (i.e. Urban and Rural) and three gestational ages (i.e.16th, 20th and 24th week) was made by using 2-factor analysis of variance for each parameter. The analysis were performed on microcomputer Macintosh Plus using Stat View 512 + software. For multiple comparison of means, data were subjected to the Duncans Multiple Range Test (11).
RESULTS AND DISCUSSION
The results of the study have been summarized in Table 1. Cadmium The urban pregnant women had significantly (P<0.05) higher serum cadmium concentration as compared with their rural counterparts. Towards the end of the second trimester the serum cadmium concentration was significantly elevated. We do not have local study for comparison and we are unable to conclude whether this increase is due to pregnancy or the environmental pollution. Chislom and Handrof (12) has hypothesized that if a women is young, nutritionally deficient in protein and essential minerals, she will absorb substantially more c a d m i u m in late pregnancy. Metallothionein (MT) is a low molecular weight sulphydryl- rich protein believed to function in heavy metal detoxification and in zinc homeostasis (13) . An increased secretion of progesterone from the placenta suppresses the MT activity of heavy metal detoxification and consequently an elevated serum cadmium level in late pregnancy is expected. The apparently higher concentration of cadmium in the serum did not pose any untoward problem for any one included in the study sample. This is in line with the work of Inskip, Beral & McDowall (14) who reported a case study from the Japan that despite a higher cadmium level in plant and soil the human health record was satisfactory and mortality rate over the previous 40 years was below the national average of Japan.
MINERALS IN PREGNANCY
981
TABLE 1 Variations in the concentration of some important serum minerals, electrolytes and hemoglobin during second trimester of pregnancy in Pakistani women (Mean+SD/dl)*. Parameter Study Group
Gestational Age (weeks~ 16th , 20th 24th
Non Pregnant
Calcium (mg)
11.5• 11.0•
10.7• 9.7• 10.2+_3.5b 9.3•
11.2+_2.8 10.8•
Magnesium Urban (mg) Rural
4.2• 4.3•
3.6+_0.5b 3.6• 3.8• 3.5+_0.6b
4.0• 4.2•
Sodium (mg)
343+_36 336+_45
326+_29 349•
340+_41 331•
321• 324•
Potassium Urban (mg) Rural
23.7• 20.8•
25.2• 22.1•
25.8• 24.0•
23.3+_2.9 21.0•
Copper (l~g)
Urban Rural
210+_60a 223• 225• 225•
229• 242•
158+_25 147•
Zinc (l~g)
Urban Rural
140+_36y 117+_47x
Lead (l~g)
Urban Rural
38.3+5.6y 42.7+9.5y 37.3+_6.6y 29+2.3 24.8+_4.1x 28.9+9.3x 27.2+5.5x 19-22
Cadmium (l~g)
Urban Rural
Urban Rural
Urban Rural
Hemoglobin Urban (g) Rural
132+_47y 141 +51 125+_43x 121+_45
22.3+6.5ay 28.6+7.2ay 37.4+6.2by 14.4+5.2ax 13.3+8.5ax 22.8+5.4bx 9.4+1.2a 9.2+1.6a
8.6+1.3b 8.7+1.0b
8.8+1.7b 8.8+1.3b
130+3 5 122+25
27+_2.3 21+1.6 10.6+1.5 10.3+1.9
*Mean+SD in a row followed by different letters (a,b,c) are statistically different at P<0.05, difference between groups is shown by letters x and y.
982
S.A. NAGRA Calcium Statistically non significant difference was observed in the serum calcium status of urban and rural women. A drop in serum calcium level which started at 5th week of gestation (3) progressively increased with gestational age. Despite the variations, serum calcium values at any stage during the second trimester remained within the normal range (15). Pitikin & Gebhardt (16) has reported an identical trend and may be due to enhanced requirements of the growing foetus as calcium is the most important mineral for the development of bones and teeth. The first molar teeth are on their way at the time of birth. However, no change in plasma serum concentration has also been reported till 28th week of gestation (17). These results are suggestive of the possible effect of environment and ecology on the serum calcium status of pregnant women. CODDer Statistical analysis of the data revealed a non significant difference in the serum copper concentration of the urban and rural women. Serum copper concentration was significantly (P<0.05) higher than the first trimester (3) and non pregnants. Serum copper increased linearly with the age of pregnancy (18). Copper being essential nutrient for all the mammals is associated with proteins such as lysyl oxidase (collagen cross linkage), tyrosinase (pigmentation), ceruloplasmin (chief form of plasma copper) and ferroxidase (oxidaton of Fe2+ and Fe3+) (19). Pregnancy is a state of continuous formation of new tissues and bones in the form of growing fetus which result in the elevated concentration of all the aforesaid enzymes and is responsible for higher serum copper during pregnancy. Alternatively, the administration of estrogen has been reported to increase the ceruloplasmin level. An increased secretion of these hormones during pregnancy partially explain for higher serum concentration during pregnancy (20-21)
MINERALS 1N PREGNANCY Lead A significant (P<0.05) difference was observed in the serum lead level of urban and rural population. However, serum lead did not alter significantly with advancing pregnancy. Manser et al (22) has reported a mean serum level for the population of Karachi (Pakistan) as 31.8 l~g/dl of blood for non pregnant women. For the similar population of Lahore, Hussain, Izhar & Khan (23) has reported blood lead concentration as 15.85 I~g/dl. Rahman(24) has reported serum lead concentration of urban non pregnant women in Faisalabad as high as double of their rural counterparts. For a long time blood lead levels not exceeding 40 I~g/dl were considered acceptable. However, 20 I~g/dl has also been recommended as mean acceptable value. FAO/WHO expert committee (25) has recommended 20 ~g/dl as toxic level and blood concentration above 30 I~/dl has been considered suggestive of undue exposure. Whatsoever may be the reference standard, the blood concentration for this heavy metal is higher in the serum of the two groups of t h i s study . A significantly low concentration of serum lead in rural population may be due to a lesser exposure of this group to industrial and traffic emission which is considered major contributory factor to atmospheric lead (25). It is intresting to point out that none of the subjects s h o w e d any apparent complication of lead toxicity. The possible explanation to this phenomenon may be:(i) The half life of lead in blood is 18 hours. It is not good indicator of lead status and reflects only the results of recent exposure to lead (22). (ii) The effect of lead vary from race to race (27) (iii) The presence of a low molecular weight protein has been reported in the RBC of the subjects with high blood lead levels who exhibited no clinical symptom of lead toxicity (28). It was not detected in those with low lead level or in those with high lead level associated clinical symptoms. Possibly this protein is also present in Pakistanis presenting no symptoms of lead toxicity.
983
984
S.A. NAGRA Maane$ivm A non significant difference was observed in the serum magnesium of the two groups studied. At the beginning of the second trimester serum magnesium was slightly higher than values reported for non pregnant women but gradually decreased significantly (P<0.05) with advancing pregnancy. Variations in serum magnesium follow a trend identical to that of calcium. Magnesium is an essential constituent of the bone matrix. Perhaps due to rapid anabolic processes in the development of fetus, its requirements are enhanced. Our results are in line with that of Sheldon et al (29) who studied serial changes in serum magnesium throughout the pregnancy and reported a declining trend in serum magnesium. Zinc Serum zinc was significantly (P<0.05) high in urban women as compared with rural one. The concentration of serum zinc appeared to be stable during second trimester and did show any significant variations with the advancing gestational age. A number of workers has reported a decrease in serum zinc with advancing pregnancy (3033). Our own findings are similar for first and last trimester of pregnancy in Pakistani women (3-4), however we could not find any study specific to second trimester of pregnancy for comparison. Though a decrease in serum zinc in the course of pregnancy is established, It is possible that in the mid of pregnancy it may remain stable for some time. Electrolvtes (Potassium & Sodium~ Statistical analysis of the data pertaining to serum electrolytes of urban and rural population did not reveal any significant difference. Other researchers have reported a significant increase of potassium towards the end of the second trimester (34). Sodium remain almost constant for the two groups studied. These findings agree well with those of Romeo, Alemany and Arola (34) who observed no change in serum sodium in the entire course of pregnancy. However, a decreasing trend in serum electrolytes has also been reported (35-36).
MINERALS IN PREGNANCY Hemoalobin (Hb) Nutritional anaemia has a global particularly common in developing countries women are the most vulnerable group at risk therefore need specific attention of public during pregnancy is associated with foetal (37-38).
prevalence and it is like Pakistan. Pregnant to develop anaemia and health worker. Anaemia morbidity and mortality
There was a non significant difference in Hb values of the two study groups for each month of the second trimester. Rural women had slightly lower Hb values than urban group. Slightly better Hb profile of urban population may be due to continuous consumption of iron/vitamins during the entire period of pregnancy. Either group of women had Hb values much below the minimum standard value of 11 gm/dl suggested by WHO (39). Hb remained constant in case of urban group however it dropped about one per cent in case of rural group and may be attributed to hemodilution and increasing demand of the growing fetus associated with lesser availability of iron/protein. The results of present study are close to those of National Nutrition Survey (5) which indicated an increasing prevalence of anemia according to age i.e. from low of 35 % in mothers aged 15-19 year to a high 66% in mothers over 45 years of age. A comparison of present study with that of Nutrition Survey of West Pakistan (40) do not show much difference in hemoglobin values of women and dimensions of this important public health problem are increasing.
ACKNOWLEDGEMENTS The author would like to thank his graduate students MS Bushra Sultana and Erum Javedan for their assistance in collecting the study samples and help in analytical work.
REFERENCES 1. Giggs CE, Seitchik J. Nutrition in pregnancy. In: Modern nutrition in health and disease. Lea & Febiger, Philadelphia, 1980;745.
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S.A. NAGRA 2. Passmore R, Eastwood MA. Pregnancy, lactation and infancy. In: Human nutrition and dietetics. Churchill Livingstone, Edinburgh, 1987;375. 3. Nagra SA, Jannat A, Farooqi MI, Anwar J. Hemoglobin, serum calcium, copper, magnesium and zinc during the first trimester of pregnancy in Pakistani women. Ecology food Nutr 1989;22:307-312. 4. Nagra SA, Anwar T, Anwar J , Farooqi MI. Longitudinal study in the concentration of serum calcium, copper, magnesium, zinc and hemoglobin during the last trimester of pregnancy in Pakistani women. Nutr Res 1991;11:1341-1348. 5. National Nutrition Survey Report. National Institute of Health, Isiamabad, 1988. 6. Nagra SA, Gilani AH, Ahmad MD, Haq E. A longitudinal study in body weight of Pakistani infants as influenced by socioeconomic status. J Trop Pediatr1984;30:217-221. 7. Clark D, Dagnall RM, West TS. The atomic absorption determination of zinc with graphite furnace. Analytica Chim Acta 1973;63:11-18. 8. Bock R.A Handbook of Decomposition Methods in Analytical Chemistry. International text book Co.London,1979. 9. Welz B. Atomic absorption spectroscopy. Weinheim, VCH Verlagsgesellschaft mbH,1985;277. 10. Hainline A Jr.Hemoglobin. In D.Saligson(Ed) Standard Methods in Clinical Chemistry. Academic Press New York,1958. 11. Snedecor GW and Cochran WG. Statistical Methods. Iowa State University Press,Ames, 1967. 12.Chislom JC, Handroff CR. Zinc, cadmium, metallothionein and progesterone: Do they participate in etiology of pregnancy induced hypertension. Med Hypotheses 1985;17:231-242. 13. Piletz JE, Anderson RD, Berry W. Synthesis and degradation of hepatic metallothionein in mice differing in susceptibility to cadmium toxicity. Biochem Genet 1983;21:561-566.
MINERALS IN PREGNANCY 14. Inskip P, Beral V, McDowall M. Mortality of Shipham residents:40 year follow up. Lancet 1982;1:896-899. 15. Cantarow A, Schepartz B. Biochemistry. Holt Saunders, London, 1980;637-659! 16. Pitikin RM, Gebhardt MP. Serum calcium concentration in human pregnancy. Am J Obstet 1977;127:775-778. 17. Ekeke GI, Nduka N, Rukari A. Serum calcium and protein level in pregnant African Caucasian women. Trop Geograph Med 1987;37:178182. 18. Tuttle S, Aggett PJ, Campbell D, MacGillvary I. Zinc and copper nutrition in human pregnancy: a longitudinal study in normal primigravidae and in primigravidae at risk of delivering a growth retarded baby. Am J Clin Nutr 1985;41:1032-1041. 19. Shearer TR, Lis EW, Johnson KS, Jhonson JR, Prescitt GH. Copper and zinc in the amniotic fluid and serum from high risk pregnant women. Proc Soc Exp Biol Med 1979;161:382-385. 20. Campbell-Brown EP, Ward RJ, Hanies A, North WRS, Abraham RS, Mcfadyan IR, Turnlend Jr, King JC. Zinc and copper in Asian pregnancies. Brit J Obstet Gynaecol 1985;92:875-885. 21. Kundu N, Parke P, Peterson LP, Polmer IS, Olson O. Distribution of serum selenium, copper and zinc in human pregnancy. Arch Environmental Health 1985;40:268-273. 22. Manser WWT, Haider S, Lalani R, Khan MA, Zuberi S.1 Blood lead in Karachi population. Proceeding of the third international congress on trace elements in health and disease. Cukurova University Publishing Company, Adana,1991;247. 23. Hussain T, Khan IUH, Khan MA. Study of the environmental pollutants in and around Lahore city. 1.Determination of lead in blood of various population group. Sci Total Environ 1990;99:134-143. 24. Rahman KU. Comparative hematochemical studies in normal humans and ischemic heart disease patients. M.Phil. Thesis. University of Agriculture, Faisalabad,1992.
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S.A. NAGRA 25. Di-Farranti E. Trace metals: Exposure and health effects. In:Proceedings of the research seminar, university of Surry, Guilford. Oxford:Pergamon Press, 1987. 26. Quinn MJ. Factor affecting blood lead concentration in UK. Results of the EEC blood lead surveys 1979-1981. Int J Epidemol 1985;14:420-431. 27. Royster L, Royster J, Thomson W. Representative hearing levels by race and sex in North Caroline. J Accoust Soc Am 1980;67:551556. 28. Lolin Y, O'Gorman P. An intra erythrocyte lOw molecular weight lead binding protein in acute and chronic lead exposure and its possible protective role in lead toxicity. Ann Clin Biochem 1988;25:688-697. 29. Sheldon Wl, Aspillaga MO, Smith PA, Lind T. The effect of oral iron supplements on zinc and magnesium levels during pregnancy. Brit J Obstet Gynaecol 1985;92:892-898. 30. King JC, Stein T, Doyle M. Effect of vegetarianism on the zinc status of pregnant women. Am J Clin Nutr 1981;34:1049-1055. 31. Breskin MW, Worthington RBS, Knopp RH, Brown Z, Polivie B, Mottet NK, Mills L. First trimester zinc concentration in human pregnancy. Am J Clin Nutr 1983;38:943-953. 32. Hambidge KM, Kreb NF, Jacob MA, Favier A, Guyette L, Ikle DN. Zinc nutritional status during pregnancy. Am J Clin Nutr 1983;37:429-442. 33. Hunt IF, Murphy NJ, Cleaver AE, Faraji B, Swendside ME, Coulson AH, Clark VA, Laine N, Davis CA, Smith JC. Zinc supplementation during pregnancy. Zinc concentration of serum and hair from low income women of Mexican descent. Am J Clin Nutr 1983;37:572-582. 34. Godfery BE, Wadworth GR. Total body potassium in pregnant women. Brit J Obstet Gynecol 1970;77:244-246. 35. Isichi UP, Egwartu WE, Umezeronini EM. Serum and urine electrolytes in primigravidae African during pregnancy and post natal period. Clin Chem Acta 1978;90:115-120.
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989
36. Ekeke GI, Ebirim UA. Serum sodium and potassium in pregnant urban Nigerian and Caucasian women. Trop Geograph Med 1986;38:2832. 37. Bowering J, Lowenberg RL, Morrison MA. Nutritional studies of pregnant women in East Harlem. Am J Clin Nutr 1980;33:1987-96. 38. Garn SM, Keating MT, Falkner F. Hematological pregnancy outcome. Am J Clin Nutr 1981;34;115-117.
status
of
39. Jackson RT, Lathan MC. Anemia in pregnancy in Liberia,West Africa:a theraputic trial. Am J Clin Nutr 1982;35:710-714. 40. Government of Pakistan. Nutrition survey of west Pakistan. Ministry of Health.lslamabad, 1970. Accepted for publication January 4, 1994.
Pergamon
0271-5317(94)E00028-X
LONGITUDINAL STUDY OF SERUM MINERALS, ELECTROLYTES, AND HEMOGLOBIN DURING SECOND TRIMESTER OF PREGNANCY IN PAKISTANI WOMEN.
Saeed Ahmad Nagra, Ph.D. Biochemistry Section, Institute of Chemistry, University of the Punjab, Lahore 54590, Pakistan.
ABSTRACT
Variations in the serum electrolyte, cadmium, calcium, copper, lead, magnesium, zinc and hemoglobin of urban and rural population were studied during the second trimester of pregnancy. Serum calcium, magnesium and hemoglobin decreased whereas cadmium, copper and potassium increased significantly (P<0.05). Lead, sodium and zinc did not show any variation. The overall mean of serum cadmium, lead and zinc were significantly (P<0.05) higher in urban population as compared with their rural counterparts. For all other serum minerals studied there was a non significant difference between urban and rural groups. Key words: Hemoglobin
Pakistan,
Pregnancy,
Serum
minerals,
INTRODUCTION
The nutritional requirements are increased during pregnancy, however, a number of physiological and cultural adaptations tend to minimize the magnitude of this increase and much of the information relating to foetal nutrition remains too controversial (1). In the later half of the pregnancy a considerable increase in the intake of calcium, iron and other trace minerals is recommended. A
977
978
S.A. NAGRA marked variation in the hematological parameters has been observed during pregnancy which is not comparable with non pregnants (2). In our earlier publications (3-4) we have reported these changes for the first and last trimester of pregnancy. Availability of data on any aspect of pregnancy under local environmental conditions are very limited and more information about the serum mineral responses of pregnancy is required. National Nutrition Survey (5) described a number of differences in the nutritional status of urban and rural population. The objective of the present study is to investigate and compare the variations in the serum concentration of electrolytes, cadmium, calcium, copper, lead, magnesium, zinc and hemoglobin during second trimester of pregnancy in urban and rural population.
METHODS AND MATERIALS
Studv samples Two study groups comprising of 30 women each, about 26-32 years of age belonging to middle income group (6) were selected from:(a) The antenatal clinic of Services Hospital, Lahore. Each women included in the study was questioned whether she consumed any iron/vitamin supplement during pregnancy or not. The information thus obtained revealed that urban women consumed iron and vitamin supplements almost daily (Urban group). The iron was consumed in the form of various hematinic preparations containing 150-200 mg of ferrous sulphate [e.g. Fefol, Feospan, Fefol Vit (SK&F), Fersolate Tab (Glaxo), Sangobion (Merck) etc]. In urban areas women often adhere to the advice of the Physician. It is therefore believed that the information provided by this group pertaining to the consumption of iron/vitamin supplement is correct and true (3). (b) The Basic Health Unit situated at a distance of 20 Km from Lahore in village Maraka. These women revealed on interview that they did not consume any sort of iron/vitamin supplement even on the advice of physician (Rural group). Data Collecti0n The age of pregnancy was recorded by the help of the date of last menstrual cycle and expected date of delivery as recorded in the
MINERALS IN PREGNANCY
979
antenatal history in case of the urban group, whereas for rural one it was confirmed by Lady Health Visitor, after interviewing and examining the women. After the completion of 16,20 and 24 weeks of gestation , 10 ml of fasting venous blood was drawn by disposable syringe, between 8-10 a.m. Blood was allowed to clot for one hour and then centrifuged at 2500 rpm for 15 minutes. Serum thus obtained was refrigerated in evacuated storage tubes free of contaminating effects of laboratory (7). Each sample was processed within 48 hours. Blood samples were also obtained from 30 non pregnant married women each from urban and rural area for the purpose of comparison. Mineral Analysis Mineral analysis was carried out using Varian Atomic Absorption Spectrophotometer model 1275-AA equipped with lamps for different elements. Sample Preparation All the pyrex glassware used in the study was washed and cleaned by the method of Nagra et al (3). All the Chemicals/reagents used were of AnalR grade obtained from Merck/BDH. In 25 ml capacity conical flask 6 ml of serum was mixed with 12 ml of Nitric acid and heated for 30 minutes at 130 ~ on hot plate in a fuming cupboard. When volume was reduced to half (approximately) then added 10 ml of Nitric acid : Perchloric acid (1:1 mixture) and heated to boiling till the contents were clear and volume was reduced to about 3 ml. The digested material was transferred to 10 ml volumetric flask containing 1 ml of 1% lantanum as hydrochloric acid solution of the oxide. The volume was made with doubly distilled demineralized water(8-9). A few blank samples were also prepared by the similar procedure to work out the contribution of the reagents ( if any). Standard curves for different elements were prepared by the method of Nagra et al (3-4). Hemoalobin Hemoglobin was estimated by cyanomethemoglobin (10) using 3317 Merkotest Hemoglobin kit.
method
980
S.A. NAGRA Statistical
Analysis
The comparison between two study groups (i.e. Urban and Rural) and three gestational ages (i.e.16th, 20th and 24th week) was made by using 2-factor analysis of variance for each parameter. The analysis were performed on microcomputer Macintosh Plus using Stat View 512 + software. For multiple comparison of means, data were subjected to the Duncans Multiple Range Test (11).
RESULTS AND DISCUSSION
The results of the study have been summarized in Table 1. Cadmium The urban pregnant women had significantly (P<0.05) higher serum cadmium concentration as compared with their rural counterparts. Towards the end of the second trimester the serum cadmium concentration was significantly elevated. We do not have local study for comparison and we are unable to conclude whether this increase is due to pregnancy or the environmental pollution. Chislom and Handrof (12) has hypothesized that if a women is young, nutritionally deficient in protein and essential minerals, she will absorb substantially more c a d m i u m in late pregnancy. Metallothionein (MT) is a low molecular weight sulphydryl- rich protein believed to function in heavy metal detoxification and in zinc homeostasis (13) . An increased secretion of progesterone from the placenta suppresses the MT activity of heavy metal detoxification and consequently an elevated serum cadmium level in late pregnancy is expected. The apparently higher concentration of cadmium in the serum did not pose any untoward problem for any one included in the study sample. This is in line with the work of Inskip, Beral & McDowall (14) who reported a case study from the Japan that despite a higher cadmium level in plant and soil the human health record was satisfactory and mortality rate over the previous 40 years was below the national average of Japan.
MINERALS IN PREGNANCY
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TABLE 1 Variations in the concentration of some important serum minerals, electrolytes and hemoglobin during second trimester of pregnancy in Pakistani women (Mean+SD/dl)*. Parameter Study Group
Gestational Age (weeks~ 16th , 20th 24th
Non Pregnant
Calcium (mg)
11.5• 11.0•
10.7• 9.7• 10.2+_3.5b 9.3•
11.2+_2.8 10.8•
Magnesium Urban (mg) Rural
4.2• 4.3•
3.6+_0.5b 3.6• 3.8• 3.5+_0.6b
4.0• 4.2•
Sodium (mg)
343+_36 336+_45
326+_29 349•
340+_41 331•
321• 324•
Potassium Urban (mg) Rural
23.7• 20.8•
25.2• 22.1•
25.8• 24.0•
23.3+_2.9 21.0•
Copper (l~g)
Urban Rural
210+_60a 223• 225• 225•
229• 242•
158+_25 147•
Zinc (l~g)
Urban Rural
140+_36y 117+_47x
Lead (l~g)
Urban Rural
38.3+5.6y 42.7+9.5y 37.3+_6.6y 29+2.3 24.8+_4.1x 28.9+9.3x 27.2+5.5x 19-22
Cadmium (l~g)
Urban Rural
Urban Rural
Urban Rural
Hemoglobin Urban (g) Rural
132+_47y 141 +51 125+_43x 121+_45
22.3+6.5ay 28.6+7.2ay 37.4+6.2by 14.4+5.2ax 13.3+8.5ax 22.8+5.4bx 9.4+1.2a 9.2+1.6a
8.6+1.3b 8.7+1.0b
8.8+1.7b 8.8+1.3b
130+3 5 122+25
27+_2.3 21+1.6 10.6+1.5 10.3+1.9
*Mean+SD in a row followed by different letters (a,b,c) are statistically different at P<0.05, difference between groups is shown by letters x and y.
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S.A. NAGRA Calcium Statistically non significant difference was observed in the serum calcium status of urban and rural women. A drop in serum calcium level which started at 5th week of gestation (3) progressively increased with gestational age. Despite the variations, serum calcium values at any stage during the second trimester remained within the normal range (15). Pitikin & Gebhardt (16) has reported an identical trend and may be due to enhanced requirements of the growing foetus as calcium is the most important mineral for the development of bones and teeth. The first molar teeth are on their way at the time of birth. However, no change in plasma serum concentration has also been reported till 28th week of gestation (17). These results are suggestive of the possible effect of environment and ecology on the serum calcium status of pregnant women. CODDer Statistical analysis of the data revealed a non significant difference in the serum copper concentration of the urban and rural women. Serum copper concentration was significantly (P<0.05) higher than the first trimester (3) and non pregnants. Serum copper increased linearly with the age of pregnancy (18). Copper being essential nutrient for all the mammals is associated with proteins such as lysyl oxidase (collagen cross linkage), tyrosinase (pigmentation), ceruloplasmin (chief form of plasma copper) and ferroxidase (oxidaton of Fe2+ and Fe3+) (19). Pregnancy is a state of continuous formation of new tissues and bones in the form of growing fetus which result in the elevated concentration of all the aforesaid enzymes and is responsible for higher serum copper during pregnancy. Alternatively, the administration of estrogen has been reported to increase the ceruloplasmin level. An increased secretion of these hormones during pregnancy partially explain for higher serum concentration during pregnancy (20-21)
MINERALS 1N PREGNANCY Lead A significant (P<0.05) difference was observed in the serum lead level of urban and rural population. However, serum lead did not alter significantly with advancing pregnancy. Manser et al (22) has reported a mean serum level for the population of Karachi (Pakistan) as 31.8 l~g/dl of blood for non pregnant women. For the similar population of Lahore, Hussain, Izhar & Khan (23) has reported blood lead concentration as 15.85 I~g/dl. Rahman(24) has reported serum lead concentration of urban non pregnant women in Faisalabad as high as double of their rural counterparts. For a long time blood lead levels not exceeding 40 I~g/dl were considered acceptable. However, 20 I~g/dl has also been recommended as mean acceptable value. FAO/WHO expert committee (25) has recommended 20 ~g/dl as toxic level and blood concentration above 30 I~/dl has been considered suggestive of undue exposure. Whatsoever may be the reference standard, the blood concentration for this heavy metal is higher in the serum of the two groups of t h i s study . A significantly low concentration of serum lead in rural population may be due to a lesser exposure of this group to industrial and traffic emission which is considered major contributory factor to atmospheric lead (25). It is intresting to point out that none of the subjects s h o w e d any apparent complication of lead toxicity. The possible explanation to this phenomenon may be:(i) The half life of lead in blood is 18 hours. It is not good indicator of lead status and reflects only the results of recent exposure to lead (22). (ii) The effect of lead vary from race to race (27) (iii) The presence of a low molecular weight protein has been reported in the RBC of the subjects with high blood lead levels who exhibited no clinical symptom of lead toxicity (28). It was not detected in those with low lead level or in those with high lead level associated clinical symptoms. Possibly this protein is also present in Pakistanis presenting no symptoms of lead toxicity.
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S.A. NAGRA Maane$ivm A non significant difference was observed in the serum magnesium of the two groups studied. At the beginning of the second trimester serum magnesium was slightly higher than values reported for non pregnant women but gradually decreased significantly (P<0.05) with advancing pregnancy. Variations in serum magnesium follow a trend identical to that of calcium. Magnesium is an essential constituent of the bone matrix. Perhaps due to rapid anabolic processes in the development of fetus, its requirements are enhanced. Our results are in line with that of Sheldon et al (29) who studied serial changes in serum magnesium throughout the pregnancy and reported a declining trend in serum magnesium. Zinc Serum zinc was significantly (P<0.05) high in urban women as compared with rural one. The concentration of serum zinc appeared to be stable during second trimester and did show any significant variations with the advancing gestational age. A number of workers has reported a decrease in serum zinc with advancing pregnancy (3033). Our own findings are similar for first and last trimester of pregnancy in Pakistani women (3-4), however we could not find any study specific to second trimester of pregnancy for comparison. Though a decrease in serum zinc in the course of pregnancy is established, It is possible that in the mid of pregnancy it may remain stable for some time. Electrolvtes (Potassium & Sodium~ Statistical analysis of the data pertaining to serum electrolytes of urban and rural population did not reveal any significant difference. Other researchers have reported a significant increase of potassium towards the end of the second trimester (34). Sodium remain almost constant for the two groups studied. These findings agree well with those of Romeo, Alemany and Arola (34) who observed no change in serum sodium in the entire course of pregnancy. However, a decreasing trend in serum electrolytes has also been reported (35-36).
MINERALS IN PREGNANCY Hemoalobin (Hb) Nutritional anaemia has a global particularly common in developing countries women are the most vulnerable group at risk therefore need specific attention of public during pregnancy is associated with foetal (37-38).
prevalence and it is like Pakistan. Pregnant to develop anaemia and health worker. Anaemia morbidity and mortality
There was a non significant difference in Hb values of the two study groups for each month of the second trimester. Rural women had slightly lower Hb values than urban group. Slightly better Hb profile of urban population may be due to continuous consumption of iron/vitamins during the entire period of pregnancy. Either group of women had Hb values much below the minimum standard value of 11 gm/dl suggested by WHO (39). Hb remained constant in case of urban group however it dropped about one per cent in case of rural group and may be attributed to hemodilution and increasing demand of the growing fetus associated with lesser availability of iron/protein. The results of present study are close to those of National Nutrition Survey (5) which indicated an increasing prevalence of anemia according to age i.e. from low of 35 % in mothers aged 15-19 year to a high 66% in mothers over 45 years of age. A comparison of present study with that of Nutrition Survey of West Pakistan (40) do not show much difference in hemoglobin values of women and dimensions of this important public health problem are increasing.
ACKNOWLEDGEMENTS The author would like to thank his graduate students MS Bushra Sultana and Erum Javedan for their assistance in collecting the study samples and help in analytical work.
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S.A. NAGRA 2. Passmore R, Eastwood MA. Pregnancy, lactation and infancy. In: Human nutrition and dietetics. Churchill Livingstone, Edinburgh, 1987;375. 3. Nagra SA, Jannat A, Farooqi MI, Anwar J. Hemoglobin, serum calcium, copper, magnesium and zinc during the first trimester of pregnancy in Pakistani women. Ecology food Nutr 1989;22:307-312. 4. Nagra SA, Anwar T, Anwar J , Farooqi MI. Longitudinal study in the concentration of serum calcium, copper, magnesium, zinc and hemoglobin during the last trimester of pregnancy in Pakistani women. Nutr Res 1991;11:1341-1348. 5. National Nutrition Survey Report. National Institute of Health, Isiamabad, 1988. 6. Nagra SA, Gilani AH, Ahmad MD, Haq E. A longitudinal study in body weight of Pakistani infants as influenced by socioeconomic status. J Trop Pediatr1984;30:217-221. 7. Clark D, Dagnall RM, West TS. The atomic absorption determination of zinc with graphite furnace. Analytica Chim Acta 1973;63:11-18. 8. Bock R.A Handbook of Decomposition Methods in Analytical Chemistry. International text book Co.London,1979. 9. Welz B. Atomic absorption spectroscopy. Weinheim, VCH Verlagsgesellschaft mbH,1985;277. 10. Hainline A Jr.Hemoglobin. In D.Saligson(Ed) Standard Methods in Clinical Chemistry. Academic Press New York,1958. 11. Snedecor GW and Cochran WG. Statistical Methods. Iowa State University Press,Ames, 1967. 12.Chislom JC, Handroff CR. Zinc, cadmium, metallothionein and progesterone: Do they participate in etiology of pregnancy induced hypertension. Med Hypotheses 1985;17:231-242. 13. Piletz JE, Anderson RD, Berry W. Synthesis and degradation of hepatic metallothionein in mice differing in susceptibility to cadmium toxicity. Biochem Genet 1983;21:561-566.
MINERALS IN PREGNANCY 14. Inskip P, Beral V, McDowall M. Mortality of Shipham residents:40 year follow up. Lancet 1982;1:896-899. 15. Cantarow A, Schepartz B. Biochemistry. Holt Saunders, London, 1980;637-659! 16. Pitikin RM, Gebhardt MP. Serum calcium concentration in human pregnancy. Am J Obstet 1977;127:775-778. 17. Ekeke GI, Nduka N, Rukari A. Serum calcium and protein level in pregnant African Caucasian women. Trop Geograph Med 1987;37:178182. 18. Tuttle S, Aggett PJ, Campbell D, MacGillvary I. Zinc and copper nutrition in human pregnancy: a longitudinal study in normal primigravidae and in primigravidae at risk of delivering a growth retarded baby. Am J Clin Nutr 1985;41:1032-1041. 19. Shearer TR, Lis EW, Johnson KS, Jhonson JR, Prescitt GH. Copper and zinc in the amniotic fluid and serum from high risk pregnant women. Proc Soc Exp Biol Med 1979;161:382-385. 20. Campbell-Brown EP, Ward RJ, Hanies A, North WRS, Abraham RS, Mcfadyan IR, Turnlend Jr, King JC. Zinc and copper in Asian pregnancies. Brit J Obstet Gynaecol 1985;92:875-885. 21. Kundu N, Parke P, Peterson LP, Polmer IS, Olson O. Distribution of serum selenium, copper and zinc in human pregnancy. Arch Environmental Health 1985;40:268-273. 22. Manser WWT, Haider S, Lalani R, Khan MA, Zuberi S.1 Blood lead in Karachi population. Proceeding of the third international congress on trace elements in health and disease. Cukurova University Publishing Company, Adana,1991;247. 23. Hussain T, Khan IUH, Khan MA. Study of the environmental pollutants in and around Lahore city. 1.Determination of lead in blood of various population group. Sci Total Environ 1990;99:134-143. 24. Rahman KU. Comparative hematochemical studies in normal humans and ischemic heart disease patients. M.Phil. Thesis. University of Agriculture, Faisalabad,1992.
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S.A. NAGRA 25. Di-Farranti E. Trace metals: Exposure and health effects. In:Proceedings of the research seminar, university of Surry, Guilford. Oxford:Pergamon Press, 1987. 26. Quinn MJ. Factor affecting blood lead concentration in UK. Results of the EEC blood lead surveys 1979-1981. Int J Epidemol 1985;14:420-431. 27. Royster L, Royster J, Thomson W. Representative hearing levels by race and sex in North Caroline. J Accoust Soc Am 1980;67:551556. 28. Lolin Y, O'Gorman P. An intra erythrocyte lOw molecular weight lead binding protein in acute and chronic lead exposure and its possible protective role in lead toxicity. Ann Clin Biochem 1988;25:688-697. 29. Sheldon Wl, Aspillaga MO, Smith PA, Lind T. The effect of oral iron supplements on zinc and magnesium levels during pregnancy. Brit J Obstet Gynaecol 1985;92:892-898. 30. King JC, Stein T, Doyle M. Effect of vegetarianism on the zinc status of pregnant women. Am J Clin Nutr 1981;34:1049-1055. 31. Breskin MW, Worthington RBS, Knopp RH, Brown Z, Polivie B, Mottet NK, Mills L. First trimester zinc concentration in human pregnancy. Am J Clin Nutr 1983;38:943-953. 32. Hambidge KM, Kreb NF, Jacob MA, Favier A, Guyette L, Ikle DN. Zinc nutritional status during pregnancy. Am J Clin Nutr 1983;37:429-442. 33. Hunt IF, Murphy NJ, Cleaver AE, Faraji B, Swendside ME, Coulson AH, Clark VA, Laine N, Davis CA, Smith JC. Zinc supplementation during pregnancy. Zinc concentration of serum and hair from low income women of Mexican descent. Am J Clin Nutr 1983;37:572-582. 34. Godfery BE, Wadworth GR. Total body potassium in pregnant women. Brit J Obstet Gynecol 1970;77:244-246. 35. Isichi UP, Egwartu WE, Umezeronini EM. Serum and urine electrolytes in primigravidae African during pregnancy and post natal period. Clin Chem Acta 1978;90:115-120.
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36. Ekeke GI, Ebirim UA. Serum sodium and potassium in pregnant urban Nigerian and Caucasian women. Trop Geograph Med 1986;38:2832. 37. Bowering J, Lowenberg RL, Morrison MA. Nutritional studies of pregnant women in East Harlem. Am J Clin Nutr 1980;33:1987-96. 38. Garn SM, Keating MT, Falkner F. Hematological pregnancy outcome. Am J Clin Nutr 1981;34;115-117.
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39. Jackson RT, Lathan MC. Anemia in pregnancy in Liberia,West Africa:a theraputic trial. Am J Clin Nutr 1982;35:710-714. 40. Government of Pakistan. Nutrition survey of west Pakistan. Ministry of Health.lslamabad, 1970. Accepted for publication January 4, 1994.