July 1991, Volume 41, Issue 7

Original Article

MATERNAL FACTORS AFFECTING BIRTH WEIGHT OF UNCOMPLICATED PREGNANCY

Talat J. Hassan  ( Pakistan Medical Research Council, Research Centre, Jinnah Postgraduate Medical Centre, Karachi. )
Khushnaseeb Ibrahim  ( Pakistan Medical Research Council, Research Centre, Jinnah Postgraduate Medical Centre, Karachi. )
Masoodul Haque  ( Statistic Department, Karachi University, Karachi. )
Sadiqua Naeem Jafarey  ( Department of Obstetric & Gynaecology, Jinnah Postgraduate Medical Centre, Karachi. )
S. Ejaz Alam  ( Pakistan Medical Research Council, Research Centre, Jinnah Postgraduate Medical Centre, Karachi. )

ABSTRACT

Two hundred full-term pregnant mothers with no complication of pregnancy and no associated disease selected from Jinnah Postgraduate Medical Centre were studied for their nutritional status and other characteristics. The effect of these factors on birthweight of their new-born was determined. Total calorie intake per capita per day was low being 1913. The mean birthweight was 2.9kg, 26% weighed 2.5kg or less. No significant sex difference was observed in the birthweight. Variables having a significant positive influence on birthweight were maternal age at first delivery, upto 25 years, beyond which correlation was not significant; maternal weight and maternal total calorie intake (irrespective of source) upto an intake of 2500 calorie per day, beyond which correlation was not significant. Combined effect of these three maternal factors on birthweight was highly significant. Coefficient of correlation, A being 0.81 (JPMA 41: 164, 1991).

INTRODUCTION

Birthweight is a possible crucial factor in perinatal mortality and retarded child development, both physical and mental1-3. Variation in birthweight occurs in last trimester and is influenced to a great extent by factors in the maternal environment. This cross-sectional study was designed to identify these various etiological factors responsible for low birthweight deliveries in our sub­jects.

SUBJECTS AND METHODS

Karachi is a cosmopolitan city inhabited by different ethnic groups. Jinnah Postgraduate Medical Centre UPMC) is one of the largest general hospitals (1000 beds) of this city and gives medical coverage to a large fraction of the population especially of middle and low income groups. This study fairly represents the Karachi popula­tion and comprises subjects of middle and low income groups. Full term pregnant mothers with a single foetus and no complication of pregnancy (normal pregnant mothers) were included in this study. If any complication arose during pregnancy, case was excluded. A total of 200 normal pregnant mothers were selected from obstetric department JPMC. The following information was ob­tained from each subject and recorded on a special proforma-age, age at marriage, age at first delivery, parity, occupation, husband’s occupation, total monthly in­come, total family members, total number of earning family members (from the last three information income per person per day was calculated) number of working hours, type of work and number of helping hands at work. Nutritional status was determined clinically by the technique of Jeliffe4 and by dietary intake. Maternal anthropometric measurement (taken between 1-6 days before delivery) included height, weight, mid-upper arm circumference and triceps skin-fold thickness (Table-I).

Anth­ropometric meas­urements of new-born taken within first 24 hours of delivery included in addition to the above measurements, chest and head circumference (Table II).


Mothers
The weight was taken in kilogram nearest to 0.1kg by spring scale which was checked for zero error before weighing each subject. The height was recorded in cms nearest to 0.1cm by scale fixed to a wall. Subject was bare foot, standing on a flat floor by the scale with feet parallel and with heels, buttocks, shoulders and back of the head touching upright, the arms hanging at the side in a natural manner. The head piece which was a wooden block, was lowered gently, depressing the hair and making contact with the top of the head. The mid-upper arm circumference was measured to the nearest 0.1cm with a tape. The arm was hanging freely by the side and measurement was taken halfway between tip of the acromion process of scapula and the olcrenon process of the ulna. Tricep skin fold thickness was measured nearest to 0.1cm by the Harpenden caliper. The skin fold parallel to the long axis was picked up at mid point, selected as described before, between the thumb and fore finger of the left hand, clean away from the under lying muscle and measured.
Newborn
Weight was taken by beam balance scale, which was corrected for zero error each time before weighing. The weight was taken nearest to 0. 1kg with no clothes on the baby. The height (crown heel length) was measured nearest to 0.1cm by a tape by holding the new born with the feet, so that fiexion at lower extremities was undone and measurement was taken between heel and crown. Head circumference was taken (nearest to 0.1cm) by placing the tape firmly around the frontal bones just superior to the supraoibital ridges passing it round the head at the same level on each side, and laying it over the maximum occipital prominences at the back (oc­cipitofrontal diameter). The chest circumference was measured at nipple line by a tape nearest to 0.1cm. The mid upper arm circumference and triceps skin fold TABLEIII. Foal in take of 200 pregnant women thickness were measured as described for mothers. Dietary history was taken by one week recall method in a single sitting and intake recorded as food intake per capita per day from food composition tables5 (Table III).


Statistical analysis
The effect of maternal height, weight, age at first delivery, total calorie intake and protein intake on birthweight was studied by unvariate analysis. The combined effect of these variables on birthweight was further examined by multiple regression analysis6.

RESULTS

Ml the subjects were from middle and low socioeconomic group. Income per person per day was Rs. 8.90. Family size ranged between 2-13, mean 7. Mean parity was 3.7 (range 0-10), period of gestation was between 37-40 weeks (mean 38 weeks). The average age of mothers at the time of registra­tion was 26.6 years (range 16-45) age at marriage 18.5 years (range 12-34 years) and age at first delivery was 19.6 years (range 14-32 years). Clinical anaemia was present in 64%. Anthropometric measurements (Table I) were below the Harvard standard7.
Dietary assessment
Dietary history revealed that over 70% of mothers took no fish, no eggs and vitamins supplement was minimal. Total caloric intake was mostly from car­bohydrate, protein intake was minimal.
Nutrient intake
From the daily/capita consumption of food mean calorie, protein, fat, minerals and vitamin were calculated (Table IV).

Compared to recommended daily intake assigned by Pakistan Planning Division 1980 (Table IV), the diet was low in calorie, protein, vitamin A, riboflavin and niacin and deficient in animal protein, calcium and iron. Vitamin C intake was good.
Newborn
Anthropometric measurement (Table II) showed mean weight as 2.9kg and 26% of the newborn were <2.5kg (Table V).


Multiple regression analysis
The combined effect of maternal weight, maternal age at first delivery and total calorie intake on birthweight as examined by Multiple Regression analysis was highly significant (P <0.01). The value of R coefficient of multiple correlation, being 0.81, which is quite a high value of correlation.

DISCUSSION

Mean birthweight of singleton normal pregnancies in this study is 2.9kg. The weight distribution showed that 26% of the newborn were low birthweight, weighing <2.5kg which is less than 33.3% reported from South India8 and 29.9% reported by Bhatia et al9, but is very high as compared with the developed countries10. A compara­tively lower incidence (21.3%) was also reported from Nigeria11,12, but these studies included multiple pregnan­cies, prematurity, preeclampsia, whereas the present study included singleton uncomplicated pregnancies delivering at term. Of the various factors responsible for low birth weight (LBW) in our subjects malnutrition is perhaps the most contentious which is in line with the findings of other workers in this field2,3,5,13-20. According to Birmingham study14 on Asian and European mothers, if Asian mothers have a high nutritional status in the second trimester of pregnancy, they can achieve their full genetic potential for intra-uterine growth, that is a rate comparable to the Europeans. Nutritional status of mothers in this study is far from satisfactory as evident by anthropometric measurements (Table I) and dietary intake (Table III). The combined effect of maternal total calorie intake, maternal weight and maternal age at first delivery on the birth weight of babies as examined by multiple regression analysis was highly significant. Correlation between maternal total calorie intake and birth weight was significant only upto a total calorie intake of 2,500 cal/day beyond which the significance did not exist. Same is the case with maternal weight and birth weight, the correlation significance disappearing after a certain point of mother’s weight. Probably the effect of increased calorie intake by mother improves birth weight if mother is under-nourished, but once the requirement of pregnancy is fulfilled, increase in calorie intake may improve mother’s weight alone but had no effect on baby’s weight. This threshold effect of calorie intake, also reported by other workers16-18 may be the reason for conflicting results in various studies15,19. According to this study, as also reported in the past21-23, maternal weight appears to have a positive influence on birth weight. The correlation between maternal age at first delivery and birth weight both in primiparas and multi­paras observed in this study is in agreement with the reported correlation12,24-30. Van den Berg24, observed that teenage mothers are more likely to have low birth weight infants than the older mothers, and that sub­sequent infants born to women who started child-bearing at an early age had an increased incidence of low birth weight. Positive effect of maternal age on birth weight was not significant after age 25 years, among our subjects. A similar effect of maternal age on birth weight was also seen among house mothers12 and in few other studies25-26. It has been postulated that among rapidly growing teenagers nutritional requirements of pregnancy may be greater than those of older women and this increased requirement competes with the growth needs of the foetus30. Some workers do not consider age as an important variabl23,31. The effect of parity on birth weight is not well established. Some studies have shown an influence12,22,24,26 while others, like the present study were not able to establish it32. Certain cross sectional studies have shown au-shaped dependence on parity in which second and third pregnancies are the safest21. Short interval between pregnancies and hard physical work during pregnancy may also be responsible for our low birth weight babies21,33-37. No sex difference was observed in the birth weight in this study. Possible explanation is that our subjects were under-nourished and intrauterine growth which is faster in male foetus during the last trimester of pregnan­cy was affected38. The finding is supported by the fact that various supplementation studies29,33 and studies on well nourished mothers show a sex differentiation in birth weight but not the studies on under-nourished mothers17,20. Various factors adversely affecting birth weight, seen in present study are preventable and it is therefore possible to reduce the frequency of low birth weight babies among our subjects.

REFERENCES

1. Beydoun, S. N., Guenga, V. G., Evans, L. P. and aubry, 8. H. Maternal nutrition. I. The  urInary urea nitrogen/total nitrogen ratio as an index of protein nutrition. Am. J. Obstet.  Gynecot., 1972; 114; 198.
2. Bergner, L. and Susser, M. W. Low birth weight and prenatal nutrition: An interpretative  review. Pediatrics, 1970; 46: 1946.
3. Naismith, D.J. Symposium on numnon of the mothers and child. Maternal nutrition and the  outcome of pregnancy- a critical appraisal. Proc. Nuir. Soc., 1980; 39; 1.
4. Jellife, D. B. The assessment of nutritional status of the community, Geneva, WHO  MonographSeries No. 53, 1966, p.221.
5. WHO Handbook on human nutrinonal requirements. Geneva, Monograph series No. 61, 1974.
6. Wetherill, G. B. Elementary statistical method. Chapman K Hall Hall, London, Willey,  1981, p.224.
7. Stuart, H. C. and Stevenson, S. S. Physical growth and development, in Textbook of  pediatrics. Edited by Waldo E. Nelson 7th ed. Philadelphia, Saunders, 1959, p. 12.
8. Venkatachalam, P.S. Maternal nutritional status and its effect on the newborn. Bull. WHO., 1962; 26: 193.
9. Bhatia, B. D., Tyagi, N. K., Handa, P. Relationship of low-birth weight anthropomerry  maternal weight - height indices. Indian J. Med. Res.. 1985; 82;374-6.
10. Shiono, P. H., Kiebanoft, M. A., Granbard, B. 1., Berendes, H. W. and Rhoads, G.G.  Birthweight among women of different ethnic group. AMA., 1986; 225: 48.
11. Ladipo and Adelusia, B. Birth weight of Nigerian children at Ibadan, East Afr. Med. J.,  1977;54:31.
12. Rehan, N. E., Tafida, D. S. Lowbirth weight in Hausa Infants. Niger. J. Paedian., 1981; 812; 35-9.
13. Bissenden,J. G.,Scott, P. H., King,J., Hallum,J., Mansfield, H. N. and Wharton, B. A.  Anthropometric and biochemical changes during pregnancy in Asian and European mothers having  light for gestations! age babies. Br. J. Obscec. Gynaecol., 1981; 88,999.
14. Bissenden, J. G., Scott, P. H., Hallum, J., Mansfield, H. N.and Wharton, B. A.  Anthropometric and biochemical changes during pregnancy in Asian and European mothers having  well grown babies. Br. J. Obstet. Gynaecol., 1981; 88; 992.
15. Rush, D., Stein, Z. and Susser, M. A randomized controlled trial of prenatal nutritional  supplementation in pregnancy in New York city. Pediatrics, 1980; 65;685.
16. Viegas. O.A.C., Scott, P. H., Cole, T.J., Eaton, P., Needham, P. G. and Wharton, B. A.  Dietary protein energy supplementation of pregnant Asian mothers at Sorrento, Birmingham. II. Selective during third trimester only. Br. Med.J., 1982; 285:592.
17. Falkner, F. Maternal nutrition and fetal growth. Am.J. ClIn. Nutr., 1981; 34: 769.
18. Leching, A., Habicht, J. P., Deigado, H., Klein, 8. E., Yarbrough, C. and Martorell, R.  Effect of food supplementation durlngpregnancyon birthwelght. Pediatrics, 1975;56: 508.
19. Blackwell, 8.0., Chow, B. F., Chinn, K.S.K., Blackwell, B. and Hsu, S.C. Prospective  maternal nutrition study in Taiwan; rationale, study design, feasibility and preliminary  findings. Nutr. Rep. Int., 1973; 517.
20. Prentice, A. M., Whitehead, R. 0., Wackinson, M. and Lamb, W. H. Prenatal dietary supplementation of African women and birthweight. Lances, 1983; 1: 489.
21. Newcombe, It. G. Nonnutritional factors affecting fetal growth. Am. 3. Clin. Nutr.,1981; 34:732.
22. Raman, L Influence on maternal nutritional factors affecting birthweighs. Am. J. din. Nutr., 1981; 34:775.
23. Dougherty, G.R.S., Jones, A. D. The determinants of birthweight. Am. 3. Obstet. Gynecol., 1982; 144: 190.
24. Van den Berg, B. J. Maternal variables affecting foesal growth. Am. J. dim. Nutr.,1981: 34:722.
25. Robertson, E. and Monkus, 8. Method to determining nutrient requirements in pregnancy-II. Am.J. dIm. Nutr., 1981; 34:705.
26. Lun, K.C., Tan, N. It., Mughes, K. Multivariate analysis ofSingapore birshweight. Asia OceaniaJ. Obstes. Gynaecol., 1985; 11: 189.
27. Comstock, 6. W., Shah, F. K., Meyer, M. B. and Abbey, H. Low birth weight and neonatal mortality rate related to maternal smoldngand socioeconomic status. Am. J.Obstet. Gynecol., 1971; 111:53.
28. Effong, CE., Laditan, A. A. 0., Almakhu, V. E. and Ayeni, 0. Ulster Med.J., 1976; 45:210.
29. Vuori, L, Christiansen, N., Clemens, J., Mont, J. 0., Wagner, M. and Heifer, H. 6. Nutritional supplementationand outcome ofpregnancy. II. Visual habituation at 15 days. Am.J.Clin. Nutr., 1979; 32: 463.
30. Frisancho, R., Matos, J. and Flegel, F. Maternal nutnnnnas status anu adolescem pregnancy outcome. Am.J. dim. Nutr., 1983:38:739.
31. O\'Sultivan, J.B., Gellis, S.S.and Tenney, B.0. Aspects of birthweight and its influencing variables. Am.J. Obstet. Gynecol., 1965:92: 1023.
32. Mora,J.0., de Paredes, B., Wagner, M., de Navorro, L., Suescun,J., Christiansess, N. and Herrera, MG. Nutritional aupplemcntation and the outcome of pregnancy. I.Birthweight. Am.J. dim. Nutr., 1979: 32:455.
33. Naeyes, R.L. Nunisional/nonnutritional interactions that affect the outcome of pregnancy. Am. J. dim. Nutr., 1981; 34:727.
34. Chamberlain, 6. Effect of workduring pregnancy. Obstet. Gynecol., 1985:65:747.
35. Tafari, N., Naeye, R.L. and Gobezie, A. Effects of maternal undensuttition and heavy physical work during pregnancy on birth weight. Br. J. Obstes. GynecoL, 1980; 87:222.
36. Hassan,T.J., Ibrahim, K. andJafarey, SN. Excessive phyaicalworkduringpregnancy and birthweighs. Asia Oceania J. Obsses. Gynccol., 1990; 16,17.
37. Lubchenco, L.O., Mansman, C., Dressier, M. and Boyd, F. Intrauterine growth as estimated from liveborn birth-weight data at 24-42 weeka of gestation. Pediatrics,1963; 32:793.

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