Maternal lean body mass may be the major determinant of birth weight: a study from India

Abstract

This study explored the relationship of maternal body composition parameters to the birth weight of the offspring. Maternal anthropometric parameters (weight, height) and body composition by dual energy X-ray absorptiometry were measured in 76 women from low-income group during 12–21 days postpartum. The mean±s.d. height, weight of the mothers and birth weight of the newborns were 151.5±5.29 cm, 46.7±6.04 and 2.84±0.358 kg, respectively. When the relationship of maternal anthropometric and body composition parameters to the infants' birth weight was studied, maternal lean body mass was found to be the most important determinant of birth weight (R2 (%)=21.3) (P<0.001). This study highlights the importance of increasing lean body mass in young women for better pregnancy outcome.

Introduction

Birth weight is an important determinant of infants' well-being and low birth weight (LBW) is known to increase the risk of adult onset chronic diseases (Yajnik, 2001; Barker, 2004). The mean birth weight among the low socioeconomic group of women in India is around 2.7 kg and one-third of these newborns are LBW (<2.5 kg) (UNICEF, 2004).

It is well established that maternal nutritional status has a significant influence on the birth weight of the baby (Kramer, 1987; Naidu and Rao, 1994; Thame et al., 2004). Studies from India and other parts of the world have demonstrated the role of pre-pregnant weight and weight gain during pregnancy on the fetal size (Raman et al., 1995; Ehrenberg et al., 2003; Ronnenberg et al., 2003). However, very few studies from India have explored the role of components of maternal weight, that is, fat mass and lean mass on the infant's birth weight. A study was therefore carried out to explore the role of maternal body composition on the birth weight of the newborn.

Subjects and methods

Seventy-six women who delivered in a large Government Maternity Hospital (Hyderabad, India) and came to the Nutrition Unit for their first follow-up during the period of January 2002 to September 2002 were recruited consecutively for this study. None of them refused. Most of the women visited the unit on days 12–21 postpartum. Background information was collected and maternal weight was measured without footwear to the nearest 0.1 kg on lever type SECA balance (Hamburg, Germany). Heights were measured to the nearest 0.1 cm with a stadiometer (SECA, UK). Body composition was assessed at the same time by dual energy X-ray absorptiometry (Hologic 4500 W, Waltham, MA, USA), which is one of the latest technologies with high precision. Birth weights were recorded from the delivery notes. Validity of the recorded birth weights was assured by calibration of the instrument and calculating intra- and inter-individual variations.

Statistical analysis

SPSS 11.5 Windows version was used for statistical analysis. Descriptive statistics were calculated for all the parameters. Mean values were compared by analysis of variance across tertiles for all parameters with post hoc least significance difference tests. Trends for proportions were also calculated across tertiles of maternal body composition parameters using χ2 test. Correlation coefficients were used for studying the relationships. Multiple linear regression analysis was used to study the variations in outcome variable with independent variables.

Results

The women enrolled for the study lived in urban slums and were employed in the non-formal sector. They belonged to the lowest socioeconomic strata of society and were working as servant maids, piece rate workers, home-based occupations, etc., which are not governed by the state labour laws. All of them had singleton full-term vaginal deliveries. The mean (±s.d.) age (years), parity, height (cm), weight (kg), body mass index (BMI) of the women were 23.2 (±2.86), 2.8 (±0.88), 151.5 (±5.29), 46.7 (±6.04) and 20.4 (±2.41), respectively. Their mean (±s.d.) lean mass, fat mass and per cent fat were 30.6±3.30, 13.5±3.96 kg and 29.1±5.24%, respectively. The mean (±s.d.) birth weight of the babies was 2.84 (±0.358) kg and 21% of them were LBW babies.

When the mean birth weight and proportion of LBW babies were assessed as per the tertiles of maternal weight, BMI, lean mass, fat mass and per cent fat (Table 1), it was observed that birth weights increased and proportion of LBW babies decreased significantly with increasing tertiles of maternal weight (P<0.01), BMI (P<0.05), lean mass (P<0.05) and fat mass (P<0.05), but there were no changes in birth weight or proportion of LBW in relation to tertiles of per cent fat of the mothers. When the relationship of maternal age, parity, anthropometric and body composition parameters to the birth weight was investigated, all the above variables except maternal age, parity and per cent fat had significant positive relationship to birth weight (P<0.05) and were related to each other (Table 2). When regression models were constructed with birth weight as a dependent variable and maternal age, parity, height, weight, BMI, lean mass, fat mass and per cent fat as independent variables, 26.7% (P<0.001) of the variation was explained by these variables, but maternal lean mass accounted for the major variation in birth weight (R2(%)=21.3) (P<0.001).

Table 1 Mean±s.d. birth weights in kg and per cent LBW infants (in parentheses) as per the tertiles of maternal weight, BMI, lean body mass, fat mass and per cent fat (N=76)
Table 2 Interrelationships between BW, MW, MH, maternal BMI, LBM, FM and PF

Discussion

This is an important study from India, which explores the relationship between maternal body composition and infant's birth weight. The significant finding is that the maternal lean mass may be the major determinant of birth weight. Similar findings have been reported earlier from other populations (Briend, 1985; Langhoff-Roos et al., 1987).

Anthropometric characteristics of the mothers were similar to the results of the large-scale nutrition surveys carried out by National Nutrition Monitoring Bureau (NNMB Report, 2002) and therefore representative of the low-socioeconomic group in India. However, all these parameters were much below the Western values.

It is known that pregnant women from this socioeconomic group in India gain around 6 kg weight during pregnancy (Annual Report, 2002). The components of weight gain such as fetus, placenta, amniotic fluid, excess blood volume, uterine hypertrophy, etc. are lost at birth and during the postpartum period owing to involution of the tissues. As the mother is not known to put on lean body mass during pregnancy, it may be speculated that maternal weight at 15 days postpartum represents pre-pregnant weight plus additional weight gained during pregnancy (usually fat stores) (Hytten, 1991; Alam et al., 2003). As fat mass was not the major determinant of birth weight in this study, one may speculate that maternal pre-pregnant weight may be important for fetal outcome. Earlier studies have also demonstrated that pre-pregnant maternal energy reserves may be an important determinant of fetal growth (WHO, 1995; Neggers and Goldenberg, 2003) as partitioning of nutrients between mother and offspring seems to depend on prior maternal nutritional status (Young and Young, 1985).

Earlier studies from the same population group (Raman et al., 1995; Annual Report, 2003) indicated that pre-pregnant weight of <41 kg and BMI of <18.5 kg/m2 were associated with a higher incidence of LBW. It may be possible to arrive at a cutoff for prediction of LBW based on maternal body composition.

Dietary supplementation during pregnancy with resultant maternal weight gain and markedly increased birth weight was demonstrated in conditions of acute food shortage (Stein et al., 1975; Rayco-Solon et al., 2005). However, under conditions of chronic undernutrition, supplementation of energy, proteins as well as micronutrients to the level of recommended dietary allowance during pregnancy resulted in only marginal improvements in birth weight (Christian et al., 2003; Kramer and Kakuma, 2003). The limited efficacy of these supplements may be owing to the inability of the body to lay down lean mass during pregnancy, because pregnancy is too short a window to increase lean mass.

The strengths of this study are the fact that the study group is representative of low-socioeconomic group population of India and possibly other Asian countries, and the use of a sensitive technique of DXA for body composition assessment. The limitation of this study is the lack of data on pre-pregnancy weight and comparable data on women from other socioeconomic groups.

It is known that the high body fat percentage and low lean body mass in Asians increases the risk of chronic diseases (Misra and Vikram, 2002). Studies by Briend (1985) have shown the inverse relation of maternal body fat to the birth weight. Our study, however, draws attention to the reproductive consequences of low lean body mass. A recent study from this institute has shown that micronutrient supplementation in adolescent children consuming adequate energy resulted in increase in height and lean body mass (Shatrugna et al., 2006). It may be important in Asian countries to plan nutritional intervention programmes to improve the lean body mass of young women for a better reproductive performance.

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Acknowledgements

We would like to place on record the support and encouragement of Dr B Sivakumar, Director, National Institute of Nutrition, Hyderabad. We are thankful to Mr AN Naidu, Deputy Director (Retired), National Institute of Nutrition, Hyderabad, Professor K Ramachadran, Chennai and Dr AV Kurpad, Professor, St John's Medical College, Banglore, who reviewed the manuscript and gave valuable suggestions. We are also grateful to Ms Usha Rani, Mr Sambasiva Rao, Ms Prema Kumari, Ms Sundaramma and Ms Malini V Rao for their help during the course of the study. This study would not have been possible without the unstinted cooperation of the women who were the subjects of the study and we are grateful to them.

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Correspondence to V Shatrugna.

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Guarantor: Dr V Shatrugna.

Contributors: BK and VS contributed to the study design, subject recruitment, interpretation of the results and manuscript preparation. NB carried out the statistical analysis of the data.

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Kulkarni, B., Shatrugna, V. & Balakrishna, N. Maternal lean body mass may be the major determinant of birth weight: a study from India. Eur J Clin Nutr 60, 1341–1344 (2006). https://doi.org/10.1038/sj.ejcn.1602461

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Keywords

  • maternal weight
  • maternal body composition
  • birth weight
  • Indian women

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