Academic journal article Journal of Health Population and Nutrition

Bioelectrical Impedance among Rural Bangladeshi Women during Pregnancy and in the Postpartum Period

Academic journal article Journal of Health Population and Nutrition

Bioelectrical Impedance among Rural Bangladeshi Women during Pregnancy and in the Postpartum Period

Article excerpt

INTRODUCTION

Bioelectrical impedance analysis (BIA) is widely used in evaluating body-composition in epidemiological studies and clinical settings (1-4), usually by applying measures of resistance or impedance to population-specific, predictive equations for estimating total body-water (TBW), fat-free mass (FFM), and fat mass. Such equations have primarily been derived within well-nourished populations in developed-country settings (5-9). Application of BIA to determine body-composition in undernourished populations has been less common.

In South Asia, equations exist for predicting TBW in children aged 6-12 months (10) and school-age pre-adolescent Indian children (11,12) and fat mass in Indian men (13). The use of BIA for body-composition among South Asian women has been largely confined to groups of immigrants in other countries (5,14). Even fewer data are available describing BIA properties during pregnancy or lactation in any South Asian populations, possibly due to uncertainty of the value of BIA in assessing the health or nutritional status in the absence of population-specific equations for body-composition (14). Additionally, complex relationships between intra- and extra-cellular water and foetal and maternal nutrition and body mass compartments challenge the validity of BIA for estimating body-composition during pregnancy (15-17). Population studies of BIA, on the other hand, are emerging that describe distributions of resistance (R), reactance (Xc), and impedance (Z) in normal pregnancy in developed countries and reveal their potential to reflect risk of pregnancy-related complications. In Italian mothers, for example, Ghezzi et al. found that second trimester BIA indices were predictive of birthweight (17).

Maternal BIA could be particularly useful in South Asia where malnutrition and adverse pregnancy outcomes, including intrauterine growth retardation and preterm birth, are prevalent (18). Investigating relationships of pregnancy and health outcomes directly with BIA properties eliminates the need to derive estimates of body-composition. Further, BIA data obtained in large population studies could improve the understanding of the public-health use of BIA, especially where predictive equations based on sophisticated methods of body-composition measurement are unavailable.

The present study was designed to generate and compare normative cross-sectional distributions of bioelectrical impedance properties in early pregnancy, late pregnancy, and at three months postpartum in a cohort of women with viable pregnancies or live infants at the time of analysis in a typical rural setting in northern Bangladesh.

MATERIALS AND METHODS

Population and study design

This study was nested within a large randomized community-based trial evaluating vitamin A and beta-carotene supplementation on all-cause, pregnancy-related maternal and infant mortality in northwestern Bangladesh during August 2001-February 2007 (19,20). Pregnancies were identified by registering married women of reproductive age and enrolling them into a five-weekly, home-based surveillance system, with a human chorionic gonadotrophin-based urine test confirming pregnancy among women reporting 30 consecutive amenstrual days. Data presented here were collected in a contiguous substudy area of 22 sq km with an estimated population of ~42,000, where pregnancies were enrolled and followed by the standard protocol but with additional clinical, anthropometric, biochemical and body-composition assessments done. Inclusion requirements for results reported here were provision of a valid BIA measurement obtained from women meeting the following criteria: (a) an early-pregnancy measurement taken within the first 12 weeks of gestation (first trimester); (b) a late-pregnancy measurement obtained between 32 and 36 weeks of gestation, inclusive (third trimester); or (c) a postpartum measurement obtained between 12 and 18 weeks postpartum, inclusive, among women with a living infant at the time of the visit. …

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