The timing of maternal weight gain during pregnancy and fetal growth

The morbidity, mortality, and growth patterns of intrauterine growth retard ed (IUGR) infants vary according to body proportionality, or the ponderal i ndex. Much less in known, however, about the factors that give rise to the various forms of IUGR. This study tests that hypothesis that the rate of ma ternal weight gain during early/mid and late pregnancy are differentially r elated to body size and proportions at birth in a nutritionally stressed po pulation in rural Malawi. The data consist of prospectively collected measu rements of maternal weight and infant size at birth on 272 mother-infant pa irs. The results reveal that early/mid and late weight gain are both relate d to birth weight and length, but not to the ponderal index. Late weight ga in is particularly predictive of infant size among thin women (BMI less tha n or equal to 18.5) and is several times stronger than early/mid weight gai n. These findings do not support the timing hypothesis as previously stated in the literature, but do add to the suggestions arising from a disparate literature that growth acceleration in length may precede acceleration in w eight-for-length during a period of nutritional replection in phases of the life cycle characterized by rapid growth. (C) 1999 Wiley-Liss, Inc.