Maternal pre-pregnancy weight and placental weight determine birth weight in normal Jamaican infants

Birth weight is related to neonatal health and long-term risk of chronic di sease. Since animal studies have shown that birth outcome is related to pla cental function, the present was designed to explore the relationship betwe en birth weight and placental growth and composition with maternal factors during pregnancy among normal term pregnancies in 51 primiparous and 40 mul tiparous women delivering at the University Hospital of the West Indies. Bo th groups were followed from 15 weeks of gestation to term. The primiparous group was generally younger than the multiparous (mean age 22+/-4 versus 3 1+/-5 yr).They were significantly lighter (55+/-8 versus 61+/-9 kg) with a lower body mass index (21+/-3 versus 23+/-4kg/m(2)) during early pregnancy but gained more weight during pregnancy, 11 kg compared with 8 kg, respecti vely. The duration of pregnancy was similar for both groups. Although the s ize of the placenta was not significantly different between the two groups, the mean weight of the multiparous placentae was more than that of the pri miparous placental. Also, for all mothers both placental weight and initial maternal weight related directly to birth weight. Placental non collagen p rotein (NCP), sodium and potassium contents were significantly higher for m ultiparous women and were related to birth weight. The primiparous group ha d babies who were significantly lighter, 3.03 kg compared with 3.36 kg, for the multiparous and this could be attributed to differences in placental f unction and maternal weight, parity no longer explained any of the differen ces in birth weight. It is concluded that maternal body weight at the time of becoming pregnant and the early development of the placenta determine th e efficiency with which nutrients might be delivered to the foetus and henc e foetal growth. The difference in birth weight between primiparous and mul tiparpus women can be explained by the differences in maternal weight at th e time of becoming pregnant.