Influence of maternal age, birth-to-conception intervals and prior perinatal factors on perinatal outcomes.

This study evaluated the influence of prior perinatal factors on birth weight, length of gestation, and maternal pregravid and postpartum weights in subsequent pregnancies. The study sample included 47 women each with first, second and third pregnancies. Mean pregravid weight increased by 5.2 lb between the first and second pregnancies and by 4.4 lb between the second and third pregnancies. Total weight gain averaged 31 lb for the first pregnancy and 28.4 and 28.3 lb for the second and third pregnancies, respectively. Mean birth weight increased by 111 g between the first and second pregnancies and by 199 g between the second and third pregnancies. Mean gestational age was similar for all three pregnancies, averaging 39.5 weeks. Using stepwise forward multiple regression analyses, we determined that birth weight and length of gestation are both influenced significantly by prior birth weight and length of gestation; subsequent pregravid weight is influenced significantly by prior rate of gain, pregravid weight and postpartum weight; and postpartum weight is significantly influenced by prior rate of gain and birth weight. Comparisons across three pregnancies for the same woman showed that differences in birth-to-conception interval were not associated with higher postpartum weight or subsequent pregravid weight. These data indicate that in healthy, nonsmoking, low-risk women, the maternal and infant outcomes of pregnancies are significantly influenced by prior outcomes but not by either short birth-to-conception interval or greater maternal age.