Antepartum prediction of the postmature infant

A prospective investigation was undertaken to determine whether present antepartum methods of fetal assessment were useful in predicting postmaturity. Thirty-two (22%) of 147 strictly defined postdate pregnancies produced infants with signs of postmaturity. Clinical findings, fetal heart rate testing (primarily nonstress tests), and fetal movement charting were not found to be reliable predictors. Single-voiding estrogen:creatinine (E:C) ratios were significantly (P less than .0001) lower in fetuses with subsequent findings of postmaturity than in those without such signs, and all subnormal values were associated with postmature infants. Twenty-four of 29 pregnancies with oligohydramnios diagnosed by ultrasonography produced postmature infants, whereas 110 of 118 pregnancies with either pockets or an adequate volume of amniotic fluid produced infants who were not postmature. Of the fetal surveillance methods used in the authors' clinic, subnormal E:C ratios and ultrasonic evidence of oligohydramnios were the most reliable predictors of postmaturity.