Relationship of gestational age and cervical dilation to the timing of delivery

To determine the effect of gestational age and cervical dilation on pregnancy continuation in women with idiopathic preterm labor who were treated with parenteral tocolysis.

A total of 950 women with singleton gestations, intact membranes and preterm labor treated with tocolysis prior to 34 weeks' gestation were retrospectively studied. These women were identified from the March of Dimes prematurity prevention program database. For analysis, women were categorized into five gestational age groups and three cervical dilation groups. The primary outcomes measured were the percentage of women who remained undelivered at 48 h and at 14 days post-initiation of therapy.

Overall, 82% of women remained undelivered after 48 h and 65% remained undelivered at 14 days. As cervical dilation advanced, the number of women remaining undelivered at 48 h and 14 days significantly decreased. However, even at > or = 4 cm, 52% of women remained undelivered at 48 h. If the cervix was dilated < 2 cm, gestational age did not influence the number of days gained prior to delivery. However, if the cervix was dilated > or = 2 cm, women at < 25 weeks' gestation were more likely to deliver compared to women at the same dilation but with more advanced gestational ages.

Overall, 82% of women in preterm labor and 52% of those presenting with > or = 4-cm cervical dilation, delivered after 48 h. Therefore there appears to be ample opportunity for most women in preterm labor with intact membranes, even those at advanced dilations, to receive a complete course of corticosteroid therapy.