Comparison of outcomes in uncomplicated term and post-term pregnancy following spontaneous labor.

This study was designed to compare outcomes of spontaneous labor in uncomplicated term and post-term pregnancy. It comprised of a case matched study of 285 women with uncomplicated singleton post-term pregnancy (290-301 days of gestation) and 855 women with uncomplicated singleton term pregnancy (259-287 days of gestation). Term controls were matched to post-term cases on a 3:1 basis. The main outcome measures were cesarian section, Apgar scores and admission to the Neonatal intensive care unit (NICU). Cesarian section was significantly more common in women with post-term pregnancy (Relative Risk = 1.90, 95% CI = 1.29-2.85). The increase was equally distributed between cesarian sections performed for failure to progress in labor (RR = 1.74, 95% CI = 1.02-3.04) and fetal distress (RR = 2.00, 95% CI = 1.14-3.61). There were no differences in low Apgar scores, but admission to the NICU was more common in the post-term group (RR = 2.69, 95% CI = 1.39-5.54). There was no difference in significant neonatal pathology in either group. Uncomplicated post-term pregnancy is associated with increased rates of obstetric and neonatal interventions in terms of cesarian section and NICU admissions. This effect does not appear to be a result of underlying pathology associated with post-term pregnancy. We suggest that a lower threshold for clinical intervention in pregnancies perceived to be "at-risk" may be a significant contributing factor.