The association of maternal weight with cesarean risk, labor duration, and cervical dilation rate during labor induction.
OBJECTIVE
To assess the relationship among maternal weight and cesarean delivery, cervical dilation rate, and labor duration.


METHODS
We used a secondary analysis of 509 term women who were previously enrolled in a prospective observational study of a labor induction protocol in which standardized criteria were used for labor management. A variety of analyses were performed, both unadjusted and adjusted. P <.05 was considered significant.


RESULTS
The mean +/- standard deviation weight of women who underwent a cesarean (97 +/- 29 kg) was significantly higher than that of women who were delivered vaginally (87 +/- 22 kg, P <.001). In a logistic regression model of nulliparas who comprised 71% of the study population, after adjustment for the confounding effects of infant birth weight, maternal age, initial cervical dilation, and diabetes, for each 10-kg increase in maternal weight, the odds ratio for cesarean delivery was significantly increased (odds ratio 1.17; 95% confidence interval 1.04, 1.28). In a linear regression model also limited to nulliparas and after adjusting for the same confounders, the rate of cervical dilation was inversely associated with maternal weight: for each 10-kg increment, the rate of dilation was decreased by 0.04 cm/h (P =.05). Similarly, labor duration was positively associated with maternal weight: for each 10-kg increment, an increase in the oxytocin to delivery interval of 0.3 hours was observed in nulliparas (P =.02). Neither lower rates of oxytocin administration to heavier women nor diminished uterine responsiveness (as reflected in measured Montevideo units) accounted for the slower labor progress.


CONCLUSIONS
In nulliparous women undergoing labor induction, maternal weight was associated with a higher cesarean risk and longer labor and was inversely proportional to the cervical dilation rate.


METHODS
II-2
Center for Research in Women's Health, Department of Obstetrics and Gynecology, University of Alabama at Birmingham, 619 19th Street South, OHB 451, Birmingham, AL 35249-7333, USA. francis@nuthalapaty.net
Francis S
FS
Nuthalapaty
Dwight J
DJ
Rouse
John
J
Owen
D000328:Adult; D001835:Body Weight; D002585:Cesarean Section; D005260:Female; D006801:Humans; D007747:Labor Stage, First; D007751:Labor, Induced; D010298:Parity; D011247:Pregnancy; D012189:Retrospective Studies; D012307:Risk Factors; D013997:Time Factors; D014219:Trial of Labor