804: Large-for-gestational age infants – when is it truly labor dystocia?

Abstract

Labor dystocia is a diagnosis often given to women with large-for-gestational age (LGA) infants with a prolonged first stage of labor, ultimately leading to cesarean delivery. However, normative standards for the first stage of labor when fetal macrosomia is suspected have not been clearly defined. This study aimed to evaluate labor progress of women with LGA infants compared to appropriate-for-gestational age (AGA) infants. We conducted a retrospective cohort study of patients admitted for labor at our institution from 2004 -2014 with a vertex singleton at term who achieved 10cm cervical dilation. Labor curves were constructed with repeated measures regression and were compared between patients who delivered LGA infants (actual birthweight [BW] >90th percentile) and those who delivered AGA infants (actual BW 10-90th percentile). Interval-censored regression estimated median duration of labor stratified by actual infant BW, and further stratified by parity (nulliparity vs. multiparity) and labor type (spontaneous vs. induction of labor). Among all 17,097 women, 15843 (92.7%) had AGA infants, of whom 6194 (39.1%) were nulliparous and 5351 (33.8%) were induced; 1,254 (7.3%) had LGA infants, of whom 387 (30.9%) were nulliparous and 464 (37.0%) were induced. After adjustment for obesity, epidural and prior cesarean delivery, AGA infants progressed to 10cm significantly faster than LGA infants, even when stratified by maternal parity and labor type (p<0.01). Patients with LGA infants progressed from 4-10cm more slowly than with AGA infants (median 7.4 hours [5th-95th percentile, 2.2-5.8] vs. 4.9 hours [1.4-16.9], p<0.01). LGA infants also progressed in active labor from 6-10cm more slowly than with AGA infants (2.4 [0.4, 13.5] vs. 1.7 [0.3, 9.2], p<0.01). In the LGA group, nulliparous women dilated 4-10cm more slowly than multiparous women (8.3 hours [2.5-27.7] vs. 5.9 hours [1.6-21.4]). Women in spontaneous labor also dilated 4-10cm faster than induced women in the LGA group (6.2 hours [1.8-21.5] vs. 7.3 hours [2.0-26.7]). Women with LGA infants experience relatively slowed labor progression compared to women with AGA infants, particularly in nulliparous and induced women. Clinicians should consider fetal size and make labor dystocia diagnoses cautiously in women with suspected fetal macrosomia.View Large Image Figure ViewerDownload Hi-res image Download (PPT)