(397) Impact of Parity on Perinatal Outcomes Following Shoulder Dystocia

Shoulder dystocia (SD) remains an obstetric emergency with potential for significant neonatal and maternal harm. While fetal size and delivery mode are often emphasized, the role of parity is less understood. This study aimed to evaluate perinatal outcomes following SD, comparing nulliparas and multiparas.

Study Design:

A secondary analysis of the Assessment of Perinatal Excellence (APEX) database, including all singleton deliveries ≥ 37 weeks complicated by SD. Individuals with fetal malformations or fetal demise were excluded. The primary outcome was a composite neonatal adverse outcome (CNAO), including cardiorespiratory resuscitation within 24 hours, birth-related neonatal injury, and neurological outcomes. The secondary outcome was a composite of maternal adverse outcomes (CMAO), including 3rd or 4th degree perineal tear, cervical tear, estimated blood loss ≥ 1,000 cc, and blood transfusion. Poisson regression was used to calculate adjusted relative risk (aRR) with 95% confidence intervals (CI).

Results:

Of the 115,502 patients in the parent study, 2,091 (2%) met inclusion criteria: 753 (36%) were nulliparous, while 1,338 (64%) were multiparous. Nulliparas were younger, had lower rates of gestational diabetes mellitus (GDM) and neonatal macrosomia, as well as higher rates of operative delivery and later gestational age at delivery. CNAO rates were higher among nulliparas (aRR 1.49, 95% CI 1.20-1.84), including a higher rate of brachial plexus injury (aRR 2.60, 95% CI 1.52-4.46; Table 1). Lower Apgar scores and higher rates of neonatal intensive care unit admission were noted as well. CMAO rates was higher among nulliparas (aRR 2.40, 95% CI 1.86-3.10), driven mainly by higher rates of 3rd or 4th degree tear (Table 2).

Conclusion:

Among term singletons with SD, nulliparity was associated with higher rates of adverse neonatal and maternal outcomes, including over twice the rate of brachial plexus injury as well as a 3rd/4th degree tear in 1 of 6 cases. These findings underscore the importance of individualized risk assessment and may support enhanced preparedness during delivery for nulliparas.