Examining pre-term birth and cesarean section rates in gestational carrier pregnancies

This study sought to report on the route and gestational age at delivery of gestational carrier (GC) pregnancies with respect to the GCs' prior obstetric history.

A retrospective analysis of all GC pregnancies from one of the largest surrogacy agencies in California between 2008 and 2018 was performed. Available demographic data and obstetric history, including a history of prior cesarean section (CS) and preterm birth (PTB), were collected for each GC and correlated to outcomes of the index GC pregnancy. Primary outcomes for the index GC pregnancies included delivery route and gestational age at delivery.

Eight-hundred-thirty-six GCs were included in our analysis. 319 (38.2%) delivered via CS, and 517 (61.8%) delivered vaginally. 60 (18.8%) of the CS deliveries were due to multifetal gestation. Primary CS rate in singleton GC pregnancies was 38.5%. In women without a history of CS, neither age, BMI, interpregnancy interval, prior parity, nor year of delivery impacted the primary singleton CS rate (all, P > 0.05). Of GCs with a history of a prior CS (n = 350, 41.9%), 218 (62.3%) had a vaginal delivery after CS (VBAC) and 132 (37.7%) had a repeat CS. Women who had successful VBACs were significantly younger than those who had repeat CS (mean 33.7 vs. 35.2 years, P = .003). BMI was lower in patients who had a VBAC compared to those that had a repeat CS (mean BMI 24.6 vs. 25.5, P = 0.074), although this did not reach statistical significance. In GCs with a history of CS, interpregnancy interval, year of delivery, prior parity, and multiple gestation in the index GC pregnancy did not impact mode of delivery. VBAC rates did not change over the study period (P = 0.757). Overall PTB rate was 15.1%. Most PTB in GC pregnancies were in those with a history of PTB, and PTB was more likely in singletons rather than multifetal gestations (76.7% in singletons vs. 30% in multiples) in patients with history of PTB (P < 0.001). Those with no history of PTB and who carried multiples had a low rate of PTB; in fact, in this group, only 1 out of 35 patients had a PTB with multiples.

Both primary CS and PTB rates in singleton GC pregnancies are higher than national averages. CS rates are independent of age, BMI, and interpregnancy interval. In GCs with a history of a CS, VBAC rates well exceed national averages and are higher in younger GCs with a lower BMI. PTB rates are impacted primarily by the GCs obstetric history. In those GCs without a history of PTB, rates of PTB are low, even in those with a multifetal gestation.