Fetal presentation and successful twin vaginal delivery

Despite the demonstrated safety of a trial of labor for pregnancies with a vertex-presenting twin and clinical guidelines in support of this plan, the rate of planned cesarean delivery for twin pregnancies remains high. This high rate, as well as variation in cesarean rates for twin pregnancies across providers, may be influenced strongly by concern about delivery of the second twin, particularly when it is in a nonvertex presentation. There are limited data in the literature that has examined the impact of the position of the nonpresenting twin on successful vaginal delivery or maternal/neonatal morbidity.

We hypothesized that nonvertex presentation of the second twin would be associated with lower rates of successful vaginal birth for those patients attempting labor.

This institutional review board-approved, retrospective cohort study of women who labored with twin pregnancies in a single urban hospital from 2007-2011. We included women with vertex-presenting first twins at >32 weeks gestation without a contraindication to labor and excluded those with uterine scar or lethal fetal anomaly. Vaginal delivery rates were evaluated according to vertex or nonvertex presentation of the second twin at admission and again at delivery. Maternal and neonatal morbidities were evaluated separately. Logistic regression was used to control for multiple confounders.

Seven hundred sixteen patients met the inclusion criteria; 349 patients (49%) underwent a trial of labor. This included 73% (296/406) of eligible vertex/vertex twins and 17% (53/310) eligible vertex/nonvertex twins (P < .01). When compared with laboring patients with vertex/vertex-presenting twins, those with vertex/nonvertex twins were younger (median age, 32 vs 33 years; P = .05), were more often multiparous (60% vs 43%; P = .02), and were less likely to have hypertension (13% vs 27%; P = .03). Eighty-five percent of patients with nonvertex second twins at admission delivered vaginally, compared with 70% of patients with vertex second twins (P = .02). After we controlled for confounders, the difference was not statistically significant (adjusted odds ratio, 2.10; 95% confidence interval, 0.93-4.73). In the subset of patients with nonvertex second twins at delivery, those who initiated labor had an 89% vaginal delivery rate, compared with a 56% rate for those who changed from vertex to nonvertex presentation during labor (adjusted odds ratio, 19.90; 95% confidence interval, 3.86-102.78). Labor induction and increasing provider years in practice were also significant positive predictors of vaginal birth when the second twin was nonvertex at delivery. Maternal and neonatal morbidity was low and similar between groups, although 8% of women with nonvertex second twins experienced cervical lacerations, compared with 1% with vertex second twins (P = .01).

Patients with nonvertex second twins had comparable, if not higher, rates of vaginal delivery than their vertex-presenting counterparts. The higher rate of vaginal delivery with stable nonvertex lie and the association with labor induction and the physician's years in practice all suggest a role for provider selection and delivery planning. These findings and the observed 11% rate of intrapartum presentation change support vaginal delivery of the nonvertex second twin.