A vaginal delivery, often referred to as a “natural birth,” is a possible option for women expecting twins, but it depends on a strict set of medical conditions. Attempting a vaginal delivery requires a comprehensive medical assessment to ensure the safety of both the mother and the babies. The presence of two fetuses introduces unique variables, meaning a planned Cesarean section is often the safer, more frequent alternative. The feasibility of a vaginal twin delivery hinges on multiple factors related to the babies’ positions, gestational age, and overall health.
Essential Criteria for Considering Vaginal Delivery
The most important factor determining the possibility of a vaginal twin delivery is the position of the first baby, Twin A, which must be head-down (cephalic) for the attempt to be considered safe. When Twin A is positioned head-first, it effectively dilates the cervix, creating a clear pathway for the second twin to follow. The position of the second twin, Twin B, is less restrictive, as medical techniques can sometimes be used to assist its delivery even if it is not head-down.
Another significant consideration is the gestational age at which the delivery occurs, as this affects the babies’ maturity and their ability to tolerate labor. For dichorionic twins, who have separate placentas, delivery is often planned around 37 to 38 weeks of gestation. Monochorionic twins, who share a single placenta, are delivered slightly earlier, usually between 36 and 37 weeks, to mitigate the increased risk of certain late-term complications.
The estimated weights of the twins and the degree of difference between them is also assessed, as a significant weight discordance can complicate the delivery. If the estimated fetal weight difference between the twins is greater than 20%, a vaginal birth may be deemed too risky. Furthermore, twins who share both a placenta and an amniotic sac, known as monochorionic-monoamniotic (MoMo) twins, are excluded from a trial of labor due to the high risk of cord entanglement.
Unique Management During Twin Vaginal Delivery
The procedure for twins differs significantly from that of a single baby due to the heightened need for readiness and intervention. A twin vaginal delivery is nearly always performed within an operating room environment, even if the goal is a non-surgical birth. This location ensures that medical staff can perform an immediate emergency Cesarean section for the second twin if complications arise after the first baby is born.
Throughout the labor process, both twins are monitored continuously using electronic fetal monitoring to track their heart rates and well-being. Once Twin A is born, the medical team immediately assesses the position and health of Twin B, often using an ultrasound. The interval between the delivery of the two babies is a time of intense focus, as it carries a risk of complications like placental abruption or umbilical cord prolapse.
While there is no rigid time limit, the median time for the second twin’s birth is around 30 minutes, though an optimal interval of 10 to 16 minutes is associated with favorable outcomes. If Twin B is not head-down or if its heart rate is concerning, the obstetrician may use specialized maneuvers to facilitate its delivery. These maneuvers include an internal podalic version, where the doctor manually turns Twin B inside the uterus to grasp the feet, followed by a breech extraction.
Scenarios Requiring a Planned Cesarean Delivery
A planned Cesarean delivery is required when certain medical conditions or fetal presentations are present, as attempting a vaginal delivery would significantly increase the risk to the mother or babies. The most common contraindication is the presentation of the first twin, Twin A, if it is not head-down but is instead in a breech (feet or bottom first) or transverse (sideways) position. In these cases, the risk of the head becoming trapped is too high to justify a vaginal attempt.
Certain placental conditions also necessitate a planned Cesarean, such as placenta previa, where the placenta completely or partially covers the mother’s cervix, blocking the exit. Specific types of twin pregnancies, such as monochorionic-monoamniotic (MoMo) twins, are routinely delivered via C-section due to the high likelihood of the babies’ umbilical cords becoming entangled during labor.
Furthermore, any condition that would contraindicate a vaginal delivery in a single pregnancy also applies to twins, including severe fetal growth restriction, certain maternal heart conditions, or severe preeclampsia. In the rare instance of conjoined twins, a Cesarean section is the only safe delivery method. When these factors are present, a planned Cesarean delivery is scheduled in advance to ensure the safest possible outcome.