The delivery window
Unlike singleton pregnancies, where the due date hovers around 40 weeks, twin pregnancies follow a shorter timeline. The American College of Obstetricians and Gynecologists (ACOG) recommends delivery at 38 weeks for dichorionic-diamniotic (di/di) twins and 36 weeks for monochorionic-diamniotic (mo/di) twins. Monochorionic-monoamniotic (mo/mo) twins are typically delivered between 32 and 34 weeks due to cord entanglement risk.
These timelines are based on large studies demonstrating that the risk of stillbirth increases beyond these gestational ages in twin pregnancies, while the benefits of further fetal maturation plateau. The NICE guidelines in the UK and the SMFM (Society for Maternal-Fetal Medicine) in the US agree on these windows.
About 60 percent of twins are born before 37 weeks, with the average gestational age at delivery being 35 to 36 weeks. Preterm birth is common with twins, which is why your care team plans for NICU readiness even when everything is progressing well.
Vaginal birth with twins: when and how
Vaginal birth is possible and often encouraged for twins when conditions are favorable. The landmark Twin Birth Study (published in the New England Journal of Medicine in 2013) followed over 2,800 twin pregnancies and found that planned vaginal delivery, when Twin A was head-down, was as safe as planned cesarean for babies born between 32 and 38 weeks.
The primary factor determining vaginal delivery eligibility is the position of Twin A (the baby closest to the birth canal):
Both babies head-down (vertex/vertex)
This is the most straightforward scenario, occurring in roughly 40 percent of twin pregnancies at the time of delivery. Both babies are positioned for a vaginal birth, and delivery proceeds similarly to a singleton vaginal birth, with Twin B born shortly after Twin A.
Twin A head-down, Twin B breech or transverse (vertex/breech or vertex/transverse)
This occurs in approximately 35 to 40 percent of cases. If your provider is experienced with breech extraction (a specific technique for delivering the second twin), vaginal delivery is still an option. After Twin A is born, the provider may perform an external cephalic version (turning the baby from outside) or a breech extraction for Twin B. The Twin Birth Study confirmed the safety of this approach in experienced hands.
Twin A breech
If the presenting twin is breech (feet or buttocks first), most providers will recommend a cesarean delivery. The rationale is that breech first-twin delivery carries higher risk, and there is no comparable evidence for its safety like there is for second-twin breech extraction.
What twin vaginal delivery looks like
A twin vaginal delivery happens in the operating room (OR), even though it is a vaginal birth. This is standard practice because approximately 4 to 8 percent of planned vaginal twin deliveries require an emergency cesarean for Twin B after Twin A is born vaginally. Having the OR ready eliminates dangerous delays.
Here is what to expect:
- Labor progresses as with a singleton. Contractions, cervical dilation, and pushing for Twin A follow the same stages.
- Twin A is born. Cord is clamped and cut, and baby is assessed.
- A brief interval follows. The time between Twin A and Twin B's birth varies from a few minutes to 30 minutes or more. Your provider will use ultrasound to confirm Twin B's position after Twin A is delivered.
- Twin B is born. If head-down, pushing continues. If breech, your provider may perform a breech extraction. If transverse, they may attempt external version or proceed with extraction.
- Placentas are delivered. One or two placentas, depending on your twin type.
The interval between babies is something many twin parents wonder about. Research suggests that intervals under 30 minutes are associated with the best outcomes for Twin B, though healthy babies are born with longer intervals too. Your care team will monitor Twin B's heart rate continuously during this window.
Cesarean delivery for twins
About 75 percent of twin births in the United States are delivered by cesarean section. This rate is higher than the evidence suggests is medically necessary, largely because many hospitals and providers lack experience with vaginal twin delivery. If vaginal birth is important to you, seek out a provider and hospital where twin vaginal deliveries are performed regularly.
Cesarean delivery is recommended when:
- Twin A is breech
- Mo/mo twins (due to cord entanglement risk during labor)
- Significant size discordance between twins (typically greater than 20 percent estimated weight difference)
- Placenta previa covering the cervix
- Prior classical (vertical) uterine incision
- Maternal or fetal conditions that make labor unsafe
A planned cesarean for twins is similar to a singleton cesarean. Twin A is delivered first through the uterine incision, followed almost immediately by Twin B. The entire surgical procedure typically takes 45 to 60 minutes, with the babies born within the first 10 to 15 minutes.
Twin A and Twin B: what the labels mean
Twin A is simply the baby closest to the cervix at the time of delivery. Twin B is above or beside Twin A. These designations are determined by position, and they can shift during pregnancy as babies move. The labels do not indicate which baby is "older" in any meaningful way; they are clinical identifiers for delivery planning.
After birth, the baby born first is typically designated as the firstborn twin, regardless of whether they were Twin A or Twin B during pregnancy. In vaginal deliveries, Twin A is almost always born first. In cesarean deliveries, the surgeon delivers the most accessible baby first, which is usually (but not always) the baby closest to the incision.
NICU: planning for probability
Even in uncomplicated twin pregnancies, NICU time is common. Roughly 40 to 60 percent of twins spend time in the NICU, compared to about 8 to 10 percent of singletons. Most NICU stays for twins are brief (a few days to two weeks) and relate to feeding support, temperature regulation, or observation of breathing patterns. Babies born before 36 weeks are more likely to need NICU support.
A few things to do in advance:
- Tour the NICU at your delivery hospital. Familiarity reduces anxiety enormously if your babies end up there.
- Ask about the hospital's NICU level. Level III NICUs provide the most comprehensive care for premature and complex newborns. If your hospital has a Level II, understand the transfer protocols in case your babies need more support.
- Discuss skin-to-skin in the NICU. Most modern NICUs encourage kangaroo care (skin-to-skin contact) as early as the babies are stable. It promotes bonding, temperature regulation, and breastfeeding.
Writing a twin birth plan
A birth plan for twins should be flexible because twin delivery involves more variables. Consider including:
- Your preference for vaginal birth if conditions allow
- Delayed cord clamping (if feasible; your provider will assess per baby)
- Skin-to-skin preferences for both babies
- Who will accompany you in the OR
- Feeding preferences for the first hours
- Photography or recording requests
- Whether you want to hold both babies simultaneously after delivery
Communicate your preferences clearly, but hold them loosely. Twin births can shift quickly, and a supportive care team will honor your wishes as closely as the clinical situation allows.
Find your birth team through Baaby
The experience of your care team with twin deliveries directly impacts your birth options and outcomes. Baaby's provider directory can help you find OB-GYNs who routinely deliver twins vaginally, as well as doulas experienced in supporting multiple births. A doula familiar with twin delivery can be an invaluable advocate in the OR, helping you stay grounded and informed as events unfold.