How your twins’ fetal positions affect labor and delivery
win fetal presentation – also known as the position of your babies in the womb – dictates whether you’ll have a vaginal or c-section birth. Toward the end of pregnancy, most twins will move in the head-down position (vertex), but there’s a risk that the second twin will change position after the first twin is born. While there are options to change the second twin’s position, this can increase the risk of c-section and other health issues. Learn about the six possible twin fetal presentations: vertex-vertex, vertex-breech, breech-breech, vertex-transverse, breech-transverse, and transverse-transverse – and how they’ll impact your delivery and risks for complications.
What is fetal presentation and what does it mean for your twins?
As your due date approaches, you might be wondering how your twins are currently positioned in the womb, also known as the fetal presentation, and what that means for your delivery. Throughout your pregnancy, your twin babies will move in the uterus, but sometime during the third trimester – usually between 32 and 36 weeks – their fetal presentation changes as they prepare to go down the birth canal.
The good news is that at most twin births, both babies are head-down (vertex), which means you can have a vaginal delivery. In fact, nearly 40 percent of twins are delivered vaginally.
But if one baby has feet or bottom first (breech) or is sideways (transverse), your doctor might deliver the lower twin vaginally and then try to rotate the other twin so that they face head-down (also called external cephalic version or internal podalic version) and can be delivered vaginally. But if that doesn’t work, there’s still a chance that your doctor will be able to deliver the second twin feet first vaginally via breech extraction (delivering the breech baby feet or butt first through the vagina).
That said, a breech extraction depends on a variety of factors – including how experienced your doctor is in the procedure and how much the second twin weighs. Studies show that the higher rate of vaginal births among nonvertex second twins is associated with labor induction and more experienced doctors, suggesting that proper delivery planning may increase your chances of a vaginal birth.
That said, you shouldn’t totally rule out a Cesarean delivery with twins. If the first twin is breech or neither of the twins are head-down, then you’ll most likely have a Cesarean delivery.
Research also shows that twin babies who are born at less than 34 weeks and have moms with multiple children are associated with intrapartum presentation change (when the fetal presentation of the second twin changes from head-down to feet first after the delivery of the first twin) of the second twin. Women who have intrapartum presentation change are more likely to undergo a Cesarean delivery for their second twin.
Here’s a breakdown of the different fetal presentations for twin births and how they will affect your delivery.
. Head down, head down (vertex, vertex)
This fetal presentation is the most promising for a vaginal delivery because both twins are head-down. Twins can change positions, but if they’re head-down at 28 weeks, they’re likely to stay that way.
When delivering twins vaginally, there is a risk that the second twin will change position after the delivery of the first. Research shows that second twins change positions in 20 percent of planned vaginal deliveries. If this happens, your doctor may try to rotate the second twin so it faces head-down or consider a breech extraction. But if neither of these works or are an option, then a Cesarean delivery is likely.
In vertex-vertex pairs, the rate of Cesarean delivery for the second twin after a vaginal delivery of the first one is 16.9 percent.
Like all vaginal deliveries, there’s also a chance you’ll have an assisted birth, where forceps or a vacuum are needed to help deliver your twins.
. Head down, bottom down (vertex, breech)
When the first twin’s (the lower one) head is down, but the second twin isn’t, your doctor may attempt a vaginal delivery by changing the baby’s position or doing breech extraction, which isn’t possible if the second twin weighs much more than the first twin.
The rates of emergency C-section deliveries for the second twin after a vaginal delivery of the first twin are higher in second twins who have a very low birth weight. Small babies may not tolerate labor as well.
. Head down, sideways (vertex, transverse)
If one twin is lying sideways or diagonally (oblique), there’s a chance the baby may shift position as your labor progresses, or your doctor may try to turn the baby head-down via external cephalic version or internal podalic version (changing position in the uterus), which means you may be able to deliver both vaginally.
. Bottom down, bottom down (breech, breech)
When both twins are breech, a planned C-section is recommended because your doctor isn’t able to turn the fetuses. Studies also show that there are fewer negative neonatal outcomes for planned C-sections than planned vaginal births in breech babies.
As with any C-section, the risks for a planned one with twins include infection, loss of blood, blood clots, injury to the bowel or bladder, a weak uterine wall, placenta abnormalities in future pregnancies and fetal injury.
. Bottom down, sideways (breech, transverse)
When the twin lowest in your uterus is breech or transverse (which happens in 25 percent of cases), you’ll need to have a c-section.
. Sideways, sideways (transverse, transverse)
This fetal presentation is rare with less than 1 percent of cases. If both babies are lying horizontally, you’ll almost definitely have a C-section.