When and How to Deliver Twins: The Delivery Numbers Your Doctor Should Be Discussing With You
Twin delivery timing is not one decision. It is a different decision for every placental type, and it changes the moment something goes wrong.
Twin delivery planning involves two separate decisions that are often collapsed into one:
timing (what week) and
mode (vaginal or cesarean).
Both depend on many circumstances such as chorionicity, fetal position, whether complications have developed, and the experience of your delivery team. Patients are frequently told a delivery week without understanding why that number was chosen. This post gives you the numbers behind those decisions.
The Delivery Clock: Different Twins, Different Weeks
Every twin pregnancy has a gestational age beyond which the risk of continuing the pregnancy exceeds the risk of delivery. That threshold is different for each placental type, and it was not established by opinion. It was established by data showing when stillbirth risk begins to outweigh neonatal complications from early delivery.
A systematic review and meta-analysis of 32 studies covering 35,171 twin pregnancies found the following: in dichorionic twins, the risk of stillbirth from watchful waiting and the risk of neonatal death from delivery were balanced at 37 weeks. Delaying delivery by just one additional week, to 38 weeks, resulted in an additional 8.8 perinatal deaths per 1,000 pregnancies (1). That is not a theoretical risk. That is a measurable increase in death from waiting one week too long.
Here is what the evidence supports for uncomplicated twin pregnancies:
Dichorionic-diamniotic twins: Delivery at 37 to 38 weeks. ACOG recommends 38 weeks 0 days to 38 weeks 6 days. NICE and RCOG recommend from 37 weeks. The evidence favors not going past 38 weeks (1,2,3).
Monochorionic-diamniotic twins: Delivery at 36 to 37 weeks. The RCOG 2024 update recommends planned birth between 36 weeks 0 days and 36 weeks 6 days. ISUOG 2025 supports the same window. ACOG recommends 36 weeks 0 days to 37 weeks 6 days (2,3,4).
Monochorionic-monoamniotic twins: Delivery at 32 to 34 weeks by planned cesarean. Both ACOG and RCOG recommend this range. The reason is the persistent risk of cord entanglement and acute cord compression, which cannot be predicted by any antenatal test and which can cause sudden fetal death (2,4,5).
These are the dates for uncomplicated pregnancies. When complications develop, delivery moves earlier.
When Complications Change the Timeline
The delivery week listed above applies only when everything remains normal. Twins are prone to complications that singleton pregnancies either do not face or face at lower rates. When these complications appear, the delivery date moves forward, sometimes by weeks.
Preeclampsia and Hypertensive Disorders
Preeclampsia occurs more frequently in twin pregnancies than in singletons. When it develops, delivery timing follows the severity, not the twin schedule.
Gestational hypertension without severe features: delivery at 37 weeks (same as singleton management, which in twins may already be the planned delivery date for di-di twins). Preeclampsia without severe features: delivery at 37 weeks 0 days, or earlier if the clinical picture worsens. Preeclampsia with severe features: delivery at 34 weeks 0 days, or sooner if the mother or fetuses are unstable. HELLP syndrome or eclampsia: delivery after maternal stabilization regardless of gestational age (6).
In a twin pregnancy, preeclampsia can mean the planned delivery date becomes irrelevant. A mono-di twin pregnancy that was expected to deliver at 36 weeks may need delivery at 32 weeks because of worsening maternal blood pressures, rising liver enzymes, or dropping platelet counts. This is not a failure of the plan. It is the plan responding to maternal physiology.
Fetal Growth Restriction
Growth restriction in twins must be evaluated by chorionicity because the implications differ.
In dichorionic twins, fetal growth restriction behaves like singleton growth restriction. The fetuses have separate circulations, so one twin’s growth problem does not directly affect the other. Delivery depends on the severity: if the umbilical artery Doppler shows positive end-diastolic flow, close surveillance continues and delivery is considered at 37 weeks. If there is absent end-diastolic flow, delivery at 34 weeks. If there is reversed end-diastolic flow, delivery at 32 weeks or earlier depending on other findings (3,4,7).
In monochorionic twins, growth restriction is a different and more dangerous entity called selective fetal growth restriction (sFGR). Because the twins share a circulation through placental vascular connections, growth restriction in one twin can affect both. The RCOG classifies sFGR in monochorionic twins by umbilical artery Doppler pattern (4):
Type I sFGR (positive end-diastolic flow in the umbilical artery of the smaller twin): Generally favorable prognosis. Planned birth between 34 to 36 weeks if growth velocity is satisfactory and Dopplers remain normal. Type II sFGR (persistent absent or reversed end-diastolic flow): High risk of sudden deterioration and co-twin injury. Referral to a fetal medicine center for possible laser ablation or cord occlusion. Delivery often at 32 weeks or earlier. Type III sFGR (intermittent absent or reversed end-diastolic flow): Unpredictable. Requires close surveillance and individualized timing.
The key difference from singleton FGR is that in monochorionic twins, if one twin dies from growth restriction, the surviving twin is at risk of acute brain injury or death because blood can shift rapidly through the placental connections. That risk does not exist in dichorionic twins.
Twin-to-Twin Transfusion Syndrome (TTTS)
TTTS that requires laser treatment changes the delivery timeline based on what happens after the procedure. If laser treatment is successful and the pregnancy stabilizes, delivery is typically planned at 34 to 36 weeks. If complications develop after laser (recurrent TTTS, TAPS, preterm rupture of membranes), delivery may be needed earlier. If TTTS is diagnosed too late for laser (after 26 weeks at many centers), delivery timing depends on the severity and response to other interventions such as amnioreduction (8).
TTTS that is detected but remains at stage I (fluid discordance only) may be managed expectantly with very close surveillance, as approximately one-third of stage I cases resolve, one-third remain stable, and one-third progress (8).
Growth Discordance
Growth discordance, defined as a 25% or greater difference in estimated fetal weight between the twins, is a separate risk factor from growth restriction. One twin may be above the 10th percentile while the other is significantly larger. Even without one twin being technically “growth restricted,” a 25% or greater discordance independently increases the risk of adverse outcomes and typically moves delivery earlier, to 36 to 37 weeks for dichorionic twins and 34 to 36 weeks for monochorionic twins (3,4).
