In uncomplicated twin pregnancies, delivery should be considered at 37 weeks of gestation in order to minimize risk of stillbirths and newborn deaths. Where there is only one placenta, delivery should be considered at 36 weeks.
So recommends a large international study published in the BMJ that also concludes there is no clear evidence to support routine delivery before 36 weeks of gestation.
The findings give women expecting twins and the health professionals assisting them crucial information to help them plan for delivery.
Compared with singleton pregnancies, the risk of stillbirth and newborn deaths is higher in twin pregnancies. In an effort to minimize such risks, uncomplicated twin pregnancies are often delivered early.
However, there is little scientific evidence on what the optimal gestational age for delivering twins might be.
Existing recommendations vary, and they range from timing delivery at 34-37 weeks of gestation for twins that share the same placenta (monochorionic twin pregnancies), and 37-39 weeks for twins with two placentas (dichorionic twin pregnancies).
To address this shortfall, the international team reviewed 32 studies on twin pregnancies that were published in the last 10 years and carried out a pooled analysis of their data.
Altogether, the pooled data covered 35,171 twin pregnancies (29,685 dichorionic and 5,486 monochorionic).
The team only included studies on uncomplicated twin pregnancies that reported rates of stillbirth and newborn deaths (up to 28 days after birth) at various gestational ages after 34 weeks, and they also took into account study design and quality to minimize bias.
Their analysis focused on the balance between the risk of stillbirths from “watchful waiting” management of pregnancies and the risk of newborn death from deliveries after 34 weeks.
The results showed that in the case of dichorionic pregnancies, the risks between stillbirths and newborn deaths were balanced until 37 weeks of gestation. However, if delivery was just 1 week later – at 38 weeks of gestation – there were an extra 8.8 deaths per 1,000 due to more stillbirths.
For monochorionic pregnancies, this pattern (of risk of stillbirths exceeding newborn deaths) began after 36 weeks of gestation, but the researchers note more data is needed before there can be a clear recommendation on the optimal delivery time for monochorionic pregnancies.
The researchers suggest the actual risk of stillbirths in pregnancies that are near term might be higher than reported estimates suggest because of “the policy of planned delivery in twin pregnancies.”
However, they point out their findings offer “comprehensive estimates comparing risks of stillbirth and neonatal mortality at various gestational ages, which is required for the planning of delivery in uncomplicated twin pregnancies.”
The researchers say the information will help all efforts to reduce stillbirths and unexpected complications in babies born near term.
In the United States in 2014, there were 3,988,076 births, including 135,336 twin births, which works out at 33.9 twin births per 1,000 live births.
“To minimise perinatal deaths, in uncomplicated dichorionic twin pregnancies delivery should be considered at 37 weeks’ gestation; in monochorionic pregnancies delivery should be considered at 36 weeks.”
Fiona Cheong-See et al.