In vitro fertilization linked with increased risk of spontaneous preterm birth

A new analysis of published studies found an approximate 80% increased risk of spontaneous preterm birth (both before 37 and 34 weeks of gestation) when women become pregnant via in vitro fertilization (IVF) compared with through spontaneous conception.

A new analysis of published studies found an approximate 80% increased risk of spontaneous preterm birth (both before 37 and 34 weeks) when women become pregnant via in vitro fertilization (IVF) than through spontaneous conception. The systematic review and meta-analysis published in Ultrasound in Obstetrics and Gynecology included 15 studies with approximately 62 000 patients and about 3800 preterm birth events.

"Placental development may play a key role in the pathogenesis of spontaneous preterm birth in IVF pregnancies. We recommend ultrasound cervical screening in this high-risk group in order to apply timely preventive strategies” said lead author Dr Paolo Cavoretto, of the IRCCS San Raffaele Hospital, in Milan, Italy. “Future research reporting pregnancy outcomes should always emphasize etiological differentiation of preterm birth.”

ISUOG Board member Dr Nick Raine-Fenning comments:

"This is the first study to see whether the reported increased risk of preterm birth in women conceiving after IVF treatment was due to doctors intervening or a true increase in spontaneous premature labour. The study suggests the latter, with women conceiving after IVF appearing to be twice as likely to go into labour before 37 weeks than those conceiving naturally (10.1% vs 5.5%). Furthermore, they are also more likely to deliver their baby before 34 weeks (3.6% vs 2.1%), which puts even more strain on the newborn.

The reason for this is unknown, but many women who need IVF to conceive have other risk factors for preterm birth such as fibroids and uterine anomalies. More work is required to understand the underlying mechanisms and confirm the findings, but for now, women who conceive after IVF treatment should be considered at higher risk of preterm birth and managed accordingly. This may mean more frequent visits and serial ultrasound scans to check the length of the cervix, but at the very least these women should be aware of the risk and present to labour ward promptly if they have any signs or symptoms of labour which can be very subtle at this time."