Stillborn babies are four times more likely in women undergoing IVF than through natural pregnancies, a Danish study has suggested.
The study suggests the fertility treatments are responsible for the increased risk, although the chance of stillbirth was still very low, said researchers from Aarhus University Hospital.
Stillbirth was also four times more likely where the sperm is injected directly into the egg in a process called intracytoplasmic sperm injection (ICSI).
The effect of IVF and ICSI was compared with that on women who got pregnant naturally or had other fertility treatments. The results of more than 20,000 pregnancies of single babies were analysed, with a clear increased risk for stillbirth after IVF and ICSI. However, the authors said more research was needed into the exact reasons.
The research, published in the journal Human Reproduction, looked at Danish pregnancies from 1989 to 2006. A recent, larger study in Sweden found no link between IVF and increased risk of stillbirth.
According to Office for National Statistics data, there were 3,617 stillbirths in England and Wales in 2008, or 5.1 per 1,000 births.