Twins should be delivered when an expectant mother is 37 weeks pregnant to reduce the risk of the babies dying, experts have said.

The recommendation comes from researchers who examined data on more than 35,000 twin pregnancies to determine when the best time for delivery should be.

The study, published in The BMJ, found that dichorionic pregnancies - twins who have individual placentas - should be delivered at 37 weeks, as delay by just a week led to an additional 8.8 deaths per 1,000.

Twins or triplets hold a higher risk of still birth or neonatal death. Mothers expecting multiple babies are often told their babies must be delivered early in a bid to reduce the risk.

Keith Reed, chief executive of the Twins and Multiple Births Association (Tamba), said: "A study of this size and with these significant findings has never been published in the UK before.

"The risk of stillbirth is higher in twin pregnancies than in singleton pregnancies, so any new information which could save the lives of more babies in multiple pregnancies is obviously an exciting step forward."

Mark Kilby, professor of foetal medicine and spokesman for the Royal College of Obstetricians and Gynaecologists, said: "Although multiple births account for just 3% of all births in the UK, they made up just under 10% of all stillbirths in England, Wales and Scotland in 2014.

"With any twin pregnancy, healthcare professionals should provide closer surveillance in order to ensure early diagnosis and treatment of possible complications. In addition, the risks and benefits of different delivery options and timings should be discussed so a woman can make informed decisions about her birth plan where possible."