Study identifies twin pregnancy risks

TWINS WITH separate placentas have a lower perinatal mortality rate than babies born in single pregnancies, a new study carried out in Ireland has found.

The all-Ireland study of twin pregnancies also found if the weight difference between a baby and its twin is greater than 18 per cent, there is an increased risk of health complications for both.

Led by Perinatal Ireland and the Royal College of Surgeons in Ireland, the study followed the pregnancies and deliveries of 1,001 women who were carrying twins in eight maternity centres in Ireland between 2007 and 2009.

Mothers had ultrasound scans every two weeks and were closely monitored throughout their pregnancies.

The study found a difference of 18 per cent or more in twin birth weights was associated with an increased risk of foetal or neonatal death, bowel complications, breathing difficulties, infection and admission to the neonatal intensive care unit.

Twins who shared a single placenta were found to be at the highest risk, while the larger twin was at equal risk with the smaller co-twin.

But the twins who had separate placentas, known as dichorionic twins, fared best. Their mortality rate was half that of babies born in single pregnancies.

In singletons in Ireland, the perinatal mortality rate is eight per 1,000, while the dichorionic twins in the study had a rate of half that.

Dr Fionnuala Breathnach, lead researcher and consultant obstetrician at the Rotunda Hospital, described the outcome as remarkable. She said the impressive results could be attributed to the “really high standards of obstetric care in Ireland”.

Participation in research was also found to be “a strategy to optimise outcomes” because of the level of attention given to each case, with all participants undergoing detailed examinations and ultrasound every two weeks.

She said the vast majority of women also delivered before their due date and that may have made a difference to mortality rates.

“Once you label a pregnancy as a high risk, they are the ones we tend not to lose,” she said.

“The toughest to identify is the high- risk baby carried by a low-risk mother.”

Two-thirds of the deliveries were by Caesarean section, but the study found where participants were carefully selected to try for normal delivery, there was a high level of success. It also found such “labour trials” did not place any additional risk on outcomes.

Dr Breathnach also said the identification of the threshold of weight difference, above which risk increases for both babies, was very important.

“It should trigger closer foetal monitoring and possibly early delivery,” she said.

The study will be published in the American Journal of Obstetrics and Gynaecologythis week.