A treatment that prevents premature births in single pregnancies may be not work for women expecting more than one child, scientists at University of Edinburgh have found.
The study suggests an underlying difference between the way in which premature births occur in women with single and multiple pregnancies.
According to researchers, the findings could help inform improvements in treatment to prevent premature births in women expecting more than one child and help researchers understand how the process of premature labour may be different.
The researchers studied nearly 500 women. Half of the women were given progesterone gel - a hormone which helps protect the lining of the womb - while the other half were given a dummy version.
The treatment has been shown to reduce early births in women expecting one child considered at high risk of early labour, including those who had previously given birth prematurely.
However, researchers found that contrary to singleton pregnancies, the hormone gel did not reduce rates of premature births.
"While the study looked at twins, it suggests that the biological process of premature births in women with multiple births is different for that than in women expecting one child," Professor Jane Norman, director of the Tommy's Centre for Maternal and Fetal Health Research at the University of Edinburgh, said.
"Understanding the differences between what happens in premature births in singleton and multiple pregnancies can help us improve treatments and also address the higher incidence of premature labour in multiple pregnancies," Norman added.
The study has been published in the The Lancet.