Women who have an abortion may run an increased risk of subsequently giving birth to premature or low-weight babies, according to a study that will further fuel the abortion debate.
The review of a large amount of research, carried out in Canada, is likely to be seized on by the anti-abortion lobby as evidence that termination is damaging to future babies. However, the authors say there could be a number of reasons for their findings, of which the most likely is physical damage to the cervix caused by older methods of abortion.
The study found that women who had an abortion in the first or second trimester had a 35% increased risk of a low birth weight baby and a 36% raised risk of a pre-term baby in later pregnancies.
Dr Prakesh Shah, author of the review, published today in BJOG: An International Journal of Obstetrics and Gynaecology, said there was a need for better methods of terminating pregnancy and women needed better information. "When a woman comes for induced termination of pregnancy, she should be counselled about that risk. At least she will be able to make an informed choice," he said.
Shah, of the department of paediatrics at Mount Sinai hospital in Toronto, said he was anxious that the conclusions of the review should not be misrepresented by anti-abortion groups.
"I think it should not be used as a way of saying, this is bad and we should not be doing this kind of thing. There is an association which we should be aware of, and we should let mothers be aware. I don't want unintended pregnancies to increase."
The Royal College of Obstetricians and Gynaecologists said it wished to "underline the importance of support for women's choices, and the need for sensitivity in counselling women about termination of pregnancy in line with current research evidence. Abortion remains an essential part of women's healthcare services."
The college called for further studies, but added that it would take the new research into consideration when updating its abortion guidelines.
The Toronto group has been looking into all the reasons why babies are born premature and underweight. The researchers pulled together evidence from 37 studies around the world, carried out between 1965 and 2001, to find out whether previous abortion might be one of the factors.
They discovered that in women who had undergone more than one abortion, there was a 72% increased risk for low birth weight and 93% for prematurity. There was no increased risk that the baby would be small for gestational age.
Shah said the process of termination could cause some damage to the cervix, which has to be dilated, or to the womb. "Newer methods are probably safer. However, we could not find any data on which to base that assumption because they have not been studied," he said. In particular, drug-induced abortion, or using a drug to soften and ripen the cervix before mechanical dilation, may prevent damage.
Many women with a history of abortion tend to be unmarried, young and from socio-economically disadvantaged groups, the paper notes, but the researchers believe they have allowed for this in their calculations.
Professor Philip Steer, editor in chief of BJOG, said it was important that the study was properly interpreted. "The most important message is not that this should be used in any way to prevent women having a termination of pregnancy.
"The effect has to be balanced against the serious effects of forcing women to continue with unwanted pregnancies," he said. "Any medical procedure is likely to have side-effects."