Surgical abortion pre-term risk
Women who have "surgical" abortions are more likely in the future to give birth to babies prematurely than women who have medically-induced terminations, a study suggests.
The research is published in the open access journal BMJ Open.
In addition, the research adds evidence to previous work showing that women who have induced abortions increase their risk of having a premature baby.
The work was based on a large study of more than 600,000 women from Scotland.
Although a consensus exists within medicine that abortions tend to lead to premature births during subsequent pregnancies, Prof Siladitya Bhattacharya from the University of Aberdeen and his colleagues investigated how differing methods of termination affected the future likelihood of premature births.
The researchers analysed anonymous records of Scottish women from 1981 to 2007 and found that abortions, in general, increased the risk of giving birth prematurely during future pregnancies by 37% in comparison to the risk for women who had never before been pregnant.
This was lower than the risk of premature birth following a miscarriage.
"Surgical" terminations were found to increase the risk of spontaneous pre-term births.
But women who underwent "medical" terminations, where pharmaceuticals are used to induce termination rather than a physical procedure, were not more likely to give birth prematurely than women who had never been pregnant before.
"The one reason that we hypothesised could be the cause, is that there's something about surgical abortion that has an impact on the cervix and makes it less resilient in a subsequent pregnancy and therefore makes it more likely that there will be a pre-term birth," Prof Bhattacharya told BBC News.
Although the study seems to imply that surgical abortions are more likely to induce pre-term births, Prof Bhattacharya said he was aware medical abortions could only be used up to a certain point during pregnancy, and that they required different resources than surgical abortions.
"Like many other interventions in medicine, it's about the evidence but its also about the interpretation, preference and availability of facilities," he said.
Surprisingly, the team found that whilst one abortion increased the chance of a pre-term birth, repeat procedures did not seem to incrementally boost the risk.
"This was interesting because there are other studies that have shown disagreement," Prof Bhattacharya said.
"A recent paper from Finland has found [that more abortions lead to a greater risk], but there are several aspects of that paper which are materially different from our work."
Over a quarter of induced abortions in Scotland in 2005 were repeat procedures, and over 70% of abortions are now medical.
Prof Bhattacharya was speaking at the British Science Festival which is being held at the University of Aberdeen.