Letter in response to Bhattachariya et al. August 2012
Re:Reproductive outcomes following abortion: A national register- based cohort study in Scotland. Bhattacharya S et al. BMJOpen August 2012
The authors of this study do not acknowledge that some hundreds of Scottish resident women come to England each year for abortions. As a consequence they are underestimating the risk of premature births post abortion.
The numbers are significant. In 2000 there were 345 women resident in Scotland reported in Abortion Statistics for England & Wales. And in 2005 there were 310 and 254 in 2010. Scotch resident women had 12604 abortion within Scotland in 2005 and 12785 in 2010. So this failure to count Scotch abortions in England is undercounting by 2.5% in 2005 and by 2% in 2010.
But that is not a full description of what the authors have missed. Scots women often come to England for late abortions which are more likely to incur the complications that lead to difficulties in subsequent pregnancies. In 2006 39% of abortions in England carried out on Scottish resident women were late abortions at 13 or more weeks gestational age of the foetus, compared to around 10% late abortions for resident women in England.
It seems impressive when the authors report Risk Ratios that are based on a large national linked study of this kind covering an entire population. But if the Scotch abortions that take place in England are counted, we can more reasonably assume that the risk ratios are wrong by around 5% and there is an understating of the risk of preterm births post abortion by a corresponding margin.
PAPRI: Pension and Population Research Institute
Conflict of Interest: