Miscarriage may affect women’s future pregnancies
Publication Date:21/12/2007
Introduction
A study suggests that women who've had a miscarriage or an abortion may be more likely to have a premature or underweight baby in future. But the study uses information from almost 50 years ago, when medical care was very different. So it's hard to know what it means for women today.
What do we know already?
There have been quite a lot of studies looking at whether having a miscarriage or an abortion can affect a woman's future pregnancies. But the studies have found different things. Some found women were more likely to have a premature baby (before 37 weeks), or a very small baby. Other studies found it made no difference.
Babies born too soon or who are underweight (less than 5.5lbs or 2.5kg) sometimes have serious health problems. So it's important to know what affects the risk of this happening.
What does the new study say?
The new study looked at old information, but analysed it in a new way. It found that women who had premature or underweight babies between 1959 and 1966 in the USA were much more likely to say they'd previously had a miscarriage or abortion.
The more miscarriages or abortions the women had, the higher the risk of premature or underweight babies. Miscarriages and abortions were counted together, so we don't know how many of each there were. This means we can't tell which was the most important.
It's important to keep the findings in perspective. Most of the women in the study (85 out of 100) had healthy babies, born weighing more than 5.5lbs, after 37 weeks.
Where does the study come from?
The study was carried out by researchers at Virginia Commonwealth University, in Virginia, USA. It was published in the Journal of Epidemiology and Community Health, which is owned by the British Medical Association.
How reliable are the findings?
There are some big problems with the study. The most obvious is that it uses information collected 41 to 47 years ago. Much has changed since then. Abortion was illegal in the US until 1973, so women who’d had an abortion in the 1950s or 1960s were less likely to tell researchers. Also, the medical care they had was not likely to be very good. They might have had complications from the operation, or from infections afterwards. So we can’t really compare these figures to what happens to women today.
However, it is a very big study, looking at more than 45,000 births. The researchers took account of lots of other things that might have caused premature births and low weight babies, including whether the mother smoked, had illnesses such as diabetes, and whether she’d attended all her antenatal visits. And the results were quite clear, even after accounting for all these things.
So we can say that these findings probably hold true for the time – US women in the 1950s and 1960s had a bigger risk of having a premature or underweight baby if they’d previously had a miscarriage or abortion. We just don’t know if these risks apply today.
What does this mean for me?
Because the figures are so old, it's difficult to know if they are relevant to women today. Healthcare has changed a lot since the 1960s. Women who had a miscarriage or abortion in the 1960s might have been treated differently today. In addition, antenatal care is better today, so problems like underweight babies may be picked up earlier with ultrasound scans.
If you've had an abortion or miscarriage, and you're of childbearing age today, we don't know whether you have a bigger risk of problems with any future pregnancy. This study can't answer that question.
What should I do now?
If you are pregnant, and you've have had a miscarriage or an abortion in the past, you may find this story worrying. But because of problems with the study, we're not sure if it's relevant to women today. The important thing is for you to enjoy a healthy pregnancy and look forward to the birth of your baby.
It's a good idea to let your midwife or doctor know that you've had these problems in the past. That way they can take good care of you, and be alert for any difficulties with your current pregnancy.
From:
Brown JS Jr, Adera T, Masho SW. Previous abortion and the risk of low birth weight and preterm births. Journal of Epidemiology and Community Health. 2008;62:16-22.
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© BMJ Publishing Group Limited ("BMJ Group") 2007. All rights reserved
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