Falling pregnant six months after an initial miscarriage offers women the best chance of having a healthy second pregnancy, according to research published in the British Medical Journal.
Though miscarriages are common, with one in five pregnancies estimated to end this way, the question of how long a couple should wait before trying for another pregnancy, remains controversial.
Current World Health Organisation guidelines recommend that women should wait at least six months after a pregnancy loss before trying again, but researchers from the University of Aberdeen and Aberdeen Maternity Hospital feel that this advice needs review.
Sohinee Bhattacharya and her team examined health records of over 30,000 women who attended Scottish hospitals between the years of 1981-2000. Their findings suggest that women who conceived within six months of an initial miscarriage were less likely to have another miscarriage than those who became pregnant between six and twelve months later. Pregnancies occurring within six months of the initial miscarriage were also less likely to result in complications such as ectopic pregnancies (pregnancies outside the womb), premature birth and low birth weight, and birth by caesarean section. In contrast, the researchers found that outcomes were worst for pregnancies which occurred over 2 years after the initial miscarriage.
The majority of other studies on this subject however, which have taken place in the developing world, suggest that women should wait at least six months prior to conceiving. The authors emphasise that this study focused on a Scottish population and that the results may not be applicable to other populations.
The study has other limitations - a number of factors such as smoking and maternal weight can also affect the outcome of pregnancies, but were not fully accounted for in the research, often due to a lack of data. It is also difficult to ascertain whether, in the group of women who fell pregnant more than two years after the initial miscarriage, it actually took longer for pregnancy to occur because of unidentified underlying problems. It is possible that such underlying problems were responsible for the greater rate of complications this group faced.
Sohinee Bhattacharya acknowledges this as a weakness in the study: "We can't be sure that those women who conceived later did not have any underlying pathology which was associated both with reduced fertility and subsequent pregnancy complications".
She adds, "It appears from our report, that the largest group of women had an interpregnancy interval of less than 6 months, perhaps adding strength to the argument of delayed conception following miscarriage being involuntary".
The authors also caution that there are certain circumstances - such as when an infection is present - that delaying pregnancy may be the best option.
Despite the limitations, the findings of this study of over 30,000 pregnancies, suggest that more research is needed to answer this question, which billions of women must face.