Thursday December 1 2016
Miscarriages are more common than many people realise
"Women who suffer a miscarriage should try for a baby again within six months, a major study has found," the Daily Mail reports.
Current guidance from the World Health Organization recommends couples wait at least six months before trying to conceive again after a miscarriage. But the researchers decided to investigate the validity of this recommendation as it was based on a single study from women in the developing world.
The researchers looked at information taken from around 1 million women from 11 different countries around the world. It found no more adverse outcomes for women who get pregnant less than six months after a miscarriage compared to those who wait. Moreover, a reduced risk of miscarriage and preterm birth was found for these women.
So this study suggests these guidelines should be reviewed and that couples be advised that delaying pregnancy doesn't necessarily improve outcomes.
If you have had a miscarriage, you should avoid having sex until all of your miscarriage symptoms have gone. Your periods should return within four to six weeks of your miscarriage, although it may take several months to settle into a regular cycle.
Not every woman will feel physically and/or emotionally ready to try for another pregnancy. Charities such as the Miscarriage Association can provide advice and support about trying for another pregnancy.
Where did the story come from?
The study was carried out by researchers from the University of Malta and the University of Aberdeen and did not receive any funding.
The study was published in the peer-reviewed medical journal Human Reproduction Update and the authors declare no conflict of interest.
The media generally reported the story accurately, acknowledging that women are more likely to have a successful pregnancy if they conceive sooner after a miscarriage, rather than waiting.
The Daily Mail suggests that women who have a miscarriage "should try for a baby again within six months". However not all women will feel emotionally ready to try again for a baby so soon.
What kind of research was this?
This was a systematic review and meta-analysis aiming to see if becoming pregnant less than six months after miscarriage is associated with adverse outcomes in the next pregnancy, compared with getting pregnant more than six months later.
Meta-analyses are a useful way of summarising many studies looking at the same outcomes, in this case adverse pregnancy outcomes.
However, this type of study will only ever be as good as the individual studies included, and weaknesses from these studies will be brought into the analyses.
The studies included were 13 cohort studies and three randomised controlled trials, from 11 different countries.
Cohort studies are a good way of looking at a link between two factors, but cannot prove that one – falling pregnant before six months – causes another – future pregnancy outcomes.
What did the research involve?
Researchers compared the results of 1,043,840 women from 16 trials. They then pooled the results of 10 similar trials, involving 977,972 women. They compared the difference in pregnancy-related outcomes between women who fell pregnant less than six months after having a miscarriage, and those who fell pregnant more than six months after miscarriage.
They looked at outcomes, including:
The results were analysed and the risk of each outcome for the two groups of women (less than six months to pregnancy or more than six months to pregnancy) was calculated.
What were the basic results?
Results showed that in women with less than six months between miscarriage and pregnancy compared to those with a six months or more interval, there was a:
- decreased risk of further miscarriage of 18% (risk ratio (RR) 0.82, confidence interval (CI) 0.78 to 0.86)
- decreased risk of preterm delivery of 21% (RR 0.79, 95% CI 0.75 to 0.83)
There was no significant difference between women with less than six months or more than six months between miscarriage and pregnancy for still birth, low birthweight or pre-eclampsia.
How did the researchers interpret the results?
The researchers concluded: "The results of this systematic review and meta-analyses show that an IPI [inter-pregnancy interval] of less than six months is associated with no increase in the risks of adverse outcomes in the pregnancy following miscarriage compared to delaying pregnancy for at least six months."
In fact, there is some evidence to suggest that chances of having a live birth in the subsequent pregnancy are increased with an IPI of less than six months.
They go on to add: "there is now ample evidence to suggest that delaying a pregnancy following a miscarriage is not beneficial and unless there are specific reasons for delay couples should be advised to try for another pregnancy as soon as they feel ready."
This study shows that getting pregnant sooner after a miscarriage results in no more adverse outcomes compared to waiting for more than six months.
In addition, there appear to be better outcomes in terms of a lower risk of further miscarriage and possibly preterm birth. It should be pointed out that for preterm birth the result only reached statistical significance when one of the relevant studies was excluded, which limits our confidence in this result.
This study has strengths as it included a large number of women from many different countries. However, it also has limitations:
- The way data was collected from the original studies varied. Some used mother's recall while others gained information from databases – therefore the quality of data varied.
- Studies had different definitions of miscarriage. While some included only spontaneous abortion (miscarriage), others did not distinguish between spontaneous and induced abortion.
However, there are a number of confounding factors that influence pregnancy outcomes, including:
- maternal age
- social class
- previous obstetric history
Other than maternal age, the included studies varied in addressing these potential confounding variables, which could have led to an over- or under-estimation of results.
Miscarriages are fairly common. Among women who know they're pregnant, it's estimated one in six of these pregnancies will end in miscarriage.
Recurrent miscarriages (losing three or more pregnancies in a row) are far less common, affecting only around 1 in a 100 women.
If you do want to get pregnant again, you may want to discuss it with your GP or hospital care team. Make sure you are feeling physically and emotionally well before trying for another pregnancy.
The Miscarriage Association provides more advice about trying for another pregnancy.