Why morning sickness can actually be a good thing

It might be hard to believe when you are in the middle of a particularly bad bout of it, but researchers believe the dark cloud of morning sickness might have a silver lining.

Authors of the Canadian research, which analysed the results of 10 separate studies, say not only are women who suffer morning sickness less likely to miscarry in their first trimester, their babies are also less likely to have birth defects, be born prematurely or have low birthweight.

sick woman
sick woman Photo: Getty Images

All of the studies analysed showed a "protective effect" of nausea and vomiting during pregnancy, while one of them even found babies of queasy mums scored higher in IQ tests when aged between three and five years of age.

Researchers from The Hospital for Sick Children and the University of Toronto compiled data from the studies which were conducted between 1992 and 2012 and involved 850,000 pregnant women. Their results were published in the peer-reviewed journal Reproductive Toxicology included these findings:

 the risk of miscarriage was three times higher for women who did not suffer morning sickness during the first trimester

• around 6 per cent of mothers who suffered nausea during pregnancy had premature births, compared with 9.5 per cent of mothers who were not ill

• the analysis suggested the risk of birth defects was reduced by between 30 and 80 per cent for women who suffered morning sickness. 

The researchers suggested mothers aged 35 or older were more likely to benefit from these "protective effects" of nausea during pregnancy.

They also pointed out the findings might not be relevant for those who suffer hyperemesis gravidarum, which is severe and unrelenting vomiting, dehydration and sickness throughout pregnancy.

Lead author Gideon Koren said the positive outcomes might be a result of the hormones which cause morning sickness also creating favourable conditions for the pregnancy - but the report does point out that "this hypothesis has not been proven to date".

"Women with moderate to severe nausea and vomiting in pregnancy often experience major negative impact on their health and quality of life.

"Our analysis indicates that reassuring these women that their severe symptoms may confer favourable fetal outcome in their unborn babies, is logical. 

"While this may not be the case in women experiencing hyperemesis gravidarum, it does seem to be valid for the majority of pregnancies."

Don't have morning sickness? Don't worry

Despite the findings, don't stress if you're lucky enough to escape the clutches of morning sickness during pregnancy. As the British National Health Service points out on its website, "The results of this study may help to reassure women with nausea and vomiting in pregnancy that this may be a good sign – at least for some measures of a healthy, ongoing pregnancy.

"Overall, however ... the review does not prove that [morning sickness] will always indicate a healthy pregnancy.

"Importantly, it also does not prove the opposite – that a pregnancy without nausea and vomiting means a poorer outcome."