A diet rich in fruit, vegetables, seafood, dairy, eggs, and grain may be associated with lower miscarriage odds, according to a new study from the University of Birmingham.
Estimates suggest around 1 in 6 pregnancies end in miscarriage. Almost half of early pregnancy losses are unexplained, though there is some evidence of lifestyle influences both before conception and in the early stages of pregnancy.
"The evidence on the association between diet and miscarriage risk is scant and conflicting," said researchers from the Tommy's National Centre for Miscarriage Research at the University of Birmingham.
The study, published in Fertility and Sterility, performed a systematic review and meta-analysis of 20 observational studies including a total of 64,776 healthy women of reproductive age who had had at least one pregnancy outcome. From 11 cohort and nine case-control studies, they found six with suitable data for meta-analysis, covering 13,183 women.
Risk Reduced With Healthy Foods, Increased With Processed Foods
The study revealed no evidence of an association between adherence to pre-defined dietary patterns such as the Mediterranean diet or 'fertility diet' and risk of miscarriage (defined as the loss of pregnancy before viability). However, when they looked at specific food groups, they found that high compared with low consumption of fruit was associated with a 61% reduction in miscarriage risk, while equivalent reductions were 41% for vegetable intake, 37% for dairy products, 33% for grains, and 19% for seafood and eggs.
These are foods typically found in 'healthy' well-balanced diets, the researchers noted, consistent with previous evidence showing that such diets, which are rich in vitamins and minerals, are important during pregnancy.
Their analysis showed that diets with a high antioxidant index score and low in pro-inflammatory foods were associated with reduced miscarriage risk (OR 0.43, 95% CI 0.20 to 0.91), whereas diets with a high content of processed foods were associated with an almost doubled risk (OR 1.97, 95% CI 1.36 to 3.34). Findings were unclear for meat, red meat, white meat, fat and oil, and sugar substitutes.
Positive Lifestyle Choices 'Make a Significant Difference'
Lead researcher Dr Yealin Chung said: "Nearly 50% of early pregnancy losses remain unexplained, and in the absence of a cause, parents often turn to their healthcare providers for guidance on the best ways to be as healthy as possible and reduce the risk of future miscarriages."
He added: "By knowing that positive lifestyle choices can make a significant difference in reducing the risk of miscarriage, couples can feel empowered to take charge of their health and the health of their baby."
Tommy's midwife Juliette Ward agreed that dietary advice was "one of the most-discussed subjects" and that many women wanted to know how to be as healthy as possible in pregnancy, but there had been "a lack of clear evidence on the links between diet choices and miscarriage".
The review's findings suggest evidence-based guidelines on dietary advice "could make a real impact in helping people reduce their risk".
The team concluded: "An overall dietary exposure that is high in quality with healthy nutrient sources, low in pro-inflammatory factors or unhealthy food groups such as highly refined, processed meat, or sugar substitutes, may be associated with a reduction in miscarriage risk."
While further interventional studies are required accurately to assess the effectiveness of peri-conception dietary modifications on miscarriage risk, "women who wish to reduce their risk of pregnancy loss should be encouraged to make healthy food choices".
Asked to comment by Medscape News UK, Ruth Bender Atik, national director of the Miscarriage Association, said: "Diet, what to eat and what to avoid in pregnancy is an issue that often concerns women and their partners, both before pregnancy and perhaps especially if they suffer a miscarriage.
"This useful review and meta-analysis reinforces much of the existing guidance on diet in pregnancy, along with some less-discussed findings. Its measured tone may make this information both more accessible and more acceptable amongst those who might already experience guilt and self-blame after pregnancy loss."
The study was funded by Tommy's, a pregnancy charity that funds research into pregnancy complications, including miscarriage and stillbirth.