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An international study has found that the majority of women are not getting the essential nutrients needed to support a healthy pregnancy and researchers warn the situation could worsen as more people adopt vegetarian or vegan diets.

The research, which analysed the vitamin status of 1,729 women in the UK, Singapore and New Zealand, focused on key nutrients typically found in meat and dairy, including vitamins D, B12, B6, folic acid and riboflavin.

These nutrients are critical during pregnancy:

• Folic acid and vitamin B12 help reduce the risk of neural tube defects such as spina bifida
• Vitamin D supports the immune system and supports healthy bones, teeth, and muscle function
• Riboflavin plays a role in the development of bones, muscles, and the nervous system in the growing baby

Over 90% of the women studied had low or marginal levels of one or more of these vitamins. Many also showed signs of vitamin B6 deficiency by late pregnancy. Professor Keith Godfrey, lead author and professor of epidemiology at the University of Southampton, commented:

“The push to reduce our dependence on meat and dairy to achieve net-zero carbon emissions is likely to further deplete expecting mothers of vital nutrients, which could have lasting effects on unborn children.”

The Study: Supplementation and Results

Participants were divided into two groups:

• An intervention group of 870 women
• A control group of 859 women

Both groups received a basic supplement containing:

• 400mcg folic acid
• 12mg iron
• 150mg calcium
• 150mcg iodine
• 720mcg beta-carotene

However, the control group was given a broader micronutrient formula, including:

• 1.8mg riboflavin
• 2.6mg vitamin B6
• 5.2mcg vitamin B12
• 10mcg vitamin D
• 10mg zinc
• Myo-inositol and probiotics

Blood samples were collected at four points: pre-conception, early pregnancy, late pregnancy, and six months postpartum. The results? Supplements that included a wider range of vitamins and minerals substantially reduced the prevalence of deficiencies both before and during pregnancy.

The researchers concluded that, in high-income countries, where diets are increasingly plant-based and potentially less nutrient-dense, micronutrient supplementation should be more actively considered as part of routine preconception and pregnancy care.

“The findings suggest a need to reappraise dietary recommendations for preconception and pregnancy, and to further explore the role of comprehensive multinutrient supplements,” they added.

NHS Guidance and Real-World Gaps

Current NHS guidance recommends that women trying to conceive take 400mcg folic acid daily from before pregnancy through to 12 weeks, to help reduce the risk of birth defects. A daily vitamin D supplement is also advised.

But this new study highlights a broader issue: even among women in high-income countries, widespread nutrient insufficiency is present before pregnancy even begins.

Prof Godfrey added:

“Our study shows that almost every woman trying to conceive had insufficient levels of one or more vitamin, and this figure is only going to get worse as the world moves towards plant-based diets.

People think nutrient deficiency is only an issue in low-income countries - but it’s clearly affecting the majority of women in wealthier nations too.”

The study was published in PLOS Medicine and led by researchers from the University of Southampton, with support from the NIHR Biomedical Research Centre, the University of Auckland, National University of Singapore, and Singapore’s Agency for Science, Research and Technology.