A pregnant woman's veganism affected her baby's weight the same way smoking did

In Western countries (and to some extent in Russia), more and more people are switching to plant-based diets, explaining their choice with concern for the environment and animal welfare. However, a new Danish study shows that women who follow a vegan diet during pregnancy may face certain problems.

The research paper, published in the journal Acta Obstetricia et Gynecologica Scandinavica, is based on data from the Danish National Pregnancy Cohort Study, which included more than 66,000 pregnant women between 1996 and 2002. Among them, one percent of the participants (or 666 people) identified themselves as fish/poultry vegetarians, 0.3 percent (183 people) were lacto/ovo-vegetarians, and just 0.03 percent (18 people) followed a vegan diet.

Using statistical analysis, the researchers examined the association between different types of plant-based diets during pregnancy and pregnancy outcomes. Compared to omnivores, mothers with vegan diets had a 240 gram lower average birth weight and a higher risk of pre-eclampsia, a pregnancy complication characterized by high blood pressure and protein in the urine. In addition, gestational length among them was 5.2 days longer. Combined with a lower average birth weight, this indicates a lower fetal growth rate.

Vegans also showed lower protein intake, which is thought to be a key factor in explaining the association with low birth weight. However, there were no differences in micronutrient intake when vitamin supplements were taken into account between the participant groups. In pregnant women who followed less strict forms of plant-based diets and consumed milk, eggs or fish, the researchers observed no negative effects at all.

Interestingly, the degree of effect on birth weight was comparable to that found among daily smokers compared to nonsmokers in this cohort. However, the findings are inconclusive given the small number of vegans in the study - just 18 out of 66,000 participants.

Despite the growing popularity of vegan diets in developed countries, especially among women, scientists call for caution when choosing a type of diet restricted in certain nutrients, and the need for more careful study of the impact of such diets on maternal and child health. It is important to take into account not only the fact of adherence to a vegan diet, but also the balance of nutrients necessary to ensure the full development of the child and maintain the health of the future mother, the researchers summarized.