Diet in pregnancy and baby gender

Behind the Headlines

Tuesday March 9 2010

Can your diet during pregnancy affect your baby's gender?

“What women eat while they are in the early stages of pregnancy influences the sex and health of their unborn baby,” The Daily Telegraph reported. It said that eating breakfast and a high-fat diet around the time of conception made it more likely the offspring would be a boy.

The newspaper article is actually reporting two different studies. The findings about the effect of a high-fat diet and breakfast on a child’s gender are from a study in humans that the newspaper says was published two years ago.

The new study that has prompted this report was in mice, and it did not aim to look at whether a high fat diet during pregnancy affects the sex of offspring. The researchers’ main aim was actually to investigate whether the amount of fat in the diet of pregnant female mice affected gene activity in the placenta, and whether this varied depending on the gender of the foetus. Such research could potentially help to explain how maternal diet in pregnancy has an effect on offspring health.

There are many differences between mice and humans and these findings may not be representative of what happens in people. Further study in humans would be needed to establish if this were the case. Pregnant women should aim to have a healthy balanced diet to maintain good health in themselves and their offspring.


Where did the story come from?

Dr Jiude Mao and colleagues from the University of Missouri and GenUs BioSystems, Inc carried out this research. The study was funded by the National Institutes of Health. The study was published in the peer-reviewed medical journal Proceedings of the National Academy of Sciences of the USA.

The Daily Telegraph reported this study. The article presents the study’s findings and does say that the current research is in mice. It also refers to a previous study looking at the effect of diet on baby gender in humans, but this study is not assessed here. The reporting of the findings of this previous study, which had different aims to the current research, could lead to confusion about what the new research has found.


What kind of research was this?

This research in pregnant female mice examined how maternal diet affected the activity of genes in the cells of the placenta that was supporting each male or female foetus. The researchers say that diet during pregnancy affects the future health of offspring, and that the effects differ for foetuses of different genders. Therefore, they wanted to look at whether they could find differences in gene expression in the placenta that could potentially account for these effects.

Studies such as this are useful in that they help scientists to understand how certain environmental conditions might affect health. However, differences between the species may mean that results obtained in mice may not be representative of what happens in humans.


What did the research involve?

The researchers fed female mice one of three diets from the age of five weeks: a very high-fat diet, a low-fat high in carbohydrate diet, or a chow diet with a level of fat between these two extremes. These mice were mated at 35 to 40 weeks of age and the pregnant mice studied further. The researchers then looked at the activity of a large panel of genes in the placentas of the mice at 12.5 days of pregnancy. They looked at whether the pattern of activity was affected by diet and by the gender of the foetus.


What were the basic results?

The three maternal diets affected the activity of 1,972 genes in the placentas, with the differences in activity at least double between at least one pair of diets. The differences were more pronounced in female foetuses than in males. Each diet showed a distinct pattern of gene activity depending on the gender of the foetus.

The genes that were affected by diet are usually involved in kidney function and in sensing odours.

The researchers report that there was a tendency for more female offspring in the low-fat, high-carbohydrate diet group, but that there were too few offspring in the very high-fat diet group to determine the statistical significance of this.


How did the researchers interpret the results?

The researchers conclude that gene activity in the placenta of mice is affected by maternal diet and foetal gender. The placentas of female foetuses are more sensitive to maternal diet than the placentas of male foetuses.



This study investigated how the mother’s diet in pregnancy might have an effect on the developing foetus. The researchers aimed to identify alterations in the activity of genes in the placenta that could potentially contribute to this effect. They found a number of changes in gene activity as a result of different maternal diets in mice, and that these changes were also affected by the gender of the foetus. However, differences between the species may mean that results obtained in mice may not be representative of what happens in humans.

This study did not aim to investigate whether maternal diet in pregnant mice affects the gender of their offspring.

The developing foetus obtains nutrition and oxygen, and also eliminates waste, via the placenta. Therefore changes in the placenta, such as changes in placental gene activity due to diet and foetus gender, could potentially influence foetus health and possibly survival. However, as the authors themselves acknowledge: “The reason why a maternal high-fat (low-carbohydrate) diet favours survival of sons while a maternal low-fat (high-carbohydrate) diet results in more daughters continues to elude us.”

Analysis by Bazian

Edited by NHS Choices

Links to the headlines

Eating breakfast and fatty diet during early pregnancy increases chances of having a boyThe Daily Telegraph, March 9 2010

Links to the science

Mao J, Zhang X, Sieli PT, et al. Contrasting effects of different maternal diets on sexually dimorphic gene expression in the murine placentaPNAS 2010; Published online before print


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