Maternal Diet Study Sparks Controversy

A new study suggesting that maternal diet may influence the gender of offspring has experts concerned that women may starve themselves or overeat to conceive the baby of their preferred gender.

The study from Exeter University, UK, found a link between higher energy intake around the time of conception and the birth of sons. (Proc Biol Sci 2008 Apr 22; Epub ahead of print)

After viewing the research Dr. Tan Thiam Chye, obstetrician and gynecologist at KK Women's and Children's Hospital in Singapore and Dr. Kenneth Kwek, deputy chairman, division of obstetrics and gynecology and head, department of maternal fetal medicine, KK Women's and Children's Hospital raised doubts.

"We are concerned that some women may begin to starve or overeat during their peri-conception period for their desires on gender selection after reading this study without carefully analysis of the data," said Tan.

Fifty-six percent of women in the highest third of preconceptional energy intake bore boys as compared 45 percent in the lowest third.

Tan said although the nine percent difference is statistically significant "it may bear little clinical relevance," and as an observational trial it has "its biases and limitations." Tan did acknowledge that the "evolutionary hypothesis on the evidence of preconception diet of the mother on gender selection is interesting."

"We emphasize that a healthy diet before and during pregnancy is critical and should not be compromised in the false hope for a boy or girl, especially when such data is not conclusive and based on a few observational trials. We are not proponents of gender selection as having a healthy baby is far more important than the gender," concluded Kwek.

Dr. Fiona Mathews, lead author on the paper agreed with their concerns and emphasized all of the women in this study were eating diets within the normal range, and all were healthy.

"There were real differences in the chance of having a boy or a girl, depending on what the mother ate, but these differences were quite small.

"Until further trials are done, there is no evidence that the likelihood of having a boy could be increased beyond this by dietary means.

"There are many books and internet sites that claim it is possible to make much greater changes to the chance of having in infant of a particular sex by following extreme dietary regimes. These claim are not based on scientific evidence and would certainly not recommend that any woman embark on an unusual diet around the time of conception," she said.

Using data from 740 British women who were first-time mothers, unaware of their fetus's gender, the researches showed fetal sex is associated with maternal diet at conception.

Participants were asked to provide records of their eating habits before and during the early stages of pregnancy. They were then split into three groups according to the number of calories consumed per day around the time they conceived.

The study found that, as well as consuming more calories, women who had sons were more likely to have eaten a higher quantity and wider range of nutrients, including potassium, calcium and vitamins C, E and B12. There was also a strong correlation between women eating breakfast cereals and producing sons.

Intakes during pregnancy were not associated with sex, suggesting that the fetus does not manipulate maternal diet.

Mathews said the research may help to explain why in developed countries, where many young women choose to have low calorie diets, the proportion of boys born is falling.

"Our results support a hypothesis predicting investment in costly male offspring when resources are plentiful.

"Dietary changes may therefore explain the falling proportion of male births in industrialized countries," added Mathews.

Over the last 40 years there has been a small but consistent decline, of about one per 1,000 births annually, in the proportion of boys being born in industrialized countries, including the UK, the US and Canada.