LONDON — A British study of how diet affects the health of new mothers and their babies produced the surprise finding that vegetarian women are more likely to have girls, one of the report's authors said Tuesday.
In what is thought to be the first study of its kind, researchers at Nottingham University in central England found significant differences in the sex of babies born to vegetarian and meat- and fish-eating women.
"We were very surprised. It was just a fluke, this was something we were never looking to find," Pauline Hudson, one of the report's authors, told Reuters.
"We were monitoring the health outcomes in vegetarian and non-vegetarian mothers, looking at things like hemoglobin levels, which shows how much iron the mother has in her blood, and birth weights."
Hudson, a midwife teacher, and co-author Rosemary Buckley monitored the 5,942 pregnant women seen at Nottingham's City Hospital during 1998, logging whether or not they were vegetarian — defined as avoiding meat and fish — when they were booked in.
Nearly 5 percent were vegetarian — more than 250 women.
"The birth ratio in Britain is that for every 106 boys born there are 100 girls, that's pretty constant," said Hudson. "In our sample group of vegetarians there were 81.5 boys born for every 100 girls."
To further test their surprise findings — and increase the sample number to what scientists call a "statistically significant" level — the pair extended their study for a further six months, looking just at the sex of babies.
The results, covering around 150 more vegetarian women, were "just about exactly the same."
The study also found that vegetarian mothers were less likely to smoke during pregnancy — 10 percent did so, compared with 20 percent of meat-eaters — and more likely to breast-feed — 80 percent against 60 percent.
These differences were attributed to the likelihood that a vegetarian and health-conscious lifestyle tend to go together, and that some vegan mothers choose to avoid bottled milk containing dairy products.
Previous studies have shown that diets high in potassium, calcium and magnesium will produce more male births, but there is no evidence that a vegetarian diet is low in these elements.
In an article outlining their findings in the British journal Practising Midwife, Hudson and Buckley suggest a further study could be carried out to investigate whether the diet of fathers affects the sex of their children.