Women who eat a better diet leading up to pregnancy are less likely to have babies with birth defects, including brain and spine problems as well as cleft lip and cleft palate, according to a US study.

Researchers found that fewer babies were born with defects such as neural tube defects when mothers-to-be more closely followed either a Mediterranean diet -- high in beans, fruits, fish and grains, and low in diary, meat and sweets -- or the US food guide pyramid guidelines for a healthy diet.

The findings were published in the Archives of Pediatrics and Adolescent Medicine.

"A lot of birth defects, including neural tube defects, occur very early in pregnancy, before women even know they're pregnant," said Suzan Carmichael from Stanford University, who worked on the study.

"These messages are important for women who are at any risk of becoming pregnant."

The bottom line for women who are pregnant, or may get pregnant, is eating a variety of foods, including a lot of fruit, vegetables and grain, and taking a vitamin supplement that contains folic acid, she added.

Low levels of folate during pregnancy were linked to brain and spinal birth defects in the late 1990s, and pregnant women are recommended to take a prenatal vitamin with folic acid and iron.

Carmichael and her colleagues wondered if eating a healthy, balanced diet could have the same protective effect as getting extra vitamins and minerals through supplements. They used data from the National Birth Defects Prevention Study to compare about 3,400 women who had a baby with a neural tube defect or a cleft lip or palate, and 6,100 women whose babies didn't have a birth defect.

Each of those women completed a phone interview in the two years after her baby was born.

Researchers asked the new mothers how frequently they had eaten a range of foods, from beans to candy, in the few months before they became pregnant. Then they calculated how closely women had followed the so-called "Mediterranean diet" ir the US Department of Agriculture's Food Guide Pyramid.

After taking into account how much the women weighed, whether they took vitamins and if they smoked and drank, Carmichael and her colleagues found that those who more closely followed either healthy diet were less likely to have babies with any of the birth defects they studied.

In particular, women with a diet closely matching the USDA Food Guide Pyramid were half as likely to have a baby missing part of its brain and skull -- a birth defect called anencephaly -- than women whose diet was farthest from those guidelines. They were also 34 percent less likely to have a baby with cleft lip and 26 percent less likely to have one with cleft palate.

Epidemiologist David Jacobs, from the University of Minnesota in Minneapolis, said the findings suggest that a healthy diet can lower the risk of birth defects in the same way that has happened through folic acid fortification.

"If you are a woman about to become pregnant or think you might become pregnant, it's all the more reason for you to take care of yourself and seek out better foods," Jacobs, who wrote a commentary accompanying the study, told Reuters Health.

Luz de Regil, from the World Health Organization's Department of Nutrition of Health and Development in Geneva, cautioned that with the current evidence about the benefits of prenatal supplements, a good diet isn't enough.

On a global scale, especially in places where diets aren't as good, folic acid is still a priority for preventing birth defects, she told Reuters Health.

"If a woman is trying to get pregnant, a good diet should be a complement to the use of folic acid supplementation, not a substitute," said de Regil, who wasn't involved in the study.

"Having a baby (and) a good pregnancy is a result of many things."