TUESDAY, Aug. 25, 2015 (HealthDay News) -- Women who eat healthy diets prior to pregnancy are less likely to have a baby born with a heart defect, researchers report.
Women who followed a very healthy diet were 37 percent less likely than those who ate poorly to have a baby with tetralogy of Fallot, a complex heart defect that causes babies to turn blue because their blood can't carry enough oxygen. The women also were 23 percent less likely to have a baby born with an atrial septal defect, or a hole in the wall that separates the top two chambers of the heart, the study found.
Women and their babies benefited most from a diet rich in vegetables, fruits, nuts, legumes, whole grains and fish, with limited intake of dairy, meat and sweets, the researchers found. Foods rich in nutrients like folic acid, iron and calcium were also considered healthy, the study authors said.
"The more you went up in diet quality, the less the risk for severe congenital heart anomalies," said lead author Dr. Lorenzo Botto, a professor of pediatrics and a medical geneticist at the University of Utah School of Medicine.
However, this study didn't prove a cause-and-effect relationship between a healthy diet and a lower risk of heart birth defects. The research only showed an association between the two.
The study appears in the journal Archives of Disease in Childhood (Fetal & Neonatal Edition).
Congenital heart defects affect one of every 100 newborns in the United States, and cause nearly one out of every four infant deaths related to birth defects, according to background information in the study.
"They are common, they are critical and we really don't know how to prevent them," Botto said.
The new study was inspired by earlier findings that a high-quality diet could reduce the risk of birth defects such as cleft palate or spina bifida, Botto said.
The research team evaluated data from almost 10,000 mothers of babies born with heart defects, and about 9,500 mothers of healthy babies. The babies were born between October 1997 and December 2009, and are part of the larger, federally funded National Birth Defects Prevention Study, Botto said.
Mothers were asked about what they ate in the year prior to their pregnancy. Researchers graded their diet based on how closely it followed the Mediterranean Diet and the Diet Quality Index for Pregnancy, a common diet plan recommended to expecting mothers.
The Diet Quality Index provides positive scores for grains, vegetables, fruits, folate, iron and calcium, and negative scores for calories from fats or sweets. The Mediterranean Diet emphasizes legumes, grains, fruits, nuts, vegetables and fish, and discourages dairy, meat and sweets.
Mothers who scored in the top 25 percent of dietary quality had a significantly lower risk of having a baby born with a heart defect, compared with those who scored in the bottom 25 percent, the study found.
Eating right appears to boost the mother's health, which in turn boosts the likelihood that the developing fetus will be able to withstand genetic or environmental factors that might cause a heart defect, Botto said.
"We know that having a healthy woman tends to lead to a healthy baby," he said.
The findings support the need for women to eat a healthful diet even before they have conceived, since birth defects can occur very early in pregnancy. If a woman waits to eat right after she's pregnant, it could be too late, the researchers said.
"We know that birth defects happen in the very first weeks after conception. For heart anomalies, the first four to seven weeks," Botto noted.
Dr. Edward McCabe, senior vice president and medical director of the March of Dimes, agreed.
"It would be great if all women of childbearing age, for their own benefit and their future child's benefit, could be on an optimal diet," McCabe said. "If not, then plan and get on a diet for a year before you conceive."
By extension, this strategy also calls for strong family planning, so a woman can take the time to establish a solid dietary foundation for her pregnancy if she isn't already eating healthy, he added.
"One of the key messages to me is the importance of planning to have a baby," McCabe said. "Fifty percent of the babies in the U.S. are not planned. We really feel it's important for women to plan their pregnancy, and we know it's important for them to be on an optimal diet before they become pregnant."
Despite the study results, both Botto and McCabe noted that at this time researchers still don't know exactly why a healthy diet appears to provide such strong protection against birth defects.
"We don't know why it works, but we know it works," McCabe said. 'People can go on researching the cause for decades, but even if we don't know the cause, we know the cure."
For more information on pregnancy and nutrition, visit the U.S. National Institutes of Health.