NEW YORK (Reuters Health) - Norwegian mothers-to-be who maintained "prudent" eating patterns during pregnancy were less likely to have preterm births compared to women who ate a more typically "Western" diet, according to a new study.
Both prudent and traditional Scandinavian eating patterns were linked to a lower likelihood of early delivery, according to the results published in the British Medical Journal.
While the observations don't prove cause and effect, the authors say, the findings support the idea that dietary advice should be given to pregnant women.
"Diet really matters when it comes to preterm delivery and it is very important for pregnant women to choose or to increase the intake of an overall healthy diet consisting of fresh and raw vegetables, fruit, whole-grain products, certain fish and to drink water," Dr. Linda Englund-Ögge told Reuters Health in an email.
Englund-Ögge, who led the new study, is with the Department of Obstetrics and Gynecology at the Institute of Clinical Sciences in the Sahlgrenska Academy at the Sahlgrenska Hospital in Gottenburg, Sweden.
"Preterm delivery is a major clinical problem - children born preterm are at severe risks of short and long term neonatal morbidity and almost 75 percent of all neonatal deaths, are found in this group," Englund-Ögge said. "In the U.S. more than one in ten deliveries are considered preterm."
Englund-Ögge added that in recent years there has been an increased awareness of whether maternal diet can affect the risk of preterm delivery so her study team wanted to know if the condition could be prevented by choosing or avoiding certain foods.
They identified 66,000 women who participated in the Norwegian Mother and Child Cohort Study and were pregnant between 2002 and 2008.
The women answered health questionnaires when they were 15 weeks pregnant and again two to seven weeks later. The first questionnaires were about their lifestyle, background, illness and related health factors. The second questionnaire assessed the women's eating habits from the time their pregnancies started.
The researchers used the questionnaire information to place the women into one of three groups of eating patterns, prudent, traditional or Western.
The prudent dietary pattern included raw and cooked vegetables, salad, onion/leek/garlic, fruit and berries, nuts, vegetables oils, water as a beverage, whole grain cereals, poultry and fiber-rich bread.
The traditional diet included foods like boiled potatoes, fish products, gravy, lean fish, margarine, rice pudding, low-fat milk and cooked vegetables.
The Western diet included more salty snacks, chocolate and sweets, cakes, French fries, white bread, ketchup, sugar-sweetened drinks, processed meat products and pasta.
The researchers also wanted to assess how well the women adhered to their diets.
"It is very rare that someone does not choose any considered unhealthy food at all during pregnancy, even those women with the healthiest lifestyles," Englund-Ögge said. "Therefore, all women were given pattern scores for the dietary patterns."
Englund-Ögge added that women with overall healthy diets who sometimes chose unhealthy food during pregnancy scored higher on the healthy dietary patterns than women who usually chose unhealthy foods.
"In this way, there is a gradient created in pattern scores that was investigated," she said. "It is also important to keep in mind that a low score of the healthy dietary pattern could be interpreted as an unwholesome diet."
There were a total of 3,505 preterm deliveries. The researchers found that women who adhered most closely to the prudent diet were 11 percent less likely to have preterm deliveries compared to women who didn't follow the diet as closely.
The women who adhered to the traditional diet most faithfully were 10 percent less likely to have preterm deliveries compared to women who had the lowest adherence scores in that group.
"We would like for doctors, midwives and all others who work with pregnant women to reinforce the important message that pregnant women should be encouraged to eat a balanced and healthy diet," she said.
"There are modifiable risk factors that people can address to enhance their pregnancy outcomes," Dr. Louis Muglia told Reuters Health.
Muglia is co-director of the Perinatal Institute and director of the Center for Prevention of Preterm Birth at the Cincinnati Children's Hospital in Cincinnati. He was not involved in the study.
"I actually thought it was quite a nicely done study and in many respects confirms what we know - that leading a healthier lifestyle contributes to better pregnancy outcomes - and one substantial component of that is your overall nutritional intake pattern," he said.
Based on this study, he said, a balanced diet with more foods rich in vitamins and other micronutrients probably facilitates a full-term pregnancy.
The study authors were cautious about saying the women's diets were the reason for their outcomes, Muglia noted, "because the individuals who had the prudent dietary intake patterns also had many other beneficial lifestyle habits that you might think would also improve the likelihood of good pregnancy outcomes."
He explained that the women in the study who followed the prudent diet generally had healthier weights, they probably smoked less and they were more educated.
"So I think there are a lot of things that go along with that prudent lifestyle that increases the likelihood of having a healthy pregnancy and reduces the likelihood of a preterm birth as well," Muglia said.
In an editorial that accompanied the paper, Lucilla Poston wrote, "The authors build on several studies that have proposed the benefit of a diet rich in fruit and/or vegetables in prevention of premature birth, including a recent report in this journal showing that fruit intake before pregnancy is a factor that relates to healthy outcome in (first-time mothers)."
Poston is a researcher and head of the Division of Women's Health at St. Thomas Hospital at King's College in London. She was not involved in the study.
"Health professionals would therefore be well advised to reinforce the message that pregnant women eat a healthy diet," she wrote.