The results were published in the prestigious British Medical Journal in 2014.
The researchers used data from 66,000 pregnant women participating in the Norwegian Mother and Child Cohort Study. In mid pregnancy, the women answered a general questionnaire on lifestyle, disease and health in early pregnancy and a dietary questionnaire that captured food habits during the first part of the pregnancy.
Three main dietary patterns
Using an analysis that takes into account the combination of all foods and the correlation between food items, the researchers were able to identify three overall dietary patterns; a prudent pattern, a Western pattern and a traditional Norwegian pattern.
The prudent pattern was characterised by a high intake of vegetables, fruits, berries, nuts, vegetable oils, water as beverage, whole grain cereals, poultry, and fibre rich bread.
The Western pattern was characterised by a high intake of salty and sweet snacks, white bread, cakes, desserts, processed meat products and sugary carbonated drinks.
The traditional Norwegian dietary pattern was characterised by a high intake of boiled potatoes, fish products, lean fish, gravy, margarine, rice porridge, low fat milk and cooked vegetables.
All the women were assigned scores for each of the patterns. Dietary pattern analysis captures a broader picture of dietary quality than studying individual foods or nutrients.
The researchers found that women with high scores for the prudent and traditional patterns had a lower risk of giving birth prematurely, i.e. delivery before 37 weeks of gestation, than women with low scores on these dietary patterns.
“Our results suggest that it is more important for pregnant women to increase their intake of vegetables, fruit, whole grains and fish than to totally avoid eating processed food, pizza and chips,” says Brantsæter.
Brantsæter emphasises the need to examine all possibilities to prevent preterm delivery because it can lead to an increased disease risk in the child at birth and in the longer term. 75 percent of all deaths associated with childbirth happen among preterm infants.
“There are many risk factors that can lead to preterm delivery birth, such as smoking and obesity but until now there has been little research on the relationship between dietary patterns and birth outcome”, says Brantsæter.
This study is the first to have analysed dietary patterns (principal component analysis) to look at the relationship between food intake and premature birth.
This study supports previous research showing that foods that are associated with reduced risk of spontaneous preterm birth are part of the prudent dietary pattern. The foods included in both this pattern and the traditional dietary pattern largely support the Norwegian Directorate of Health’s recommendations for a healthy diet.
Previous studies in the Norwegian Mother and Child Cohort Study have also shown that a similar dietary pattern characterized by e.g. vegetables, fruits, vegetable oils and poultry was associated with reduced risk of pre-eclampsia, and that mothers who follow the dietary recommendations are more likely to avoid excessive weight gain in the months after birth.
Large variations in diet
Adherence to the dietary patterns differed with age, educational attainment, and number of previous births. Older mothers, first-time mothers, non- smokers and mothers with higher educational attainment had higher scores on the prudent dietary pattern.
“First time mothers had a significantly higher score for a wholegrain and greens diet. This may mean that they are more concerned with their diet during pregnancy than women who have given birth to more children, or it could mean that women who have given birth to more children know that the risk of giving birth prematurely is lower in subsequent pregnancies”, says Brantsæter.
“It is a great strength that the Norwegian Mother and Child Cohort Study includes so many pregnant women from all over Norway and that we have information about a variety of background factors that are important to take into account when studying the relationships between diet and birth outcomes”, says Brantsæter.
Important nutritional guidance
“Although these findings cannot establish causality, our research shows that the current dietary advice is sound. We would like to inspire doctors, midwives and others who advise pregnant women to pay more attention to dietary counselling and discuss the importance of diet in pregnancy. We want more emphasize on the finding that regular consumption of healthy food is more important than focusing on reducing consumption of unhealthy food”, concludes Brantsæter.
Englund - Ögge L, Brantsæter AL, Sengpiel V, Haugen M, Birgisdottir BE, Myhre R, Meltzer HM, Jacobsson B. Maternal dietary patterns and preterm delivery - results from large prospective cohort study. BMJ (2014)