A pre-pregnancy diet rich in green leafy vegetables and fresh fruit could reduce by up to 50 per cent the risk of a baby being born underweight and undernourished, a study shows.
The Screening for Pregnancy Endpoints (Scope) study of pregnant women from New Zealand, Australia, Ireland and Britain found a healthy diet before conception reduced the risk of under-sized babies in women with normal blood pressure.
Women who ate three or more portions of vegetables a day were found to be 50 per cent less likely to have an under-sized baby, and women who had less than one portion of fruit a week were 50 per cent more likely to have a small baby.
Those with a high intake of oily fish - three or more servings a week - showed a 60 per cent reduction in under-sized infants.
Auckland University department of obstetrics and gynaecology Professor Lesley McCowan said the study of more than 3500 pregnant women reinforced the importance of eating a balanced diet before and during pregnancy.
"Pregnancy, and where possible prior to the pregnancy, may well be the ideal times to encourage women to adopt a healthy diet, improve their intake of important nutrients, and make lifestyle changes to reduce their risk of obesity," she said.
But while nutrients found in fruit and vegetables could protect both mother and fetus, woman who ate such foods were also likely to lead healthier lifestyles, shesaid.
The study, published in BJOG: An International Journal of Obstetrics and Gynaecology, aimed to develop screening tests for undersize babies, pre-eclampsia and spontaneous preterm births.
Dr McCowan said too-small infants were more likely to be stillborn or have complications.
"Less than one-third of these at-risk babies are identified before birth in current antenatal practice," she said.
"Improved identification of these vulnerable infants, by screening early in pregnancy, therefore has the potential to reduce stillbirths and complications in the newborn period.
"In the Scope study, our findings show that the risk factors for the majority group of [too-small] infants with mothers with normal blood pressure included low fruit intake in the three months before pregnancy, cigarette smoking, increasing maternal age, daily vigorous exercise, being a tertiary student, and the pregnant woman being born with a low birth weight herself."
At 15 weeks gestation, smoking was found to increase the risk of having an undersized baby by 30 to 60 per cent for every five cigarettes smoked a day.
Dr McCowan said risk factors for undersized infants in mothers with high blood pressure included conception by in vitro fertilisation and previous early pregnancy loss.
BJOG editor Philip Steer said pregnant woman needed to eat fewer takeaways and more fresh fruit and vegetables.
"This study emphasises the importance of good diet and nutrition. Unfortunately, many people find it difficult to resist the temptations of 'junk' food."