Objectives: To determine, firstly, if there was any seasonal effect on nutrient intake during pregnancy and birth measures, secondly, if there was any relationship between maternal nutrient intake and infant birth measures according to season and thirdly, to consider the hypothesis that seasonal change in nutrient intake during pregnancy might affect health in later life of some women's offspring.
Design: Pilot study to determine number of days required to characterize group intake followed by a prospective cohort study.
Setting: Patients attending a city ante-natal clinic in the lower North Island, New Zealand.
Subjects: A total of 214 healthy mostly European pregnant women volunteers, entering the second trimester of pregnancy, of whom 10 miscarried and seven withdrew.
Methods: Subjects were visited in months 4 and 7 of pregnancy, and months 2, 6 and 12 after birth. Height, weight and skinfolds were measured and questionnaires to determine personal details administered at these times. Subjects recorded 8 days of weighed diets in both the fourth and seventh month. Health records were used to supply infant measures.
Results: Significant (P</=0.05) seasonal variations in fat, carbohydrate, vitamin C and D, B vitamins, beta-carotene, sodium, potassium, calcium, phosphorous, sulfur, sodium, chloride, zinc and selenium intakes were found. No significant 'main effect' difference in gestational age, infant birthweight, and head circumference was found with season. However, there were significant interactions (P</=0.05) for each birth season between birth measures and specific maternal nutrients at months 4 and 7 of pregnancy.
Conclusion: The significant seasonal variations in nutrient intake in pregnant women, and significant influence of nutrient intake on birth measures in different seasons, suggests seasonal nutrient variation may also affect fetal development at a cellular level. This supports our hypothesis that the development of conditions related to season of birth, including schizophrenia, multiple sclerosis, type I diabetes and longevity, may be influenced by seasonal variation in nutrient intake during pregnancy.