Maternal dietary intake of riboflavin and vitamin C in early second trimester, foetal growth and birth outcome - a cohort study
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Background: The focus on riboflavin and vitamin C inthis study emanated from their important physiological functions. Reported studies of the association between maternal dietary intake of riboflavin and vitamin C, and birth anthropometry show conflicting results and it is not known whether their intakes influence intrauterine growth. Gender-specific differences in foetal response to nutritional and environmental factors during pregnancy have been suggested. Objectives:To examine whether maternal dietary intake of riboflavin and vitamin C around 17-20 weeks of gestation is associated with foetal growth and birth weight, and if the association is gender specific. Design:Prospective cohort study conducted 1986-1988 and designed to examine factors related to intrauterine growth. Setting:Routine pregnancy care, special study visits, and University hospital in Bergen and Trondheim with surroundings. Participants: 872 women of Caucasian origin and their second or third singleton offspring. Main outcome measures:Weight deviation (in per cent) from normal weight for the estimated gestational age based on ultrasound measures around 25, 33 and 37 weeks of gestation, and birth weight. Methods: Information on maternal riboflavin and vitamin C intake was obtained from 3-d dietary records. Before statistical analysisthe intakes were categorized by dividing the frequency distribution into tertiles. Cross-sectional, covariate adjusted multiple linear regression analyses were performed by vitamin and foetal gender. The following covariates were considered: total energy intake, maternalage at study entry, pre-pregnancy body mass index, maternal smoking during pregnancy, highest completed education, previous number of births, and serum ferritin. In addition, for female offspring the analysis regarding maternal riboflavin intake and birth weight was also adjusted for gestational age at delivery. Results: We observed no association between maternalriboflavin intake and estimated foetal weight deviation during the second or third trimester. Unlike univariate analysis, multivariate analysis showed a borderline significant inverse association between maternal riboflavin intake and birth weight, - 56 g (95% confidence interval -77 to 4) for female infants. There was no such association for males. Maternal vitamin C intake was unrelated to estimated weight deviation at 25 and 33 weeks of gestation in both genders. At 37 weeks of gestation the association was borderline significant for male fetuses only, 1.1% (95% confidence interval -0.1 to 2.3). One unit (tertile) change in vitamin C intake was associated with a 71 g (95% confidence interval 9 to 132) increase inbirth weight in female infants. Again, no association was observed among males. Conclusions We found a borderline significant inverse association between maternal riboflavin intake and birth weight for female, but not for male infants. For both genders there was no association with the estimated foetal weight deviation. There was also a significant positive association between maternal intake of vitamin C and birth weight for female infants and a borderline significant positive association with estimated foetalweight deviation for male foetuses in late third trimester (gestational week 37). Our findings should be interpreted cautiously. Besides some concern about the validity ofdietary intake data, the choice of statistical methods could be questioned. Further, the borderline significant and significant findings may be biased by uncontrolled confounding, or be related to other factors than maternal riboflavin or vitamin C intake per se. Therefore, further studies are needed to elucidate the potential role of riboflavin and vitamin C in foetal growth. Studies should focus on intrauterine growth as a longitudinal process in addition to a continued focus on possible gender-specific differences, and preferably by adding biomarkersof different nutrients. Also, warranted are studies of overall dietary patterns or diet quality, for instance in combination with important environmental exposures and lifestyle factors,and their association with the outcomes under study. To our knowledge, this is the first study that has combined data on maternal vitamin intake, foetal growth and birth weight. Hence, it is also the first study to indicate a possible gender specific influence of riboflavin and vitamin C intake on estimated foetal weight deviation/birth weight.