The relationship between dietary supplement use in late pregnancy and birth outcomes: a cohort study in British women

Na Alwan,Dc Greenwood,Je Cade,Nab Simpson,Hj Mcardle

doi:10.1111/j.1471-0528.2010.02549.x

Abstract

ObjectiveTo examine the relationship between dietary supplement use during pregnancy and birth outcomes.DesignA prospective birth cohort.SettingLeeds, UK.SampleOne thousand two hundred and seventy-four pregnant women aged 18–45 years.MethodsDietary supplement intake was ascertained using three questionnaires for the first, second and third trimesters. Dietary intake was reported in a 24-hour dietary recall administered by a research midwife at 8–12 weeks of gestation. Information on delivery details and antenatal pregnancy complications was obtained from the hospital maternity records.Main outcome measuresBirthweight, birth centile and preterm birth.ResultsReported dietary supplement use declined from 82% of women in the first trimester of pregnancy to 22% in the second trimester and 33% in the third trimester. Folic acid was the most commonly reported supplement taken. Taking any type of daily supplement during any trimester was not significantly associated with size at birth taking into account known relevant confounders. Women taking multivitamin-mineral supplements in the third trimester were more likely to experience preterm birth (adjusted OR = 3.4, 95% CI 1.2, 9.6, P= 0.02).ConclusionsRegular multivitamin–mineral supplement use during pregnancy, in a developed country setting, is not associated with size at birth. However, it appears to be associated with preterm birth if taken daily in the third trimester. The mechanism for this is unclear and our study’s findings need confirming by other cohorts and/or trials in developed countries.

Highlights

Multivitamin–mineral supplements during pregnancy are becoming an attractive option considered by international agencies to improve the nutritional status of pregnant women in developing countries
When we looked at taking particular types of supplements, taking a daily multivitamin–mineral preparation at any stage in pregnancy was not associated with size at birth using the continuous outcomes of birthweight in grams and customised birth centile, as well as the binary outcome of small-for-gestational-age (Table 4)
Taking multivitamin–mineral supplement preparations during the third trimester was associated with an increased risk of preterm birth

Summary

Introduction

Multivitamin–mineral supplements during pregnancy are becoming an attractive option considered by international agencies to improve the nutritional status of pregnant women in developing countries. They are considered relatively cheap, feasible and have the potential to improve maternal nutrition when administered through national. Dietary supplements are not subject to the same rigorous safety and efficacy standards as prescription medications.[1] Their proposed use during pregnancy is supported by findings from several randomised controlled trials in developing country settings, where deficiency in micronutrients is more prevalent. Studies in Nepal, India, Indonesia, Guinea-Bissau and Tanzania have shown positive effects on adverse birth outcomes such as infant mortality and low birthweight.[2,3,4,5,6] other trials in Nepal, Mexico and Zimbabwe have failed to demonstrate a significant effect on the incidence of low birthweight,[7,8,9,10] and some have even demonstrated an increased a 2010 The Authors Journal compilation a RCOG 2010 BJOG An International Journal of Obstetrics and Gynaecology risk of adverse outcomes.[10,11] According to a Cochrane systematic review, there is currently insufficient evidence to suggest replacement of iron and folate supplementation with multiple micronutrient supplements and further research is needed to quantify the degree of maternal or fetal benefit and to assess the risk of excess supplementation and the potential for adverse interactions between the micronutrients.[12]

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Discussion

Conclusion