Object. The study aimed to compare the pregnancy outcome among multivitamin users and non-users during pregnancy. Methods. The prospective HAPPY PREGNANCY cohort study (Development of novel non-invasive biomarkers for fertility and healthy pregnancy, 2013–2015) recruited 2334 unselected pregnant women at the Women’s Clinic, Tartu University Hospital, Estonia. Use of multivitamins and food supplements was assessed by using questionnaires during each trimester (response rate 94–98%), information about the pregnancy course and outcome was obtained from medical records.
Results. 56%, 66.9% and 65.4% of the pregnant women used multivitamins during the first, second and third trimesters, respectively. The prevalence of gestational hypertension (overall prevalence in the whole cohort 3%), preeclampsia (2.7%), gestational diabetes (5.7%), birth of smallfor-gestational-age baby (8.4%), caesarean section rate (17.1%) did not differ among the multivitamin users and non-users. Among the multivitamin users during the first and second trimesters, only 4.6% and 3,8% of the cases resulted in preterm birth (PTB, < 37. gestational weeks) versus 6.8% and 7.1% among the multivitamin non-users (p = 0.036 and 0.002, respectively). Vitamin C users during the first trimester of pregnancy had less PTB (4,3%) compared to the vitamin C non-users (7%; p = 0.014). In women with known risk factors (previous PTB, twins, smoking, IVF pregnancy, low body-mass index; n = 418) multivitamin supplementation did not reduce the risk for PTB (OR 0.63 [95% CI 0.34-1.3], p = 0.23), whereas in those without risk factors (n = 1865), multivitamin use during the second trimester reduced the risk two times (OR 0.51 [95% CI 0.310.85], p = 0.01). Overall, multivitamin use during the second trimester reduced the risk for PTB.
Conclusions. Use of multivitamins during the second trimester of pregnancy may reduce the risk for PTB among low-risk women. In the presence of the risk factors for PTB, the effect of multivitamin supplementation remains limited.