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Randomized Controlled Trial
. 2008 May 15:8:17.
doi: 10.1186/1471-2393-8-17.

Effect of iron content on the tolerability of prenatal multivitamins in pregnancy

Patricia Nguyen  1 , Alejandro Nava-Ocampo, Amalia Levy, Deborah L O'Connor, Tom R Einarson, Anna Taddio, Gideon Koren
Affiliations
Randomized Controlled Trial

Effect of iron content on the tolerability of prenatal multivitamins in pregnancy

Patricia Nguyen et al. BMC Pregnancy Childbirth. .

Abstract

Background: Gastrointestinal irritability can deter pregnant women from starting or continuing prenatal multivitamin supplementation. In a previous study, suboptimal tolerability was observed among pregnant women taking a large tablet (18 mm x 8 mm x 8 mm) multivitamin with high elemental iron content (60 mg as ferrous fumarate). The objective of the present study was to compare rates of adherence and reported adverse events among pregnant women who were randomized to commence supplementation with a small-tablet prenatal multivitamin, containing either low or high iron content.

Methods: Pregnant women who called the Motherisk Program (Hospital for Sick Children, Toronto) and had not started taking or had discontinued any multivitamin due to adverse events were included in this prospective, randomized, open-label, 2-arm study. Women were randomized to take a small-size (16 mm x 9 mm x 4 mm), low elemental iron content (35 mg as ferrous fumarate) multivitamin ('35 mg' group); or a small-size (5 mm radius, 5 mm thickness), high elemental iron content (60 mg as ferrous sulphate) multivitamin ('60 mg' group). Follow-up interviews documented pill intake and adverse events. Rates of adherence and adverse events were compared between groups using chi-squared tests and Kaplan-Meier survival curves.

Results: Of 167 randomized women, 92 in the '35 mg' group and 75 in the '60 mg' group were included in the analysis. Despite ideal conditions and regular follow-ups, mean adherence based on pill intake recall, in both groups was approximately 50%. No statistically significant difference was detected in proportions of women who actually started taking either multivitamin. Among those who started, no difference was detected in rates of adherence or reported adverse events.

Conclusion: The present results suggest that iron content is not a major determinant of adherence to prenatal multivitamins. Combined with our previous study, tablet size may be the more definitive factor affecting adherence.

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Figures

Figure 1
Figure 1
Enrolled subjects and data collected. Total no. of subjects who completed the study, n = 140. Total no. of subjects with (complete or partial) data collected for study, n = 158.
Figure 2
Figure 2
Rates of adherence between 2 prenatal multivitamin groups, represented as Kaplan-Meier survival curves and based on the proportion of subjects with standard adherence (80% or greater pill intake), once supplementation commenced. (Black solid line) 35 mg iron group, n = 57. (Black broken line) 60 mg iron group, n = 47.
Figure 3
Figure 3
Rates of adherence between 2 prenatal multivitamin groups, represented as Kaplan-Meier survival curves and based on the proportion of subjects who commenced and continued supplementation with assigned multivitamin (at any percentage of pill intake). (Black solid line) 35 mg iron group, n = 57. (Black broken line) 60 mg iron group, n = 47.
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References

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