Iron supplementation in pregnancy--does the preparation matter?

OBJECTIVE: To assess the use, side effects and discontinuation rates of iron preparations during pregnancy.
DESIGN: Six hundred and twelve randomly selected postpartum women completed a questionnaire on iron supplement use in the second and third trimesters.
RESULTS: Of the 517 women (84.5%) reported using iron supplements, 453 were eligible for the study. The most common preparation was ferrous fumarate (46.8%, P < 0.01), followed by ferrous sulfate (31.8%), ferric polymaltose (12.4%), and ferric bisglycinate (7.3%). Almost half the participants (45%) reported at least one adverse effect, especially constipation (27.4%, P < 0.01), nausea (10.8%). Multivitamin preparations and ferric bisglycinate were associated with the fewest side effects (23.7, 21.2% respectively, P < 0.01), and ferrous fumarate and immediate-release ferrous sulfate with the most (56.3, 53.7% respectively). Eighty-three women discontinued their originally prescribed iron preparation, mainly (89%) due to side effects. Discontinuation rates were lowest for the multivitamin and ferric bisglycinate (10.5, 9.1%, respectively). In most cases, the specific preparation was recommended by the women's physician (76%).
CONCLUSION: Ferrous fumarate-containing multivitamin preparations and ferric bisglycinate, although infrequently recommended as the first-line of iron supplementation, may be associated with less side effects and better compliance.