Hormonal contraception and hemoglobin levels in urban Malawi: a longitudinal analysis

Studies have highlighted potential non-contraceptive benefits from women’s use of hormonal, reversible contraceptive methods. Given the physiological pathways through which hormonal contraception may interact with menstruation, a growing body of work has documented the extent to which hormonal method use might be associated with increased hemoglobin levels and reductions in the risk of anemia in women. While these findings are promising, the scope for causal inference from these studies is restricted by their cross-sectional design, which limits the extent to which bias from individual-level confounding can be mitigated. We leverage three years of annual, woman-level panel data from a randomized controlled trial for 2143 women from urban Malawi to assess the relationship between women’s use of hormonal contraception and their risk of anemia, controlling for individual woman fixed effects. We compare our panel results with standard cross-sectional estimates from the same sample. We find that hormonal method use is associated with increased levels of hemoglobin in women, though the effects are different for different hormonal methods. Adoption of an injectable is associated with a 3.7 g/cL increase, and adoption of an implant a 5.7 g/cL increase, in hemoglobin levels. Our estimates are consistent across cross-sectional and panel model specifications, suggesting that existing cross-sectional estimates may be reliable. Our findings highlight potential health benefits from hormonal contraceptive use that extend beyond pregnancy prevention. These benefits, in turn, have significant implications as to how women are counseled on contraception both within family planning and nutrition programs. This trial was registered at the American Economics Association Registry for randomized controlled trials on May 7, 2015 (AEARCTR-0000697) and at the Registry for International Development Impact Evaluations (RIDIE) on May 28, 2015 (RIDIE-STUDY-ID-556784ed86956). The use of hormonal, reversible contraception might have potential non-contraceptive benefits in addition to reducing the risk of pregnancy. There is cross-sectional evidence that women using hormonal methods have higher hemoglobin levels, and lower likelihood of anemia, than non-hormonal method users; however, this cross-sectional association may be due to differences between the types of women who use different contraceptive methods. To control for this individual (woman-level) heterogeneity, we use three waves of annual panel data from urban Malawi to study the relationship between changes in hormonal contraceptive use and changes in hemoglobin levels. We find that adopting a hormonal method is associated with an increased level of hemoglobin, though different hormonal methods appear to have different effect sizes. Our findings suggest that hormonal contraception may confer additional health benefits beyond their primary function to prevent pregnancy. We highlight the importance for women to be counseled on these benefits so that they are able to make more informed decisions over their contraceptive use and choice of method.