Abstract
INTRODUCTION: Contraceptive use may affect women's nutritional status through birth spacing, parity, age at first birth, menstruation changes, and increased income. To inform the integration of family planning with nutrition interventions, we synthesised evidence linking the use of family planning to nutritional outcomes in women of reproductive age (15-49 years) and adolescents (10-19 years) in low- and middle-income countries (LMICs). METHODS: We searched PubMed, Embase, Web of Science and Cochrane Library for randomised controlled trials (RCTs), cluster RCTs, non-randomised trials and cohort studies published from 2000 onwards. Family planning exposure included any contraception type with no restrictions by comparison arms. Outcomes were maternal anthropometry and iron-status indicators. Random effects meta-analyses were done for comparisons with a minimum of three studies sharing intervention arms, outcomes and study design. Risk of bias and certainty of evidence were assessed. RESULTS: Of 20 097 publications, 99 were eligible for inclusion, covering 29 outcomes and 23 interventions (eg, oral contraception, intrauterine devices (IUD)). In 28 instances, at least three studies matched on intervention arms, outcomes and study design. Meta-analysis of RCTs showed that users of hormonal IUDs had significantly higher haemoglobin than oral contraceptive users (four studies; mean difference=1.25 g/dL; 95% CI: 0.38, 2.12; certainty=very low). Users of any hormonal contraceptive had a small reduction in body mass index (BMI) compared with non-contraceptive controls (seven studies; mean difference=-0.28 kg/m2; 95% CI: -0.52 to -0.04; certainty=low); however, most samples were women with polycystic ovarian syndrome. Other relationships were very uncertain and not statistically significant. CONCLUSION: Evidence is weak suggesting that hormonal IUDs increase haemoglobin compared with oral contraceptives and that any hormonal contraceptive use reduces BMI. Hormonal IUDs likely limit blood loss from menstruation, allowing for higher haemoglobin than oral contraceptives. Mechanisms for lower BMI after hormonal contraceptive use remain unclear. More robust evidence is necessary to guide policy. PROSPERO REGISTRATION NUMBER: This review was registered prospectively with the International Prospective Register of Systematic Review (PROSPERO ID: CD42023400069).