A study of the impact of family planning on women's postpartum contraceptive use and birth spacing found that women who received free family planning services over 2 years increased contraceptive use by 5.9 percentage points.

They were also 43.5% less likely to have become pregnant again within 24 months as compared with the control group. The results suggest that family planning can improve women's long term reproductive health outcomes, including healthy spacing between pregnancies, according to the authors of the research.

Short pregnancy and birth intervals can adversely affect maternal and child health (MCH) and are associated with high levels of infant mortality and low birth weight, particularly in Sub-Saharan Africa. For these reasons, the World Health Organization (WHO) recommends that women wait at least 24 months after a live birth before attempting to become pregnant again.

However, family planning (FP) use in the postpartum period is low, and many women in low- and middle-income countries become pregnant within this 2-year window. Improving access to postpartum FP has the potential to reduce these high-risk short birth intervals, yet the unmet need for FP in the postpartum period and the risk of short birth intervals remain high, particularly in Sub-Saharan Africa.

Although there is a large empirical literature on FP, recent reviews of the impact of FP programs and interventions have found few high-quality studies that assessed intervention impact in the short term (within a year of intervention exposure) and even fewer studies that assessed outcomes beyond contraceptive use, such as pregnancy and births.

In Egypt, an intervention that provided women using lactation amenorrhea with emergency contraception in advance, as a backup contraceptive method, was found to reduce pregnancies after 6 months. In another study that was also conducted in Egypt, women who received an immediate postpartum insertion of an intrauterine device (IUD) were found to have lower pregnancy rates 1 year after insertion compared to women who received an insertion 6 weeks after delivery.

Other randomized controlled trials of FP services have found equally mixed results. Findings from the Navrongo community-level experiment in Ghana found program impacts on both contraceptive use and longer-term fertility; however, balance across treatment and control communities was not achieved, and recent studies have found that the effects of the intervention have attenuated over time.

Two program evaluations in Ethiopia and Kenya that assessed FP services that were integrated into microcredit and HIV programs, respectively, found no intervention effects.

Finally, studies of the well-known Matlab MCH-FP program in Bangladesh have shown significant and long-standing reductions in fertility and increased birth intervals among women in program areas. However, findings from the Matlab program have been extensively debated, with critics noting that the bundling of FP with other MCH services makes it difficult to disentangle the independent impacts of FP.

In addition, the potential nonrandom selection of intervention and comparison areas has sparked questions about the extent to which causal inferences can be made from the program. More recently, a cluster randomised controlled trial of a postpartum FP intervention in Burkina Faso found a significant effect on modern contraceptive use after 1 year of intervention exposure, but no effect after 2 years of exposure.

A randomised trial of a similar intervention in the Democratic Republic of Congo found no effect on overall contraceptive use, but there was an observed shift in the method mix toward contraceptive implants after a year of exposure to the intervention.

A cluster randomised controlled trial in Nepal, which improved women's access to FP counselling during pregnancy and provided women with the option to receive IUD insertions in the immediate postpartum period, found positive effects on modern contraceptive use 1 year after exposure to the intervention.

However, these findings were not sustained after 2 years of intervention exposure, with effects only being observed on the contraceptive method mix, mainly through an increase in IUDs and a reduction in other methods. Notably, these three randomized trials reported effects only on contraceptive use, but not on pregnancy or birth spacing.

A recent evaluation of an integrated postpartum FP intervention in Bangladesh, which had intervention and comparison areas, but was not randomised, did find a significantly lower risk of short birth intervals in the intervention areas over the first 36 months of exposure to the intervention.