Objective To measure whether there was an association between the introduction of an output-based voucher programme and the odds of a facility-based delivery in two Nairobi informal settlements.

Data sources Nairobi Urban Health and Demographic Surveillance System (NUHDSS) and two cross-sectional household surveys in Korogocho and Viwandani informal settlements in 2004–05 and 2006–08.

Methods Odds of facility-based delivery were estimated before and after introduction of an output-based voucher. Supporting NUHDSS data were used to determine whether any trend in maternal health care was coincident with immunizations, a non-voucher outpatient service. As part of NUHDSS, households in Korogocho and Viwandani reported place of delivery and the presence of a skilled birth attendant (2003–10) and vaccination coverage (2003–09). A detailed maternal and child health (MCH) tool was added to NUHDSS (September 2006–10). Prospective enrolment in NUHDSS-MCH was conditional on having a newborn after September 2006. In addition to recording mother’s place of delivery, NUHDSS-MCH recorded the use of the voucher.

Findings There were significantly greater odds of a facility-based delivery among respondents during the voucher programme compared with similar respondents prior to voucher launch. Testing whether unrelated outpatient care also increased, a falsification exercise found no significant increase in immunizations for children 12–23 months of age in the same period. Although the proportion completing any antenatal care (ANC) visit remained above 95% of all reported pregnancies and there was a significant increase in facility-based deliveries, the proportion of women completing 4+ ANC visits was significantly lower during the voucher programme.

Conclusions A positive association was observed between vouchers and facility-based deliveries in Nairobi. Although there is a need for higher quality evidence and validation in future studies, this statistically significant and policy relevant finding suggests that increases in facility-based deliveries can be achieved through output-based finance models that target subsidies to underserved populations.