Background
There is growing focus on improving maternal-perinatal survival through health system strengthening (HSS). Despite such efforts, facility birth coverage often remains low in low-income settings. We explored factors influencing facility birth utilization during a national HSS initiative in rural Guinea-Bissau.

Methods
Using an explanatory sequential mixed-methods approach nested in the Bandim Health Project’s rural Health and Demographic Surveillance System (HDSS), we conducted 258 structured and 12 in-depth interviews with women who had recently given birth. Data were analysed using descriptive statistics and thematic network analysis guided by theories of social practice.

Findings
In the structured interviews, most women reported that they had planned a facility birth (171/258, 66 %), and 28 % reported access barriers (73/258). However, only half of the interviewed women actually gave birth at a health facility (128/258, 50 %), suggesting that facility births frequently remained unattainable. In the in-depth interviews, women described multiple “prerequisites” that needed to be met to access facility births such as financial means for out-of-pocket payments (OOPs). Despite official user fee waivers, OOPs were reported by 71 % of the structured-interview participants with facility births (91/128) but only three of these women referred to OOPs as barriers.

Conclusions
Our findings suggest that the women do not feel entitled to free-of-charge facility births, which may explain underreporting of financial barriers. Ubiquitous OOPs are further suggestive of ‘commodification’ of facility births, such that individual ability to pay remains key to utilization. Our findings raise equity concerns and call for closer monitoring of the implementation of HSS initiatives.