This study represents the first-ever assessment of state-level trends for a range of MCH interventions and outcomes in Nigeria, highlighting the country’s mixture of progress and ongoing challenges in improving local health service provision. Every state recorded declines in under-5 mortality – a major success – yet, absolute rates of child deaths still ranked among the highest in sub-Saharan Africa [2]. For a subset of malaria interventions, coverage increased substantially between 2009 and 2013; however, coverage remained quite low, particularly for IPTp2 and ACTs, a cause for concern given Nigeria’s large malaria burden [4]. Coverage of certain immunizations increased, especially for OPV3, an important result given Nigeria’s aims to end wild polio transmission [56]. At the same time, similar gains were not actualized for DPT3 coverage across states, suggesting that more routine delivery platforms for multi-dose vaccines may be faltering amid disease-focused immunization campaigns [40, 58]. Coverage of other key MCH interventions, such as ANC4 and SBA, generally stagnated or declined, and stark differences in coverage have persisted across states since 2000. Benchmarking state-level performance for MCH indicators demonstrated the continued entrenchment of North-South differences, particularly for more routine services, and showed that overall intervention coverage generally remained low despite recent gains for a subset of MCH interventions.

Nigeria’s state-level trends in under-5 mortality likely reflect the complex nature of improving health outcomes amid local changes in health system access, delivery of services, broader socio-economic gains, and overall development. While all states experienced reductions in under-5 mortality between 2000 and 2013, it is unlikely that these gains were driven by the same factors in each state. In states where malaria transmission is particularly high and coverage of ITNs increased, such as Bauchi, improved childhood survival may be attributable to expanded malaria control programming. In contrast, in urban areas where malaria transmission is somewhat lower and women’s educational attainment rose since 2000, such as Edo, socio-economic advances may play a stronger role in reducing under-5 deaths. Assessing how different intervention packages and socio-economic forces are contributing the largest gains in childhood survival – and doing so at local levels – is critical to accelerating improved health throughout Nigeria. For disease-specific programs that feature well-funded, focused campaigns (namely malaria and polio) [5–7], the scale-up of intervention coverage was less varied across states. For instance, by 2013, many states in more rural, poor areas reached levels of OPV3 coverage found in the wealthier states of Nigeria. Although absolute levels of immunization coverage remained lower than optimal, the gap between states with the highest and lowest levels of coverage narrowed over time. Conversely, inequalities in the coverage of several MCH interventions and services provided through more routine platforms continued across states, often following geographic patterns for urbanicity, wealth, and educational attainment [32, 59]. These findings suggest that barriers to accessing and using health services likely remain in many states, particularly those in more remote, impoverished areas. These factors involve ongoing violence in northern Nigeria [60–62]; demand-side influences (proximity to facilities and care [63–65], affordability of transportation to health facilities [66], cost of health care [67], knowledge of available services and trust in providers [28], religious views or cultural mores [68, 69]); and supply-side dynamics (availability of skilled medical staff and their interactions with patients [70–72], inconsistent stocks of pharmaceuticals and medical supplies across levels of care [73–75], inadequate facility infrastructure [76]). In combination, these factors may have a compounding effect on hindering health-care-seeking behaviors. Additional work on identifying which of these factors are most easily affected by policy levers and programs promoting heighted utilization of routine services in Nigeria should be prioritized.

Nigeria’s gains in improving polio immunization coverage, particularly when compared to trends in DPT3 vaccination rates, highlight the differences in the country’s health system functions across specific interventions. As one of the last polio-endemic countries in the world, Nigeria has received tremendous resources and policy attention for eliminating polio, especially through the GPEI [56, 77]. Due to targeted immunization campaigns and developing disease surveillance structures [56, 78, 79], Nigeria increased OPV3 immunization coverage by 25 percentage points since 2000 and created a strong detection-response system for finding its remaining polio cases. Such progress is particularly impressive given that Nigeria has experienced tensions and violence around polio vaccination, notably culminating in boycotts of immunization campaigns in Kano, Zamfara, and Kaduna in 2003 and 2004 [80, 81], and multiple shootings in 2013 [82]. On the contrary, Nigeria saw minimal progress for DPT3 immunization rates, another three-dose vaccine that is delivered through more routine EPI services rather than mass campaigns. This contrast with Nigeria’s gains in OPV3 coverage reflects how program-focused investments and commitment can likely improve vaccination rates, as well as possible missed opportunities for integrating service delivery [55, 58].

Diverging state-level trends for MCH interventions revealed geographic disparities along a continuum of care for maternal health services. In a health system where both demand and supply for health services are strong, we might expect to see similar coverage levels for ANC1, ANC4, SBA, and IFD, or that women have least four ANC visits prior to delivery and give birth in a health facility and/or in the presence of skilled attendant [83]. We found that a subset of states, largely located in the southern regions of Nigeria, appeared to have strong linkages between these services, experiencing minimal differences in coverage for ANC1 and ANC4, for example. However, the majority of states saw some kind of breakdown in this MCH service continuum. These findings point to two related but separate challenges to bolstering Nigeria’s continuum of care for MCH services: (1) improving the frequency of ANC visits and (2) cultivating stronger demand and capacity for giving birth with skilled birth attendants or in health facilities. Previous research has identified cost, transportation, and capacity of the health facility as barriers for women seeking ANC services [84, 85] and SBA [14, 86, 87]. Local health authorities may consider expanding and scaling up existing programs which include outreach campaigns, improving facility-based resources for ANC and routine deliveries, and innovative incentive structures, such as conditional cash transfers, that explicitly link ANC to post-natal services [1, 14, 16, 88–91].

This study further demonstrates the importance of setting ambitious yet realistic health system goals, as well as approaching such target-setting with an equity lens. Nigeria established several high-reaching health program goals to improve MCH outcomes, which included achieving 80% ITN coverage by 2013 [92], 78% DPT3 coverage by 2013 [54], and rates of 38% for EBF by 2013 [10]. We found that national coverage of these interventions – 47% for ITN ownership, 46% for DPT3, and 15% for EBF – registered well below the country’s targets in 2013. While a few states met or exceeded these targets for EBF and DPT3 (e.g., Osun and Ekiti had EBF rates exceeding 40% in 2013), most states fell quite short of the country’s health program goals. Many of these targets may have been overly ambitious given baseline levels of intervention coverage (e.g., at 14% ITN ownership in 2009, Nigeria remained 66 percentage points away from its goal of 80% in 2013); at the same time, Nigeria’s goals align with global recommendations and targets for improving priority MCH outcomes (e.g. the MDGs). To accelerate Nigeria’s progress toward its health system goals for 2015 and beyond, a heightened focus on the country’s most disadvantaged populations will be required. EBF, for example, is considered highly cost-effective for improving childhood survival, requires minimal investments in health system infrastructure to scale up, and has been expanded rapidly in other African countries [42]; thus, strengthening educational outreach about EBF [93] and expanding facility-based breastfeeding programs, such as the Baby Friendly Hospital Initiative [94], across levels of care may promote better child health outcomes in states with low levels of EBF. Without a greater focus on local health needs and addressing Nigeria’s persistent health inequalities, the gaps between states with the highest and lowest levels of intervention coverage will likely widen over time. This finding also emphasizes the need for incorporating explicit equity goals within the next generation of international target-setting with the Sustainable Development Goals [95].

Our findings correspond with recent policy developments in Nigeria, namely the National Health Bill’s enactment in December 2014 [17]. This bill aims to address many of the MCH indicators analyzed in our study, with leadership claiming that its effective implementation will save over 3 million “lives of mothers, newborns, and under-5’s by 2022” [96]. The National Health Bill’s success hinges upon successful execution throughout Nigeria, a feat that has challenged the country’s past health reforms [11, 12, 97]. The use of subnational benchmarking to monitor indicators related to the National Health Bill will be critical for tracking local progress, promptly identifying obstacles in implementation, and building local accountability mechanisms. These efforts may be further improved by strengthening local health information systems, namely Nigeria’s District Health Information System (DHIS2) [98], and expanding the types of indicators captured by these systems (e.g. data pertaining to non-communicable diseases).