The health status of many populations in developing countries have been substantially improved over the past two decades [1]. Despite the progress achieved so far, Millennium Development Goals (MDGs) particularly the goal of reducing maternal and newborn mortality remains underachieved in many sub-Saharan African countries [2]. Equitable maternal and child health services to improve the health of the women and children across their life course are one of the key priorities of Universal Health Coverage (UHC) [3]. Addressing health service inequalities such as the inequalities between the rich and the poor within one country pose a challenge to policy makers [4].

The MDGs measure health achievements based on aggregated measures of progress. This has masked the inequalities in health outcomes that existed between and within countries and among subgroups in a given population [5]. Learning from the MDGs experience, the 2030 agenda for sustainable development has been firmly anchored in the principle of UHC [6], with a strong commitment to equity [7]. In this context, the implementation of Sustainable Development Goals (SDGs) required metrics to measure inclusion and exclusion of specific population groups [5].

Each year hundreds of thousands of women die due to pregnancy and child birth related causes [8]. Given that the risk of maternal death is highest in 24–48 h of the postpartum period, the presence of skilled birth attendant during childbirth is a key intervention for preventing maternal and newborn deaths. In 2012, about 40 million births in developing countries were not attended by skilled health personnel [9].

Inequalities in maternal health have been widely acknowledged, both across countries [9–11] and within countries [12]. The proportion of births delivered by skilled birth attendant has been identified as the maternal health intervention indicator with the most pronounced economic-related inequality [12].

On this subject, over the past decades, Ethiopia has made great efforts to strengthen its health system and improve the health of women. Ethiopia is one of the few African countries that has reached its target in improving maternal health and reducing child mortality [13]. Despite these encouraging achievments, key child and maternal health services were struck with unfair distribution of maternal health service within and across regions, and across population subgroups based on variety of socio-economic variables [14] such as, between richest versus poorest and most educated versus less educated.

Ethiopia has made substantial progress in improving the health of the population by achieving most of the health-related MDGs [15]. Despite rapid and double-digit economic growth over the past two decades, Ethiopia remains one of the poorest countries in the world [16] with 22% of the people living below the income poverty line [17]. Ethiopia is considered as an example for low-income countries to attain MDGs with limited resource coupled with a sustained political will and commitment to provide innovative policies, strategies and programs [18]. However, analyzing improvements through an equity lens reveals that the rapid economic growth has not been enjoyed fairly across the different segments of the population. In addition, the impressive gains in health sector in recent years are unevenly distributed, and aggregated indicators hide striking inequalities across the population subgroups.

For this reason, the Ethiopian Federal Ministry of Health has designed a new plan, the Health Sector Transformation Plan (HSTP) 2015/16–2019/20, to improve health by addressing inequalities [19]. Inequalities in the main socio-economic stratifiers such as poorest versus richest and less educated versus most educated are major contributors to the overall inequalities in the country. The pervasive inequity among its population, particularly between the poorest and the richest, remains the major health sector challenge.

In the perspective of achieving UHC in a country as diverse as Ethiopia, having large social inequalities combined with fast economic growth, it is clear that inequalities must be measured and trends need to be understood. With policy-makers who are increasingly looking at quantitative evidence to make evidence based decision-making to address health inequalities, monitoring equity and measuring the level of health service inequality is of paramount importance. The purpose of this study is therefore to examine level and trend of skilled delivery service coverage, and wealth and education related inequalities associated with receiving the service in Ethiopia during 2000–16.

The present study aimed to examine levels and trends of proportion of births attended by skilled health personnel, and assess economic and education related inequalities using data from a nationally representative survey. It demonstrated how skilled delivery service and socio-economic related inequalities has arisen between 2000 and 16 and revealed which women subgroups are the most underserved.

Findings of the study revealed that proportion of births attended by skilled health personnel was found to be very low in Ethiopia. Other similar studies from Ethiopia [24, 25] also reported that skilled delivery coverage was low, even as compared to Tanzania and other sub-Saharan African countries [26–28]; 5.62% in 2000, 6.3% in 2005, 10.8% in 2011, and 28% in 2016. The demonstrated increament might be attributed by the Health Extension Program (HEP) [29]. The program delivers healthcare services both at the health post and in the community, with strong fous on sustained preventive health actions and increased health awarness [30]. The health extension workers are expected to provide post-abortion care, family planning, antenatal care (ANC), clean delivery attendance and postnatal care. Furthermore, they are responsible for referring women with obstetric complications to health centers and hospitals where basic and comprehensive emergency obstetric care is available. However, other studies [31–33] have shown the incompetencies of HEWs for managing labour and complications and their incapable role in supporting births [33–35].

The observed findings of the study underscored statistically significant levels of socio-economic inequalities in proportion of births attended by skilled health personnel; most importantly, proportion of births attended by skilled health personnelwas observed to be affected by wealth and education characteristics of women.

The association of education and receipt of skilled delivery was consistent. Women who completed secondary and above education were more likely to deliver with assistance of skilled birth attendant when compared to women with no formal education. This result of the current study is also inline with evidences from Ethiopia [24, 35–41] as well as from other sub-Saharan African countries [24, 28, 41–45]. The effect of education on skilled birth attendance can be explained in a range of ways such as either improving income to spend on healthcare or improving attitude and knowledge towards better healthcare service delivery [46]. Education improves women income and ability to afford the cost of healthcare [47, 48]. Better educated women are also considered to have improved knowledge, attitude and practice of skilled maternity services and benefited in using such services [48–51].

Similarly, our findings also give credence that proportion of births attended by skilled health personnel increased with rising economic status. The findings revealed that women in the poorest quintile typically experienced lower levels of skilled delivery service as compared to their richest counterparts. This is in agreement with findings from previous studies from Ethiopia [52] and other parts of the world [53, 54]. This may be due to the reason that even though skilled delivery services are provided freely in Ethiopia, there may be directly and indirectly associated costs that women in the richest quintile can afford [55]. In broad terms, financial capability of the family and costs of a facility delivery including transportation costs may not be afforded by women among poorest quintile. While directly affecting whether a woman can actually reach a facility for delivery (second delay), the anticipation of high costs will affect whether a decision for a facility delivery is made in the first place (first delay) [44]. Overall, the coverage gap among richest vs. poorest women is the greatest unfairness [56] and, confronts with defined goal of UHC “to ensure that all peoples obtain the health services they need without suffering financial hardship when paying for them” [57, 58].

Results from trend analysis verified that the gap in equity in skilled delivery service has worsened and increased linearly across economic status and education levels. Thus, richest and women who completed secondary and above education are the better off subgroups in receiving skilled delivery service. The observed findings from the inequality analysis are in conformity with what is obtainable in previous studies [59–63].

Overall, the evidence we found suggested that towards universal health coverage for skilled delivery services in Ethiopia is still a long way to go. as majority of poorest and uneducated women do not make use of the available skilled delivery services.

Skilled delivery service remained low and has shown small increment in Ethiopia during 2000–2011, but showed substantial increment in 2016. Gap on wealth and education related inequalities increased linearly during 2000–16. Most pronounced inequalities were seen by women level of education revealing women with no formal education were the most underserved subgroups. Encouraging mother’s education and economic development programs geared at improving incomes of women should be strengthened. Further studies should be conducted to assess determinants of skilled delivery service and their relative contribution over socio-economic related inequalities as Ethiopia is looking forward in achieving UHC of Sustainable Development Goals (SDGs).