Community-and proximate-level factors associated with perinatal mortality in Nigeria: evidence from a nationwide household survey

Perinatal mortality (PM) includes foetal death from 22 weeks of gestation (stillbirth) and death within the first week after live birth (early neonatal death) [1]. PM reflects the effectiveness of healthcare provided to mothers and their babies during the antepartum, intrapartum and postpartum periods. It remains a significant global public health issue, particularly in developing countries, where approximately 98% of perinatal deaths occur [1]. A recent global estimate on childhood mortality suggested that approximately 4.8 million perinatal deaths occurred in 2009; of these deaths, 2.6 million were stillbirths while the remainder were early neonatal deaths [2]. These deaths are mostly linked to intrapartum-related stillbirths or newborn deaths; for example, nearly 50% of the 2.6 million stillbirths worldwide occurred in the intrapartum period [2, 3]. Perinatal deaths are preventable with optimal healthcare services, such as adequate receipt of antenatal care during pregnancy, skilled healthcare personnel assistance during labour and delivery, as well as quality care during the postpartum period.

Stillbirths and early neonatal deaths remain unacceptably high in Nigeria. Nigeria currently ranks second globally with nearly half a million stillbirths [4] and third with approximately a quarter million neonatal deaths (0–27 days) [5]. Every year in Nigeria, over 75% of neonatal deaths occur during the early neonatal period (0–6 days) [6]. The 2013 Nigeria Demographic and Health Survey (NDHS) report on childhood mortality indicated a reversal in gains made over previous years in reduction of perinatal mortality rates (PMRs) from 39 to 41 perinatal deaths per 1000 births between 2008 and 2013 [6], indicating a slight increase by 5.1%. Considering this statistic, the Federal Ministry of Health formulated and adopted the Nigeria Every Newborn Action Plan, whose core aims include a strategic plan to significantly reduce preventable newborn deaths and stillbirths in Nigeria by 2030 [7]. This policy initiative lacks comprehensive information on effective ways to treat the health risks experienced by mothers and newborns, such as antepartum bleeding, foetal growth retardation and preterm birth, particularly at the community level where about 66% of births occur at non-healthcare facilities [6, 7]. This is concerning because past studies have shown that antepartum bleeding [8] and foetal growth retardation elevate the risk of PM [9].

Few studies of PM have been conducted [10, 11] in Nigeria, but these studies were all hospital-based with small-scale surveys tailored to fit specific geopolitical populations. These studies indicated that low birth weight, maternal age, low number of antenatal visits, antepartum haemorrhage, prolonged labour, caesarean delivery, multiple gestation, unbooked pregnancies and birth asphyxia were associated with perinatal deaths. Limitations of these studies are that stillbirths and early neonatal deaths that occurred at non-healthcare facilities were not included and their findings may not be generalisable to the wider Nigerian population. Second, environmental factors were not considered in these studies despite the reported relationship between stillbirths and indoor air pollution in earlier studies [12, 13]. Prior to this study, there were no population-based studies assessing PM or population-attributable risk (PAR) estimates adjusted for independent risk factors related to PM in Nigeria.

Accordingly, this study used national household data, which captured every locality and ethnic group in Nigeria, to investigate the community-, socio-economic-, proximate- (or closest maternal, delivery and newborn characteristics) and environmental-level factors associated with PM. We also estimated the adjusted PAR proportions to provide the magnitude of the PM attributable to each significant risk factor in Nigeria. Estimates from this study will greatly assist health and economic policymakers in formulating cost-effective evidence-based national intervention programs to ensure that existing limited healthcare resources are used appropriately to scale down PM across the six geopolitical zones, including rural, metropolitan and urban areas in Nigeria.

The 2013 NDHS cross-sectional household dataset publicly available online was used in this study. Information relating to pregnancies (stillbirths and live births) was detailed by eligible women aged between 15 and 49 years. Approximately 38,948 women were successfully interviewed during the 2013 NDHS survey. The statistical methodology used to report the number of pregnancies was described previously [7]. There were 31,121 pregnancies (weighted total) within the 5-year period (2008–2013).

In the study analysis, stillbirths (≥28 weeks gestation) and singleton early neonatal deaths (0–6 days) were combined and defined as PM. Information regarding perinatal deaths was restricted to the 5-year period to reduce recall errors of birth or death dates by mothers.

There was a weighted total of 1196 perinatal deaths comprising 396 third semester stillbirths (≥28 weeks of gestation) and 800 singleton early neonatal deaths (0–6 days) during the 5-year study period (2008–2013). A greater PMR was observed among newborn babies whose mothers were obese compared with those who had normal weight (PMR: 58 vs 37). Newborn babies delivered through caesarean section (CS) had a higher PMR than those who had a vaginal birth (PMR: 73 vs 25). Similarly, newborn babies perceived by their mothers as small or very small had a higher PMR than those of average or larger size (PMR: 46 vs 21) (Table 1).

Multivariable analyses revealed that babies born to older mothers (age ≥ 40 years) had significant odds of perinatal deaths (adjusted odds ratio (aOR) = 1.35, 95% confidence interval [CI]: 1.06–1.73) compared with those born to mothers aged < 20 or 30–39 years. Babies whose birth size was perceived as small or smaller by their mothers were 1.92 times more likely to die during the perinatal period than those perceived as average or larger in size. Male babies (aOR = 1.45, 95% CI: 1.25–1.68) were also more likely to die during the perinatal period than their female counterparts, as were babies delivered through CS (aOR = 2.85, 95% CI: 2.02–4.02) (Table 2).

Other significant factors that elevated perinatal deaths during the study period were babies born to mothers living in rural areas (aOR = 1.33, 95% CI: 1.11–1.60), babies of a fourth or higher birth order with a birth interval ≤ 2 years (aOR = 1.86, 95% CI: 1.44–2.41), babies of first birth order (aOR = 1.81, 95% CI: 1.43–2.78) and babies of a second or third birth order with a birth interval ≤ 2 years (aOR = 1.76, 95% CI: 1.34–2.31). In addition, babies born to obese mothers were more likely to die (aOR = 1.46, 95% CI: 1.13–1.89) compared with those having low BMI (Table 2).

Between 2008 and 2013, approximately 18% of perinatal deaths in Nigeria were attributed to babies whose mothers reside in rural areas (PAR = 0.176, 95% CI: 0.07–0.28). During the same period, approximately 4% of perinatal deaths were attributed to babies whose mother’s BMI (MBMI) was ≥30 kg/m² (PAR = 0.037, 95% CI: 0.010–0.070). Similarly, around 12% of perinatal deaths were attributed to male babies (PAR = 0.119, 95% CI: 0.070–0.170) (Table 3).

The risk of perinatal death in Nigeria between 2008 and 2013 was significantly elevated by a range of risk factors, including babies born to older women (≥40 years of age), residing in rural areas, male gender, mother being obese (MBMI ≥30 kg/m²), having small or smaller birth size, birth through CS and having a fourth or higher birth order with a short birth interval ≤ 2 years after adjusting for necessary coexisting risk factors, including environmental-level factors.

The limitations of the current study are: (1) It is possible that over- or under-estimation may have affected PM risk estimates identified in this study because characteristics such neonatal jaundice, gestational age, sepsis or congenital anomalies, which were earlier found to be significantly related to early neonatal deaths in various hospital-based studies [10, 11] were not available for investigation. It is also possible that included characteristic such as perceived newborn size at birth by mothers may have impacted PM estimates because the rationale or criteria used was unclear. The perceived newborn size at birth by mothers could be limited by mother’s prior knowledge and experience of newborn. (2) Information on medical risk factors related to mothers during pregnancy, such as diabetes mellitus, hypertension and genitourinary tract infection [19, 20] previously found to be significantly associated with PM were lacking in the 2013 NDHS. (3) It has been argued that using early-pregnancy weight and height measurements yield more accurate BMI [21]; however, the current study assumed that MBMI at the time of survey was the same as that prior to the index birth, which may have biased our findings. (4) The number of newborn deaths and stillbirths may have been under-reported because only surviving mothers were interviewed. Additionally, mothers may have erroneously reported the gestational age when they had a stillbirth.

Notwithstanding these aforementioned weaknesses, this study used a nationally representative sample compared with earlier hospital-based studies in Nigeria [10, 11]. More importantly, this study suggested country-wide evidence on primary key factors associated with PM, which will enable healthcare policymakers to formulate uniform intervention programs to improve child survival across all six geopolitical zones and the Federal Capital Territory of Nigeria. In addition, we explored more data on many possible coexisting risk factors related to PM, including environmental-level factors, for sufficient statistical control.

Babies born to obese mothers had a 1.46 times greater risk of dying in the perinatal period than those having normal MBMI (18.5 ≤ MBMI ≤24.9). Similar findings were reported in earlier studies conducted in both developing and developed countries Nigeria [22], sub-Saharan Africa [23], Russia [24] and Sweden [25]. An increased likelihood of perinatal deaths for babies born to obese mothers may be attributed to undiagnosed diabetes, gestational diabetes or prediabetic hyperglycaemia, hypertension and large-for-gestational-age birth, which were previously found to be associated with foetal or newborn deaths [26]. This is supported by observational studies on maternal obese and pregnancy outcome in Nigeria, which found that diabetes mellitus, birth asphyxia, hypertensive disorders and macrosomia were significant medical risk factors associated with pregnant obese mothers in Nigeria [27]. Another possible reason for the elevated perinatal deaths among obese mothers may be because they are ineffective at recognising decreased foetal movement, which often leads to foetal demise compared with underweight or normal weight mothers [28]. The impact of obesity remains a crucial and amendable risk factor for PM. Effective maternal weight loss or control in obese women during pregnancy has been reported to reduce gestational diabetes, large-for-gestational-age birth and neonatal mortality [29].

The odds of perinatal deaths were greater in older mothers aged 40 years or higher compared with younger mothers. This finding is in contrast with earlier studies in Russia and Bangladesh [19, 30], which showed a statistically insignificant relationship between older mothers and perinatal deaths. A plausible explanation for these differing outcomes may be attributed to different definitions of PM, different populations, adjusted for different risk factors and the maternal age limits used. Nevertheless, other reports from both developing and developed countries also indicated that older mothers had a significantly elevated risk of perinatal death [31, 32]. The significantly increased perinatal deaths associated with older Nigeria mothers could be related to medical risk factors, such as antepartum haemorrhage, hypertension, operative vaginal delivery and gestational diabetes, which were previously reported to be associated with advanced maternal age [8, 26].

Babies perceived as small size after birth by their mothers remain a significant public health problem in Nigeria. A recent Nigerian population-based study suggested that nearly 30,000 newborn deaths in their first week of life were attributable to small-sized babies [15]. The current study provides further evidence that smaller-than-average babies is a strong predictor of perinatal death in Nigeria, which is consistent with findings from previous studies [15, 33]. A plausible reason for the increased risk of perinatal deaths among the small-sized babies in Nigeria may be attributed to use of herbal medicines not prescribed [34] and poor diet intake during pregnancy often impact the foetus.

Furthermore, studies in low- and middle-income countries [35, 36] have reported that babies born to mothers residing in rural residences are more likely to experience PM compared with those in urban areas, and this study reaffirms the strong effects of rural residence on perinatal deaths. This may be due to inadequate access to healthcare facilities and maternal healthcare services. Most of the well-equipped hospitals and healthcare centres in Nigeria are typically found in urban and metropolitan areas, leading to a lower likelihood of perinatal deaths in urban areas. The risk of perinatal death was significantly greater for male babies than for female babies. This may be attributed to biological factors [37], such as late development of foetal lung in the first 7 days of life [38], resulting in more frequent respiratory diseases in male babies than in female babies.

Babies delivered by CS exhibited an almost threefold risk of perinatal death compared with vaginally born babies, which contradicts a previous study conducted in Swaziland [39]. However, our result is consistent with a similar study performed in Mexico [40]. An increased risk of CS may be linked to negative perceptions (e.g., fear, aversion) to CS [41] among pregnant women in Nigeria, which often leads to late referral to healthcare facilities for emergency CS after experiencing life-threatening complications at home or elsewhere. We also observed that babies of high birth order (fourth or higher) born with shorter birth intervals (≤2 years) had greater odds of dying during the perinatal period. This outcome is in line with an earlier study conducted in Kenya [42], which may be partly attributed to economic resource competition among infants and maternal depletion syndrome [43].

To accelerate progress towards reducing prenatal mortality in Nigeria by 2030, public health interventions are needed at the community and individual level. At the community level intervention, screening programmes during pregnancy should be encouraged among older mothers especially those who live in rural areas, At the individual level intervention, educating mothers on kangaroo mother care approach on small-sized or low birth weight newborns including those delievered by caesarean section. However, to achieve these goals, the political, economic and social obligation of the three tiers of government (Federal, State, and Local Goverment Area) are very important to substantially reduce perinatal deaths.

This finding suggests that newborn care interventions are urgently needed, at the community and individual level that aim to educate mothers on the benefits of weight loss or control, kangaroo mother care of small-sized babies, child spacing, timely referral for unwell babies, planned or elective CS, and promote regular medical monitoring of older pregnant mothers. These interventions will remarkably improve the rate of PM in Nigeria.