Prevalence, Trends, and Factors Associated with Teen Motherhood in Nigeria: An Analysis of the 2008–2018 Nigeria Demographic and Health Surveys

Abstract Background: Teen pregnancy and childbearing are common in Nigeria, and understanding the complexities, such as sociodemographics and economic factors including sexual and reproductive health knowledge and awareness among adolescents over time can trigger innovative approaches and interventions. This study intends to capture the patterns and associated factors of teen motherhood among sexually active adolescents (15–19 years) between 2008 and 2018. Methods: The study data was extracted from 2008, 2013, and 2018 Nigeria Demographic and Health Surveys. Descriptive analysis was presented using frequencies and percentages; multivariable analysis was conducted using log-binomial logistic regression at a p-value <0.05. All analyses were performed using Stata 15.0, weighted and adjusted for the complex survey design and population size. Results: The prevalence of teen motherhood increased between the three successive survey waves (50.9% vs. 52.4% vs. 55.2%) from 2008, 2013, and 2018. Although, the pooled adjusted analysis revealed no significant change over the 10-year period. Knowledge of modern contraceptive methods, primary education, non-Catholic Christians, residing in the South-South region, and those currently or formerly married were associated with increased risk of teen motherhood. There was an inverse relationship between teen motherhood and wealth status; lower wealth status was associated with high adolescent pregnancy and childbearing. Conclusion: This study revealed an increase in the proportion of teen pregnancy and childbearing in Nigeria. Notably, there exist variations across age groups, geographic location, educational level, religious belief, marital and economic status. Interventions that ensure comprehensive sexuality education, girl child education, and economic empowerment especially for school dropouts are advocated to reduce teen motherhood.


Introduction
Teenage pregnancy and childbirth is a global public health concern posing serious threats to the health and the general well-being of teenagers (UNFPA, 2017). In the developed world, the associations between teenage births and mortality, morbidity, and social and economic hardship for the mother and child are well established (Skinner & Marino, 2016) as teen pregnancy is a major indicator of adolescent health including mental, social and economic well-being of adolescents (Hindin et al., 2016). Research over many decades has provided a good understanding of the underlying factors for the complex issue of teenage pregnancy and reasonable evidence of what strategies work to limit it (Watts et al., 2018). The situation of teen pregnancies in developing world is quite precarious as evident by a study conducted in India which showed that teenage pregnancies are still a common occurrence in rural idea although there are various legislation and government programmes to mitigate the risk factor for poor obstetric outcome (Mahavarkar et al., 2008).
Cultural practices, poor socioeconomic conditions, low literacy rate, and lack of awareness of the risks are some of the main contributory factors identified as drivers for teen pregnancies in most developing countries in Africa (Ochen et al., 2019). Teenage pregnancy and childbirth and their associated challenges are disproportionately endemic in low-and-middle income countries (LMICs) and remain the leading cause of death among adolescents aged 15-19 years (Neal et al., 2012). While the global adolescent fertility rate is gradually declining, the number of childbirths to adolescents 15-19 years has increased (Ganchimeg et al., 2014;WHO, 2020). West Africa accounts for the highest proportion of childbirths to adolescents after East Asia, partly due to the increasing population of female adolescents in these regions (Every Woman Every Child, 2015;Ganchimeg et al., 2014;UN DESA, 2017;UNFPA, 2013;WHO, 2020). It is forecasted that by 2030, Nigeria will have the highest population of adolescent girls between the ages of 10 and 17 (UNFPA, 2013).
Each year, adolescent girls aged 15-19 in LMICs record an estimated 21 million pregnancies, nearly half of which-10 million are unintended while just more than a quarter-an estimated 5.7 million ends in abortion, the majority of which occur in unsafe condition. This translates to an estimated 20,000 girls under the age of 18 giving birth each day (UNFPA, 2017(UNFPA, , 2022. Also, these pregnancies are associated with adverse obstetric and perinatal outcomes, such as episiotomy, puerperal endometritis, premature delivery, postpartum hemorrhage, preterm delivery, obstructed labor, low birth weight, and perinatal death (Abebe et al., 2020;Kirbas et al., 2016;UNFPA, 2022;Zhirudin et al., 2017).
Several factors account for the prevalence of teenage pregnancy, some of these factors include rural-urban differentials, poor socioeconomic status, early onset of menarche, peer pressure, limited education, poor reproductive health knowledge, and unsafe sexual practices (Akombi-Inyang et al., 2022;Cook & Cameron, 2017;Francis Fagbamigbe et al., 2019;Institute, 2016) Teenage girls often engage in unsafe behaviors just to conform to widely held societal stereotypes of what is deemed attractive by the opposite sex (Kågesten et al., 2016;Rudman & Glick, 2021). Also, prior research has shown that teenagers have poor knowledge of birth control measures due to the cultural inappropriateness of sex education in many places of the world (Miller, 2002). Cultural conflict with sexuality education in Nigerian has also been pointed out (Fakeye, 2014;Mukoro, 2017a). Hence, the need for sexuality education initiatives to be harmonized within the context of socio-cultural values in Nigeria cannot be overemphasized.
Higher levels of teenage pregnancies are recorded in rural areas compared to urban settings and among girls from poor socioeconomic backgrounds (Ajala, 2014;Francis Fagbamigbe et al., 2019;Institute, 2016). The ability of teen mothers to navigate through motherhood successfully can contribute positively toward their overall sexual health. Sexual health is essential to one's overall health and well-being as reinforced by the World Health Organization (WHO, 2023). Sexual health education targeting teenagers help to draw teenagers' attention to some safe sex practices as well as risky sexual activities and their consequences (CDC, 2020). Such education can also help the teenagers to live sexual lives that will reduce their chances of perpetrating risky sexual activities, such as condom discontinuation (Jemisenia et al., 2021) and early initiation of sex (Tenkorang et al., 2014).
In Nigeria, the adolescent fertility rate of 102 live births per 1,000 in 2020 was the highest in Africa and the growing size of the youthful population is likely to escalate an already worsening situation of maternal and child health outcomes as a result of increased teenage pregnancies (Bank, 2020;UNFPA, 2013;WHO, 2019). This makes teenage pregnancies and births a major public health concern in Nigeria and the Federal Government has taken drastic steps to control this public health menace. For instance, to improve access to family planning and reproductive health services, the Federal Government allocated $3 million for the procurement of reproductive health commodities in 2015 with an additional annual commitment of $8.35 million proceeding the next four years following 2015, while UNFPA has supported the government of Nigeria with about $75 million between 2011 and 2022 toward reproductive health commodities procurement and supply. Sex education has recently been removed from the Basic Education curriculum in Nigeria (Sunday, 2022). Justification for this included the fact that Nigeria is a religious country where values and morals are taught in churches and mosques, hence matters of sex education should be left with parents and religious leaders instead of teachers (Sunday, 2022). The legal age of sexual initiation in Nigeria is age 18 and child marriage occurs when one is married before age of 18 (Jerome Amir Singh & Jogee, 2018). Relatedly, there is a need for reforms in the existing social norms to accommodate sex education (Mukoro, 2017b). This could form part of the core values instilled in boys and girls so that they will grow to appreciate and internalize the essence of sexuality and navigate their sex life safely.
However, it remains unclear how these efforts aimed at controlling teenage pregnancy and childbirth in Nigeria are impacting the rate of teenage pregnancies and childbirth over time. Specifically, very little is known about the trend and factors associated with teen pregnancy and childbearing. Such knowledge is necessary to help policymakers and public health practitioners assess, directly or indirectly, the progress of the country in these very crucial outcomes of sexual and reproductive health after several years of targeted preventive interventions by the Federal Government. It will also help development partners to determine drivers and prime locations of teen pregnancy and childbearing thereby strengthening control efforts. The authors, therefore, examined the patterns and associated factors of adolescents' pregnancy and childbearing between 2008 and 2018 in Nigeria.

Data source and sampling procedure
The data used for this study was extracted from 2008, 2013, and the most recent (2018) Nigeria Demographic and Health Surveys (NDHS). These three survey rounds were utilized to ascertain the patterns of pregnancy and childbearing among sexually active adolescents over the 10-years period as well as factors associated with this event. The Demographic and Health Survey (DHS) usually collects data that are comparable across several survey waves to provide information on the country's demographic and health indicators, and these data are used to inform policies, monitor the progress and impact of programmes. The DHS adopts a multi-stage stratified cluster sampling. The first stage involves the selection of enumeration areas after the stratification of the country into urban and rural. Then, the next stage involved the selection of respondents from the selected households. Before pooling the datasets from the three DHS rounds, we denormalized the weight and adjusted for the population size of the adolescents for the different surveys using the World Bank Staff Estimates (Ajakaye & Ibukunoluwa, 2020). The total sample size of the pooled datasets was 9,106 adolescents and these included 2954, 3199, and 2953 adolescents from 2008, 2013, and 2018 NDHS, respectively.

Outcome variable
This study captured the number of sexually active adolescents with either childbirth experience, are currently pregnant or have had a terminated pregnancy. As a result, the following was extracted from the three surveys: (1) number of children ever born (2) currently pregnant, and (3) ever had a terminated pregnancy. In this study, adolescents who had at least a childbirth and/or are currently pregnant and/or ever had a terminated pregnancy were classified as teen motherhood. For the purpose of analysis, adolescents who have never had a terminated pregnancy, were not currently pregnant and never experienced childbirth were coded as 0 whereas any adolescent with any of these experiences was coded as 1.

Explanatory variable
The explanatory variables were: (1) survey rounds-2008, 2013, and 2018 (2) sexual and socio-demographic variables which include-age at first sex classified as (<15, 15-17, and 18-19), number of lifetime sexual partners (single vs. multiple), marital union (never, currently and formerly in a union), level of education (none, primary, secondary, and tertiary), wealth quintile (poorest, poorer, middle, richer and richest) and religion (Catholic, other Christians, Islam, and others) (3) Geographic characteristics-region (North Central, North East, North West, South East, South South, and South West), place of residence (urban and rural), ethnicity (Fulani, Hausa, Igbo, Yoruba, 0 and other ethnic communities) and (4) knowledge and awareness-ever heard of STI (yes and no), knowledge of any contraceptive method (knows none, knows only folkloric or traditional method, knows modern method), comprehensive knowledge about HIV (yes and no) and exposure to mass media (yes and no).
The comprehensive knowledge about HIV was computed using five questions-(I) knowledge about the consistent use of condoms during sexual intercourse, (II) knowing that having only one uninfected faithful partner can reduce the chances of getting HIV, and (III) knowing that a healthy-looking person can have HIV positive, and rejecting the two most common local misconceptions about transmission or prevention of HIV, that (IV) one can be infected by HIV through mosquito bites or (V) by sharing foods with a person infected with AIDS. All respondents who answered correctly to all these questions were said to have comprehensive knowledge about HIV. Also, we measured exposure to mass media using three questions-frequency of listening to the radio, watching television, and reading newspapers or magazines. Respondents without access to any of these three sources were referred to as not having access to mass media while those who had access to any of these sources less than once a week or at least once a week were classified as having access to mass media.

Descriptive and inferential analysis
The percentage and frequency distribution of teen motherhood and sexual, demographic, geographic, awareness, and knowledge of sexual and reproductive health characteristics of the respondents were computed for each of the three survey waves and also for the pooled years (2008, 2013, and 2018). Similarly, the prevalence of teen motherhood by respondents' background characteristics was computed for each of the three survey waves and also for the pooled datasets. We further presented the prevalence of teen motherhood by states within the 10 years of study using the spatial map. Also, collinearity among variables was inspected for the pooled datasets using the variance inflation factor [Mean VIF ¼ 1.59; Minimum ¼ 1.11 and Maximum ¼ 2.99], and no multicollinearity issues were observed. The log-binomial regression was used to compute crude and adjusted relative risk of the association between teen motherhood and the sociodemographic, economic, sexual and reproductive health, knowledge, and awareness factors. Similarly, we modeled the likelihood of each of the outcome variables (currently pregnant, had terminated pregnancy, and childbirth experience) with the selected risk factors.

Descriptive results
The descriptive statistics of the adolescents' sexual, demographic, geographic, awareness, and knowledge of sexual and reproductive health were presented in Table 1. More than half of the adolescents in the survey have had a motherhood experience (about four in 10 adolescents have had a childbirth experience, almost one in 10 are currently pregnant and one in 20 have had a terminated pregnancysee Figure 1) in the three survey rounds. Almost three in 10 adolescents initiated sex before age 15, while three in five were currently in a union and one in 10 adolescents had multiple sexual partners. A higher proportion of the adolescents (45.8%) had no education, were Muslims (60.4%), from the Northwestern region (37%), belonged to the Hausa ethnic group (35.3%), and resided in rural areas (73.4%). More than half of the respondents were in the poorest and poorer wealth quintiles. About one in four had no knowledge of any contraceptive methods, seven in 10 had no comprehensive knowledge about HIV and two in five had no exposure to mass media.
The trends in the prevalence of teen motherhood for the three survey waves were presented in Table 2. The prevalence of teen motherhood increased from 50.9% in 2008 to 52.4% in 2013 and 55.2% in 2018. Teen motherhood was highest among adolescents who initiated sex before age 15 compared to those who initiated sex at a latter age. Almost seven in 10 adolescents who were currently or formerly in a union had pregnancy or childbirth experience. Teen motherhood was highest among those with no education or primary education (almost seven in 10 adolescents) compared to those with secondary or higher education. There was an inverse relationship between teen motherhood and wealth status; lower wealth status was associated with a high adolescent pregnancy and childbearing. Almost seven in 10 of adolescents in the North East and North West region, and Hausa's or Fulani's' as well as those with no exposure to mass media have had a pregnancy or childbirth experience. Also, six in 10 adolescents residing in rural areas had been exposed to pregnancy and childbearing. The geographical distribution of teen motherhood across the states is shown in Figure 2; the Northern region had the highest prevalence of teen motherhood between 2008 and 2018. Almost seven in 10 adolescents residing in Bauchi and Gombe state in the Northeastern region, as well as Katsina and Kaduna in the Northwestern region including Niger in the Northcentral region had experienced teen motherhood while Lagos state (P ¼ 17.4%; 95%CI: 11.7-25.0) has the lowest prevalence of teen motherhood in Nigeria.

Inferential analysis
The pooled crude and adjusted log-binomial regression analysis of the factors associated with teen motherhood was presented in Table 3. Also, we presented the pooled crude analysis of each event, that is; adolescent experience of a terminated pregnancy, currently pregnant, and childbearing in Supplementary Table 1, and their  pooled adjusted analysis in Supplementary Table  2. For this section, we present only the findings from the adjusted model of the factors associated with teen motherhood.
The adjusted analysis from the pooled datasets revealed no significant difference in teen motherhood between the three survey years. The early sexual debut was associated with a higher risk of teen motherhood; those who initiated sex between 15-17 and 18 years older were 14 and 41% less likely to experience teen motherhood. Adolescents with primary education (aRR 1.07; 95%CI 1.02-1.13) were at higher risk while those with a tertiary education (aRR 0.44; 95%CI 0.25-0.78) were less likely to experience teen motherhood compared to those with no formal education. Similarly, adolescents in the richest wealth quintile were 27% less likely to experience teen motherhood compared to those in the poorest group. Being married (aRR 5.30; 95%CI 4.80-5.86) or formerly married (aRR 4.38; 95%CI 3.77-5.10) was associated with a higher risk of teen motherhood.
Also, adolescents who belonged to other Christian groups (aRR 1.18; 95%CI 1.06-1.31) as well as those who belonged to other religions (aRR 1.29; 95%CI 1.10-1.52) were more likely to experience teen motherhood compared to Catholics. Adolescents who resided in the North western region (aRR 0.91; 95%CI 0.83-0.99) had a lower likelihood while those in the South South (aRR 1.15; 95%CI 1.04-1.27) had a higher likelihood of experiencing teen motherhood compared to those in the North central region. Similarly, Hausas were 7% more likely to experience teen motherhood compared to the Fulanis'. Also, those with knowledge about modern contraceptive methods (aRR 1.23; 95%CI 1.16-1.30) were associated with a higher risk of teen motherhood compared to those who knew no contraceptive methods in the adjusted model.

Discussion
Teen motherhood is a global public health and social concern, due to its enormous short and long-term socio-economic and developmental repercussions. According to the 2022 UNFPA report-Motherhood in Childhood: The Untold Story; after the birth of a first child, additional childbearing in adolescence is common for child mothers. Among girls with a first birth at age 14 or younger, nearly three-quarters also have a second birth in adolescence, and 40% of those with two births progress to a third birth before existing adolescence (UNFPA, 2022). The phenomenon of teenage pregnancy is quite alarming in Nigeria, the most populous country in Africa (Senaviratna & Cooray, 2019). The present study, therefore, investigated the spatial distribution and factors associated with teen motherhood in Nigeria, between 2008 and 2018. Within this period, the prevalence of teen motherhood increased from 50.9% in 2008 to 55.2% in 2018. Adolescents with primary education were at higher risk of motherhood while those with a tertiary education were less likely to experience it compared to those who had no formal education.
Our findings affirm previous studies that linked no education and low educational attainment to early motherhood (Kunnuji et al., 2018;Nahar & Zahangir, 2013;Raneri & Wiemann, 2007;Rowlands, 2010). When a girl drops out of school at the primary level, she eventually joins her colleagues who are out of school and jointly gets exposed to a wide array of circumstances leading to childbearing, such as early marriage, cohabiting, and prostitution (Stoner et al., 2019). Although our study design does not offer much insight into temporal sequence and how low level or no education directly influences teen motherhood, it suggests that education has enormous importance on the timing of motherhood. Irrespective of teenagers' education level, intensification of sexual health education and interventions through the various media platforms and cell phones can improve the situation. The use of cell phones and media for sexual education may  be easier, have wider coverage, and greater impact due to the surge in the use of these platforms, especially smart phones, in recent times (Adedeji et al., 2021). Adolescents in the richest wealth quintile were 27% less likely to experience motherhood compared to the poorest adolescents. This is in consonance with some previous studies from Nigeria (Akanbi et al., 2021;Izugbara, 2015) and other parts of sub-Saharan Africa (Ahinkorah et al., 2021;Chirwa et al., 2019). A couple of factors may explain why wealth serves as a protective factor against adolescent motherhood. Wealth facilitates healthcare access since wealthy teenagers can access different varieties of and preferred reproductive health services and ascertain relevant knowledge relative to the poor, thereby reducing their chances of being at risk of teen motherhood (Casey & Lindhorst, 2009). The pathway from teen motherhood to later life outcomes has received considerable attention in both research and political agenda, yet very few studies have however looked beyond educational and economic outcomes including poverty levels among this population (Anakpo & Kollamparambil, 2019). Evidence indicates that poverty and some cultural enhances teen motherhood (Ahinkorah et al., 2019;Garwood et al., 2015). This results from the fact that poor teenagers may depend on others for some basic necessities and tend to have limited bargaining power, hence making them susceptible to unplanned and protected sex thereby leading to pregnancy and motherhood (Chirwa et al., 2019).
Those who were currently or formerly married were associated with a higher risk of childbearing. Childbearing outside marriage is usually treated with disdain, especially when the mother is a teenager (Madhavan et al., 2013;Sennott et al., 2016). As a result, it is expected that teenagers who have ever married will have an increased prospect of being married and giving birth. Unfortunately, the proportion of females in Nigeria who enter marriage before adulthood is on the increase, as also noted from some other countries in sub-Saharan Africa (Avogo & Somefun, 2019;Koski et al., 2017). Our finding confirms earlier reports from Nigeria that young females in marital unions have an increased risk of being pregnant and giving birth (Kunnuji et al., 2018) as also reported from other parts of the world, such as Sweden (Holland, 2013), India (Goli et al., 2015), and Ethiopia (Alemayehu et al., 2010). A critical implication of this finding is that national, regional, and local level interventions that seek to subsidize adolescent motherhood experiences and healthcare services need to prioritize measures that would make adolescent marital unions less attractive and less rewarding. One way to achieve this is to intensify existing human rights laws that prohibit early or forced child (under 18) marriage and the application of associated sanctions.
Other Christians and affiliates of other religions reported higher propensity of motherhood relative to Catholics. This may be linked to doctrinal variations within the Christian religion as well as the different beliefs held by adolescents of other religions. This finding is quite intriguing on the account that Catholicism do not support the use of contraception as an option of birth control, irrespective of the outcome, and only permits natural birth control methods (Ignaciuk & Kelly, 2020). Other studies have shown that non-Catholics do not use contraceptive methods appropriately, partly due to poor knowledge and misconceptions (Ezenwaka et al., 2020;WHO, 2020).
Residents of the North western region had lower likelihood while those in the South South had a higher likelihood of experiencing teen motherhood compared to those in the North central region. Similarly, the Hausas' were 7% more likely to experience teen motherhood compared to the Fulanis'. In some related studies, however, early motherhood was profound among those in the Northern parts of Nigeria (Kunnuji et al., 2018;Rosen et al., 2004). Our findings highlight heterogeneity among Nigerian adolescents and specifically point to geographical and ethnic variation in teen motherhood. Besides, the findings have revealed the category of teens that require more focused anti-motherhood public health interventions in Nigeria.
We also noted that knowledge about modern contraceptive methods was associated with a higher risk of teen motherhood. This casts doubts about the content of the knowledge possessed by these teens as to whether they have the right knowledge or otherwise. Secondly, the finding may imply that possession of contraception knowledge does not necessarily guarantee knowledge application. It could also be that there is a knowledge gap about contraception coupled with misconceptions held by these adolescents as earlier reported by the WHO (WHO, 2020). Studies have shown that adequate contraceptive knowledge does not translate to a high rate of contraceptive use (Somba et al., 2014;Sweya et al., 2016). Besides, poor contraception knowledge has been reported from six communities in southeastern Nigeria, specifically Ebonyi state (Ezenwaka et al., 2020).
The findings possibly suggest the need for modification in current sexuality interventions. Thus, it may be worthwhile to extending existing interventions to cover some positive aspects of sexuality and sexuality development across the life course (Sladden et al., 2021). For instance, pleasure enhancement interventions, such as the Pleasure Project was able to increase the visibility of sexual health, pleasure concepts, and rights (Ford et al., 2021;Philpott et al., 2021). Besides, an exploration of the protection, promotion, and maintenance of rights, sexual as well as pleasure through the life course may also be helpful (Sladden et al., 2021).

Strengths and limitations
This study has several strengths as well as limitations. One of the major strengths is that the sampling procedure ensured representativeness, thereby making the findings and conclusions representative of Nigerian adolescents, within the period studied. Secondly, the study was based on pooled data from three consecutive survey rounds and we adjusted for the population of adolescents for the three different time points before pooling the datasets. The robust methodology and analytical procedure employed those not only allow for reproducibility of our study but also provides reliable estimates for our findings. Conversely, a notable weakness is that the cross-sectional design makes it impossible to draw causal inferences between the socio-demographic characteristics of adolescents and motherhood. Also, considering the sensitive nature of the questions posed to adolescents to ascertain their motherhood status, some of the responses might have been affected by social desirability bias, whereby some adolescents would respond to conform to social expectations as opposed to the reality. Finally, since the study was based on data from NDHS, only adolescent females aged 15-19 years were included. As a result, the estimation of adolescent pregnancy in this study might have been under-or overestimated.

Conclusion
Having investigated patterns and associated factors of teen motherhood, our study revealed a surge in teenage motherhood in Nigeria between 2008 and 2018, from 50.9 to 55.2%. Poverty, low or no education, marital union, early sexual debut, and being a resident in the South-South region contributed positively to teen motherhood in Nigeria.
The findings highlight the need for Government at all levels to strengthen efforts toward a favorable policy framework and system for free and compulsory education that will propel education to higher or tertiary level especially for adolescent girls, for Nigeria to derive the full benefit of the role of education in mitigating adolescent pregnancy (Elina & Pradhan, 2015). This can help mitigate the chances of early marriage and associated economic hardships, which hitherto truncates female's negotiation power and thereby plunging them into diverse conditions leading to unplanned and premature motherhood.
Furthermore, sexual and reproductive health services including sex education programs like comprehensive sexuality education should be realigned to take care of the vulnerable poor, while access to universal health care coverage and SRHR information should be prioritized using affordable healthcare financing mechanisms, adolescent/youth-centered responsive policies and adolescent/youth-led innovative and digital methods to mitigate the existing inequality in sexual and reproductive health and right information and services.
In the light of the regional variations in teen motherhood, it is expedient for the health sector to review the distribution and allocation of adolescent-friendly reproductive health services within the country to make it easily accessible irrespective of location. We advocate for further studies to investigate the impact of regional level health systems, as well as social and cultural norms of adolescent sexual and reproductive health concerns that expose them to teen motherhood. We also recommend the extensive promotion of contraception (e.g. IUD) among teenagers as this can help salvage the situation.
Knowledge of modern contraception was aligned with higher prospects of teen motherhood, and this suggests that knowledge does not directly translate to effective utilization. Consequently, government agencies and nongovernmental agencies that focus on adolescent reproductive health and contraception education, would have to examine whether adolescents possess the right knowledge and sufficient factors required to translate contraception knowledge to effective contraception utilization. A nationwide study on this subject may be worthwhile to explore the content of the knowledge held by these adolescents and possible reasons accounting for the gap between contraception knowledge and usage. With these measures, Nigeria's prospects of leaving no one behind and achieving the Sustainable Development Goal 3 may be enhanced.

Implications and contribution
This study highlights the increasing risk of teen motherhood in Nigeria over a decade, particularly among sexually active adolescents who are at higher risk of getting pregnant. Increasing efforts toward teen contraceptive knowledge and use, early comprehensive sexuality education, and female education up to the tertiary level as well as avoiding early sexual initiation could help mitigate against teen motherhood.