Introduction

Fertility is a key factor in population dynamics that affects the size and growth of populations [1]. Globally, fertility rates have been declining, with the current rate standing at 2.25 live births per woman, which is one child less than in 1990. However, women in sub-Saharan Africa (SSA) countries have an average of four or more births, and the region’s population growth remains high. The population of SSA is projected to rise from 1.1 billion in 2022 to over 2 billion by 2050 and 3.44 billion by 2100. Although the average number of births per woman in SSA is expected to decline from 4.6 in 2021 to 3.0 in 2050 [2,3], fertility remains above replacement levels. Additionally, women in SSA experience higher levels of unrealized fertility and fertility desires [4–6]. These SSA women have more difficulty translating their fertility preferences into birth outcomes compared to women in other low- and middle-income countries (LMICs) [7].

Fertility desires and intentions impact a woman’s fertility decisions, choices, behavior, and achievements at different stages of her life [8]. Fertility is considered achieved when the number of children a woman desires matches the number she have. Conversely, unrealized fertility occurs when a woman has fewer children than she desires. In essence, unrealized fertility refers to the situation in which women in the later stages of their reproductive years are unable to meet their ideal fertility goals [4,5].

Unrealized fertility is more prevalent in LMICs, such as SSA, North Africa, Latin America, and South and Southeast Asia [4]. Within these, SSA experiences notably higher rates, with 40% of women facing unrealized fertility compared to 26% in non-SSA countries. Furthermore, unrealized fertility varies across African regions, with western and central Africa exhibiting the highest rates, followed by eastern and southern Africa [6,9–11].

Achieving the desired level of fertility requires individuals to have control over their reproductive decisions. That is, people have the right to make their own decisions about their fertility preferences without interference. However, not all women are equally vulnerable to failure to reach fertility goals, suggesting that certain factors contribute to unrealized fertility. A handful of studies have assessed these factors that potentially contribute to the occurrence of unrealized fertility in LMICs, including SSA [4,11]. These studies indicated that higher levels of education, higher wealth quintiles, and contraceptive use as are associated with unrealized fertility. In contrast, the impact of factors such as experiencing child death and the working status of women on unrealized fertility remains under explored.

While most research in SSA has focused on high fertility rates and the unmet need for contraception, it is important to examine women who wish to have more children but are unable to reach their desired family size. Exploring the factors that contribute to unrealized fertility can help understand reproductive behaviors and family planning needs. This leads to the development of effective family planning initiatives that support women in achieving their desired family size, while also respecting individual reproductive rights and enhancing overall societal well-being. We investigated unrealized fertility among women aged 40–49 in SSA, who are approaching the end of their reproductive years, making them an appropriate group for comparing the number of their living children and fertility preferences [10]. This study assessed the factors influencing unrealized fertility in 19 SSA countries, aiming to provide new insights into why intentions do not always translate into reality.

Methods

Data source and sampling procedure

This study is based primarily on 19 SSA countries that have conducted their most recent demographic and health surveys (DHS), not including the mini-DHS, in phase 8 (2018–2023) to have the same available variables and up-to-date data. Within each country, the cross-sectional survey used a two-stage cluster sampling technique. The first step involved the random selection of enumeration areas (EAs), whereas the second stage involved the selection of households. The Individual Women’s Record dataset (IR file) was used. The DHS survey data from the 19 SSA nations were combined, and a weighted sample of 46,408 women between the ages of 40 and 49 was included [12]. The flow chart illustrating how the study samples were selected is depicted in Fig 1.

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Fig 1. Flowchart of the study.

https://doi.org/10.1371/journal.pone.0331265.g001

Results

Background characteristics of the participants

Among the total respondents, 36,410 (78.5%) were currently married and 20,079 (43.3%) had never attended formal education. Furthermore, approximately half of the participants (n = 22584, 48.7%) had exposure to family planning messages, and the majority (n = 26,883, 57.9%) were rural dwellers. Among the participants, (n = 21,103, 47%) gave birth for the first time before the age of 20, and three-quarters of the women were not using any form of contraceptive. With respect to family size, (n = 22,704, 48.9%) of the respondents’ ideal number of children was 6 + , (n = 15,515, 33.4%) had 6 or more living children, (n = 16,294, 35.1%) experienced child death, (n = 8,250, 17.8%) had an equal number of sons and daughters, (n = 14,366, 31%) had more sons, and (n = 13,737, 29.6%) had more daughters (Table 1).

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Table 1. Background characteristics and distribution of unrealized fertility of women at the end of their reproductive period in sub-Saharan Africa.

https://doi.org/10.1371/journal.pone.0331265.t001

Family size and fertility preferences

The mean ideal number of children was 5.8, which ranges from 4.2 in Rwanda to 6.7 in Nigeria and Mali. The mean age at first birth was 20.8 years, which was highest in Rwanda (22.5 year) and lowest in Liberia and Zambia (19.5 year). The mean numbers of children ever born, living children, and dead children in SSA were 5.2 (ranging from 4.0 in Gabon to 6.5 in Mali), 4.5 (ranging from 3.8 in Gabon to 5.4 in Mali), and 0.65 (ranging from 0.25 in Gabon to 1.13 in Mali), respectively (Table 2).

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Table 2. Mean of fertility preference and family size of women at the end of their reproductive period in sub-Saharan Africa by country.

https://doi.org/10.1371/journal.pone.0331265.t002

Pooled prevalence of unrealized fertility

The pooled prevalence of unrealized fertility was 61.43% (95% CI: 57.63, 65.24), in which Rwanda (37.40; 95% CI: 27.92, 46.88) and Sierra Leone (69.34; 95% CI: 60.30, 78.38) had the lowest and highest prevalence, respectively (Fig 2). The prevalence of unrealized fertility was higher among women whose ideal number of children was more than six (78.6%), whose age at first birth was 30 year or above (81.1%), whose all children were of the same sex (83.5% for all sons and 82.5% for all daughters), and those who had experienced child death (67.7%) than their counterparts (Table 1).

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Fig 2. Forest plot of the pooled prevalence of unrealized fertility among women at the end of their reproductive period in sub-Saharan Africa.

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Factors associated with unrealized fertility

The ICC value in the null model was 13.26% (95% CI; 12.15%, 14.47%), indicating that 13.26% of the overall variability in unrealized fertility resulted from between-cluster variability, whereas the remaining 86.74% of the overall variability was attributable to individual variation. Therefore, to obtain robust estimates in the presence of this clustering effect, a multilevel model was considered. In the bi-variable analysis, the sex of the household head, education level, wealth index, age at first birth, marital status, contraceptive utilization, exposure to family planning messages, working status, sex composition, experienced child death, and residence status were selected with p values <0.2. In the multivariable multilevel robust Poisson regression analysis, educational status, age at first birth, contraceptive utilization, working status, sex composition, experiencing child death, and residence were significantly associated with unrealized fertility.

The prevalence of experiencing unrealized fertility among women who reached primary, secondary, and higher education decreased by 15% [aPR = 0.85, 95% CI: 0.83, 0.87], 11% [aPR = 0.89, 95% CI: 0.87, 0.91], and 11% [aPR = 0.89, 95% CI: 0.85, 0.92], respectively, compared with women who had no formal education. Women aged 20–24 years, 25–29 years, and 30 years and above at their first birth had 1.05 times [aPR = 1.05, 95% CI: 1.04, 1.08], 1.20 times [aPR = 1.20, 95% CI: 1.17, 1.22], and 1.31 times [aPR = 1.31, 95% CI: 1.28, 1.34] higher prevalence of unrealized fertility, respectively, than women aged under 20 years. Women who were working were 1.03 times more likely [aPR = 1.03, 95% CI: 1.01, 1.05] to experience unrealized fertility compared to women who were not working. Compared with not utilizing any contraceptives, the use of traditional and modern contraceptives decreased the prevalence of experiencing unrealized fertility by 23% [aPR = 0.77, 95% CI: 0.73, 0.81] and 26% [aPR = 0.74, 95% CI: 0.72, 0.76], respectively. Compared with women who had an equal number of sons and daughters, women who had no child, women who had only sons, and women who had only daughters had a 1.31 [aPR = 1.31, 95% CI: 1.27, 1.35], 1.34 [aPR = 1.34, 95% CI: 1.30, 1.37], and 1.33 [aPR = 1.33, 95% CI: 1.30, 1.37] times higher prevalence of experiencing unrealized fertility, respectively. In contrast, women who have more sons than daughters and more daughters than sons had 10% [aPR = 0.90, 95% CI: 0.88, 0.92] and 11% [aPR = 0.89, 95% CI: 0.87, 0.91], respectively, decreased prevalence of unrealized fertility. The prevalence of having unrealized fertility among women who experienced child death increased by 25% [aPR = 1.25, 95% CI: 1.23, 1.27]. Compared with women from urban areas, the prevalence of unrealized fertility among women from rural areas decreased by 3% [aPR = 0.97, 95% CI: 0.95, 0.99] (Table 3).

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Table 3. Assessment of factors associated with unrealized fertility of women at the end of their reproductive period in sub-Saharan Africa (N = 46,408).

https://doi.org/10.1371/journal.pone.0331265.t003

Discussion

It has been agreed internationally that parents have the right to decide freely and responsibly on the number, timing, and spacing of their children [18,19]. In this context, our study explores the determinants of unrealized fertility in SSA. The pooled prevalence was high, and we found sociodemographic, reproductive, and contextual factors influencing unrealized fertility, including education level, age at first birth, contraceptive utilization, working status, sex composition of children, experiencing child death, and place of residence.

The pooled prevalence of unrealized fertility among women aged 40–49 years in SSA was 61.43 (95% CI: 57.63, 65.24). This was in line with a report from a previous study in LMICs [20], where unrealized fertility was 62% in western and central Africa. A related study conducted in Nigeria found that the prevalence of unrealized fertility was 13.5% when measured by the indicator “desire for another child.” However, when the indicator “ideal number of children” was used as the measurement, the prevalence rose significantly to 59.2%, which aligns with our findings [21]. A study revealed that 36% of women in Ghana experienced underachieved fertility [15], which is lower than our findings. This disparity arises from variations in how the outcome variable is measured. Our outcome variable was measured by the difference between the ideal number of children and the number of living children, as stated by Casterline and Han [13]. However, the Ghanaian study calculated the difference between the ideal number of children and the total number of children ever born to measure underachieved/unrealized fertility [4].

According to our results, women who reported having no children, only son/s, or only daughter/s were more likely to report a higher prevalence of experiencing unrealized fertility. In contrast, the possibility of having unrealized fertility was less prevalent among women who have both sons and daughters of unequal numbers than among those with equal numbers of sons and daughters. Parental preference for the sex composition of children is one of the factors that influences fertility [21–24], particularly in LMICs, where a strong preference for sons or daughters affects the likelihood of having more children. Gender preferences vary widely across different countries and regions, with balance preference being the most common type globally. However, the daughter preference was more prevalent in Latin America, the Caribbean, and some Southeast Asian countries, whereas the son preference was dominant in southern Asia, western Asia, and northern Africa [25]. In SSA, there is little evidence of sex preference, primarily a mix of son and daughter preferences, with son preference being more common in Western Africa and daughter preference in other regions [11,25]. A qualitative study from Brazil revealed that couples’ desire for children varies based on the number of children they have, where most desire more than what they have and having children of each sex [26]. Our finding shows that while women may prefer to have both sons and daughters rather than children of only one sex, the actual number of sons and daughters they have is not as influential as long as they have children of both sexes and achieve their desired total number of children.

As the age of a woman at her first birth is delayed to older ages, it is more likely to have a higher prevalence of unrealized fertility. This finding is in line with other previous studies [4,21]. Women are born with a finite number of eggs, which decrease in both quality and quantity as they age. Fertility declines in women in their early 30s, notably after age 35, with a 44% chance of conceiving within a year by age 40. Therefore, an older age at childbearing is characterized by decreased chances of conception, increased risks of miscarriage and pregnancy complications, and longer times to achieve pregnancy [27,28]. Consistent with studies performed in Nigeria [14] and Ghana [15], a high prevalence of unrealized fertility was more likely to be experienced among women who experienced child death. A possible explanation could be that in SSA, where there is high child mortality and a desire for larger family sizes (based on the results presented in Table 2), the discrepancy between desire and reality leads to underachieved fertility.

Women who used any method of contraceptive were less likely to attain unrealized fertility than their counterparts. This is supported by studies from LMICs [11,20]. Family planning helps achieve the desired family size because women use contraception to control their family size after they reach their ideal number of children [29]. In agreement with other studies [11,14,20], the more educated the mother is, the less likely she is to have unrealized fertility than mothers with no formal education. This is because educated women tend to have a more limited number of ideal family sizes and living children. In contrast, women with no formal education may have larger ideal family sizes, which leads to a greater likelihood of unrealized fertility if they cannot achieve those numbers. Additionally, those with lower levels of education are also more likely to experience unwanted fertility and pregnancies [30]. Women who are employed tend to have lower total fertility rates and a lower unmet need for family planning, and are more likely to use modern contraceptives compared to those who are not employed [31]. In support of this, our results revealed a statistically significant association between women’s working status and unrealized fertility. Women who reported that they were working or employed were more likely to have a higher prevalence of experiencing unrealized fertility.

Women residing in rural areas were found to have a lower prevalence of unrealized fertility than urban residents. This finding contradicts findings from other studies [11,14]. The difference may be due to variations in the age of study populations and the survey years. Those studies brought lack of resources in rural areas to support their findings. However, women in rural areas often have higher total fertility rates resulting from lower levels of education, economic conditions, and cultural norms that favor larger families compared to their urban counterparts. Additionally, lower employment status and poor knowledge of contraceptives contribute to higher fertility in rural areas [32–34]. Therefore, the lower likelihood of unrealized fertility among rural residents might be attributable to high fertility.

Conclusion

This study found that unrealized fertility is notably prevalent among women approaching the end of their reproductive period in sub-Saharan Africa. Older maternal age at first birth, being employed, having no children or only children of one sex, and experiencing child death contributed to higher prevalence of unrealized fertility . In contrast, higher maternal education, the use of contraceptives, having both male and female children, and residing in rural areas contributed to lower prevalence. Therefore, interventions targeting empowering women through education and finance contribute to deciding on the number of their children freely. Additionally, efforts to expand women’s access to education, family planning, and healthcare, alongside initiatives that challenge societal norms on sex preference and family size, are essential.

Acknowledgments

We acknowledge the MEASURE DHS program for consenting us to use the sub-Saharan Africa dataset.