Where Does the Sahelian Fertility Transition Stall? Higher-Order Parity Progression in Burkina Faso, Mali, and Niger

In the vast, sun-baked expanse of the Sahel, a region stretching across the southern edge of the Sahara Desert, families are having more children than almost anywhere else on Earth. For decades, demographers have watched this region with a mix of concern and curiosity, trying to understand why the number of children per woman remains stubbornly high while other parts of Africa have seen those numbers drop. The standard way to measure this is the total fertility rate, a single number that tells us the average number of children a woman will have in her lifetime. But this number acts like a blurry photograph; it tells us the final count, but it hides the story of how that count was reached. It cannot tell us if a woman stopped having children early because she chose to, or if she simply started later and stopped later. To understand the true shape of family life, researchers must look at the sequence of births, one by one, asking a different question: at which specific child does the decision to stop making families begin to take hold?

A team of researchers set out to answer this question by examining the lives of nearly 45,000 women across three neighboring countries: Burkina Faso, Mali, and Niger. These nations share a similar landscape, a predominantly Muslim and rural population, and a history of colonial administration, yet they sit at different stages of a demographic shift. While the average woman in Burkina Faso has about 4.4 children, her counterpart in Niger has over 6. The researchers wanted to know where the difference actually lies. Is it in the decision to have a first child, or does it happen much later, after a family has already grown? By piecing together detailed birth histories from national surveys conducted between 2021 and 2024, they mapped the journey of motherhood in these countries, tracking the probability that a woman with one child would go on to have a second, a third, and so on, all the way to her eighth or ninth child.

The story that emerged from the data was strikingly clear. In all three countries, the path to motherhood begins almost identically. Whether a woman lives in Burkina Faso, Mali, or Niger, the likelihood of having a first, second, or third child is nearly the same. Almost every woman who has a first child goes on to have a second, and almost every woman with two children goes on to have a third. The divergence does not start at the beginning of the family; it starts after the third child. This is the point where the paths of these three nations begin to separate. In Burkina Faso, the country furthest along in this transition, the likelihood of a woman with three children having a fourth begins to drop noticeably. In Mali, this drop is smaller, and in Niger, it is barely there at all. As the family grows larger, the gap widens. By the time a woman has six children, the difference in behavior is stark. In Burkina Faso, fewer than seven out of ten women with six children go on to have a seventh. In Mali, that number rises to eight out of ten, and in Niger, nearly nine out of ten women continue to the next birth.

The researchers found that this pattern explains almost the entire difference in family size between these nations. The gap in the average number of children is not caused by women in one country starting later or having fewer children in their early twenties. Instead, the difference is generated almost entirely by the decisions made by women who already have three or more children. In fact, the choices made after the third birth account for more than 90 percent of the difference between Burkina Faso and Niger. This finding challenges the idea that fertility transitions are driven primarily by delaying the first birth or by family planning programs targeting teenagers. The data suggests that the real turning point for these families happens much later, when the family is already substantial.

Furthermore, the study revealed that these three countries are not just at different points on the same road; they are traveling on different types of roads. In Niger, the pace of family growth has barely changed over the last two decades. Women there continue to have children at a steady, rapid pace, with very little variation based on how many children they already have. This represents a pre-transitional state where the decision to stop having children has not yet taken hold. In Mali, the situation is different. Women there are waiting longer between each child, but they are doing so uniformly. Whether they have two children or six, the time they wait before having the next one has increased by roughly the same amount. This suggests a pattern of postponement, where families are stretching out their reproductive years without necessarily deciding to stop at a specific number.

Burkina Faso tells a third story. Here, the delay between children gets longer as the family grows, but the likelihood of having another child also drops sharply as the number of children increases. A woman with six children in Burkina Faso is not just waiting longer than a woman with two; she is significantly less likely to have a seventh child at all. This indicates a shift toward a specific limit on family size, a decision to stop that becomes stronger with each additional child. This is a more advanced stage of transition, where the desire to limit family size is superimposed on the general trend of waiting longer between births. The researchers observed that this shift toward limiting family size is most pronounced among women who have already had three or more children, a group that is often older, more rural, and less likely to be reached by standard health programs focused on adolescents or first-time mothers.

The study also looked at how these patterns have changed over time. In Burkina Faso, the decline in the likelihood of having another child has become steeper with each passing decade, particularly for women with higher numbers of children. In Mali, the change has been more uniform, and in Niger, there has been very little change at all. This suggests that the transition is not a single event that happens to a whole population at once, but a gradual process that moves through different stages. The first stage involves simply waiting longer between births, as seen in Mali. The second stage involves making a conscious decision to stop having children after a certain number, as seen in Burkina Faso. Niger appears to be in the earliest phase, where neither of these shifts has fully taken hold.

These findings have important implications for how we understand and support families in the Sahel. For years, public health efforts have focused heavily on adolescents and young mothers, aiming to delay the first birth or ensure spacing for the first few children. While these efforts are vital, the data suggests they are missing the segment of the population where the real change is happening. The women who are deciding to stop having children are often those who already have three or more kids. They are older, often living in remote rural areas, and may have less contact with health services than younger women. If the goal is to support families in achieving their desired family size, the focus may need to shift to include these older mothers, offering them a wider range of family planning options and ensuring they have access to the care they need to make informed choices.

The researchers also noted that the death of a child plays a significant role in these decisions. In all three countries, if a child dies, the mother is much more likely to have another child to replace them. This "replacement" effect is particularly strong at the higher parities, where the decision to stop might otherwise be taking hold. This links the health of children directly to the size of families, suggesting that improving child survival rates could be a powerful, indirect way to help families achieve smaller sizes if that is their wish.

Ultimately, this study provides a clearer picture of the complex landscape of family life in the Sahel. It shows that the difference between a family of five and a family of seven is not found in the first few years of motherhood, but in the later years, when the family is already large. It reveals that the transition to smaller families is not a single, uniform process, but one that unfolds in distinct stages, with different countries moving at different speeds and through different mechanisms. By looking beyond the average number of children and examining the specific choices women make at each step of their reproductive journey, we can better understand the forces shaping the future of these communities. The story of fertility in the Sahel is not just about how many children are born, but about when and why the decision to stop is made, and for many women, that decision is being made long after the first child has grown up.