Background: The fertility transition started later in sub-Saharan Africa than in other regions of the world. Moreover, the average number of children per woman declined more slowly there, owing to a distinct mechanism of fertility reduction. It has been argued that the fertility decline in sub-Saharan Africa proceeded through an increase in birth intervals rather than by a limitation of the number of births.

Objective: We analyze the fertility transitions in 29 countries to determine which mechanism women resort to in order to reduce their number of children.

Methods: Using multiple sample surveys, we estimate and cross-validate trends in parity progression ratios and birth intervals. We identify sub-regional regularities and vanguard trends in the interplay between the dynamics of the lengthening of birth intervals and birth limitation over the period 1962‒2012.

Results: While initial fertility declines were driven by a lengthening of birth intervals at all parities, we observe a recent onset of birth limitation in regions and countries that are most advanced in the fertility transition.

Conclusions: The experience of sub-Saharan Africa shows that if all parities contribute to the fertility transition from the outset, the main drivers of the fertility decline switch from a lengthening of birth intervals to a limitation of family size when the average fertility reaches about five children per woman.

Contribution: Our findings point to the emergence of birth limitation as a new stage in the fertility transition in sub-Saharan Africa. These results have implications for future fertility declines in sub-Saharan Africa.