Gestational age-related changes in the cellular composition of peripheral blood have not been described in sub-Saharan African settings. We conducted longitudinal cohort studies in Beninese and Tanzanian mothers with quantification of peripheral blood mononuclear cell-types ex vivo using flow cytometry. Between the second trimester and delivery the frequency of CD4(+) T cells declined significantly, contrasting with a non-significant increase in CD8(+) T cells, but no changes in T-regulatory, NK or NKT cell frequencies. Antigen-presenting cell profiles were also unaltered, although non-significant trends were evident. These changes resemble in some respects those reported during pregnancies in developed countries, but differ in others.