Thymic output during and after pregnancy. The effect of pregnancy on CD4 counts (A), naive CD4 counts (B), and total CD4-TRECs (C) in 20 HIV-infected and 16 HIV-negative women. Measurements were performed at 3 time points during pregnancy (in the first, second, and third trimesters) and 2 to 6 months postpartum. (A) CD4 counts were at all time points significantly lower in HIV-infected women, and there was a significant effect of pregnancy (P < .0001) with increased CD4 counts postpartum. (B) Naive CD4 counts were significantly lower at all time points in HIV-infected women compared with controls (P = .0030), and there was a significant effect of pregnancy (P = .003). (C) Total CD4-TRECs tended to be lower in HIV-infected women (P = .057). No significant effect of pregnancy on total CD4-TRECs was demonstrated. Data are mean (± SEM). P values for time, group, and time × group effect in the mixed repeated models are shown. NS indicates not significant.