Table 2.

Sexual Activity During Study Follow-up Among 2751 African Heterosexual HIV-Serodiscordant Couples With an Initially HIV-Uninfected Female Partner, by Reproductive Stage

Variable	Nonpregnant/Nonpostpartum Periodsa	Early Pregnancy		Late Pregnancy		Postpartum Period
		Value	P	Value	P	Value	P
Total sex acts reported with study partner, no.	256462	7548		7205		3573
Total condomless sex acts reported with study partner, no.	25946	1530		947		327
Total person-months during follow-up, no.	55504	1602		2224		1541
Sex acts with study partner
No./person-month (95% CI)	4.62 (4.60–4.64)	4.71 (4.61–4.82)		3.24 (3.17–3.32)		2.32 (2.24–2.40)
RR for the mean frequency
Crude (95% CI)	1.00	1.11 (1.01–1.21)	.02	0.70 (0.63–0.78)	<.0001	0.48 (0.42–0.55)	<.0001
Adjustedb (95% CI)	1.00	1.04 (0.95–1.14)	.40	0.66 (0.59–0.73)	<.0001	0.45 (0.39–0.51)	<.0001
Condomless sex acts with study partner
No./person-month (95% CI)	0.47 (0.46–0.47)	0.96 (0.91–1.00)		0.43 (0.40–0.45)		0.21 (0.19–0.24)
RR for the mean frequency
Crude (95% CI)	1.00	2.64 (2.10–3.31)	<.0001	0.97 (0.70–1.32)	.83	0.55 (0.29–1.04)	.07
Adjustedb (95% CI)	1.00	2.43 (1.91–3.10)	<.0001	0.91 (0.66–1.25)	.55	0.51 (0.27–0.97)	.04

Early pregnancy was defined as the interval from the start of pregnancy (typically the time of the last menstrual period) to gestation week 13. Late pregnancy was defined as the interval from gestation week 14 to the end of pregnancy. The postpartum period was defined as the interval from the end of pregnancy to month 6 after delivery (for women with live births), week 6 after pregnancy loss (for women with pregnancy loss at gestation week ≥20 or newborn death), or week 4 after pregnancy loss (for women with pregnancy loss during gestation weeks 6–19).

Abbreviations: CI, confidence interval; RR, relative risk.

^aReference group for comparisons is time spent during the nonpregnant and nonpostpartum periods.

^bAdjusted for female age and duration of relationship with HIV-infected study partner.