Table 6.

Measures of unprotected sex: time period (14 days, 60 days, or last sex), definition, and bivariate analysis between each unprotected sex measure and pregnancy at the subsequent wave

Measure with definition	Time period	Pregnant wave (%)			Pregnant wave 3 (%)
		No	Yes	p	No	Yes	p
Biomarker positive and no pregnancy prevention	14 days	4.5	14.2	****	7.0	12.8	*
No condom use, not currently taking oral contraception, or tested positive for Yc-PCR biomarker for unprotected sex
No condom or oral contraception use	14 days	7.6	12.7	*	7.9	12.9	+
No condom use and not taking oral contraception
Biomarker positive and no oral contraception	14 days	5.7	16.2	****	8.3	13.0
Positive Yc-PCR biomarker and not taking oral contraception
Biomarker unprotected sex	14 days	5.8	15.5	****	8.4	12.1
Positive Yc-PCR biomarker
No condom or oral contraception use	60 days	7.4	15.0	**	8.5	12.0
No condom use and not taking oral contraception
No condom use	60 days	7.5	14.2	*	8.5	11.6
Reported having used condoms in 0 episodes of vaginal sex
No pregnancy protection	Last sex	7.6	10.3		6.2	12.8	**
Reported using no method of pregnancy prevention at last sex and not taking oral contraception
No condom use	14 days	7.7	11.9		8.0	12.3	+
Reported having used condoms in 0 episodes of vaginal sex

Measures are sorted in decreasing order of significance for predicting pregnancy at both waves. The Y-chromosome PCR (Yc-PCR) biomarker for unprotected sex is sensitive to the presence of semen Y-chromosome for up to 14 days even during menses²⁹,³⁰,⁴⁴

+p ≤ 0.1; *p ≤ 0.05; **p ≤ 0.01; ***p ≤ 0.001; ****p ≤ 0.0001