Table 3.

Comparison of intercourse averaging weekly, every other day, and daily on simulated time to pregnancy and fecundability odds ratios^a over 12 cycles of follow-up in a cohort of 100,000 women^b (using Scenario 1^c relationship between sex and implantation)

	Weekly			Every other day				Daily
Cycle	Population at risk	% becoming pregnant	Cumulative pregnancy rate (%)	Population at risk	% becoming pregnant	Cumulative pregnancy rate (%)	FORd	Population at risk	% becoming pregnant	Cumulative pregnancy rate (%)	FORd
1	100,000	15.1	15.1	100,000	33.5	33.5	2.83	100,000	37.1	37.1	3.32
2	84,900	12.7	25.9	66,544	28.6	52.5	3.16	62,873	31.8	57.1	3.80
3	74,083	10.9	34.0	47,526	23.9	63.8	3.42	42,900	26.6	68.5	4.22
4	66,000	9.3	40.1	36,190	20.7	71.3	3.71	31,499	23.1	75.8	4.67
5	59,868	7.9	44.9	28,699	17.9	76.4	3.98	24,222	20.1	80.6	5.12
6	55,132	6.9	48.7	23,572	15.2	80.0	4.22	19,364	17.0	83.9	5.51
7	51,335	5.8	51.7	19,982	13.2	82.7	4.46	16,070	14.7	86.3	5.89
8	48,352	4.9	54.0	17,343	10.9	84.6	4.66	13,713	12.2	88.0	6.22
9	45,974	4.3	56.0	15,455	9.7	86.0	4.84	12,035	10.7	89.3	6.52
10	44,004	3.6	57.6	13,963	8.0	87.2	5.00	10,749	8.8	90.2	6.78
11	42,401	3.0	58.9	12,842	6.7	88.0	5.14	9,799	7.4	90.9	7.01
12	41,141	2.6	59.9	11,977	6.3	88.8	5.28	9,069	7.2	91.6	7.28

^aFecundability odds ratios for every other day and daily calculated relative to weekly intercourse

^bAnovulation set equal to 8% for each cycle of observation; probability of implantation|fertilization = 70% and probability of fertilization|sex & ovulation = 59% for the first cycle of observation, followed by a 7.5% reduction per cycle for implantation|fertilization and fertilization|sex & ovulation; probability of implantation calculated using Equation 1.

^cScenario 1: among fecund couples attempting conception, the maximum probability of attaining pregnancy is ~38% when sexual intercourse always occurs in the fertile window (sex = 1.0)¹⁵.

^dFecundability Odds Ratio