Table 6.

Comparison of Self-reported Cycle Length With Actual Cycle Length, of Actual Cycle Length in Cycles 1 and 2, and of the Timing of the Monitor Peak in Cycle 1 Versus Cycle 2 Among Participants in the BioCycle Study, Buffalo, New York, 2005–2007

No. of Days’ Difference	Self-reported Cycle Length vs. Actual Cycle Length				Actual Cycle Length (Cycle 1 vs. Cycle 2)		Day of Monitor Peak (Cycle 1 vs. Cycle 2)a		Days From End of Cycle of Monitor Peak (Cycle 1 vs. Cycle 2)a
	Cycle 1		Cycle 2
	No.	%	No.	%	No.	%	No.	%	No.	%
0	33	13.8	36	17.2	21	10.1	30	20.3	37	27.0
1	49	20.4	52	24.9	55	26.3	43	29.1	45	32.9
2	54	22.5	38	18.2	32	15.3	21	14.2	20	14.6
≥3	104	43.3	83	39.7	101	48.3	54	36.5	35	25.6
Unknownb	9		23		23				11

^aAmong 148 women who reached peak fertility in cycles 1 and 2.

^bAmong women with any monitor data, the actual cycle length was unknown for 9 women for cycle 1 and 23 women for cycle 2; 11 women who peaked in both cycles were missing cycle length data.