Table 1.

Baseline Characteristics of 2,653 Women According to Usual Menstrual Cycle Length, Denmark, 2007–2009

Characteristica	Menstrual Cycle Length, days
	<25			25–26			27–29			30–31			32–33			≥34
	No.	%	Mean	No.	%	Mean	No.	%	Mean	No.	%	Mean	No.	%	Mean	No.	%	Mean
No. of women	116			229			1,482			589			121			116
Age, years			28.5			29.4			28.8			28.4			27.5			27.8
Partner’s age, years			31.2			31.8			30.9			30.9			30.6			30.5
Age at menarche, years			12.9			13.0			12.9			13.0			12.8			12.9
Body mass index, kg/m2			24.6			24.1			24.0			24.2			23.7			25.0
Physical activity, MET-hours/week			27.9			26.2			24.3			25.4			24.4			23.7
No vocational training		12.3			9.7			11.3			12.6			10.9			13.2
Parous		32.4			30.8			35.8			36.1			41.0			27.7
Current regular smoker, yes		18.1			16.2			13.2			11.5			11.4			9.4
Pack-years of ever smoking			2.9			2.8			2.2			2.0			2.1			2.3
Mother smoked during pregnancy, yes		39.8			37.1			32.8			36.8			30.3			29.7
Alcohol intake (current), drinks/week			3.2			2.5			2.9			3.0			2.4			2.6
Caffeine intake (current), mg/day			109.0			110.3			109.1			101.6			105.1			108.8
Frequency of intercourse, ≥4 times/week		21.1			25.5			18.6			20.4			15.3			17.8
Last method of contraception
Barrier methods		27.3			28.7			28.8			29.4			43.9			31.1
Hormonal contraceptives		66.0			60.7			61.2			58.9			46.3			60.6
Withdrawal, charting, or other		6.7			10.6			10.0			11.7			9.8			8.3
Time to cycle regularity, years			2.2			2.2			2.2			2.6			3.1			3.9
Duration of flow ≥7 days		4.5			3.5			2.9			4.1			5.1			4.2
Amount of flow heavy or very heavy		17.3			15.9			17.9			19.7			16.4			17.3

Abbreviation: MET, metabolic equivalent.

^aAll characteristics, with the exception of age, are age standardized to the cohort at baseline.