Table 3.

Adjusted RRs (95% CI) for incidence of GDM according to changes in menstrual cycle characteristics among 10,906 premenopausal women who contributed 14,418 pregnancies from the NHS II (1993–2009)

Changes in menstrual cycle characteristics	GDM/pregnancies		RRs (95% CI)
			Multivariable modelsa		Final models adjusted for lifestyle factorsb
Change in regularity from age 14–17 to 29–46 years
Maintaining regular	234/6493		1.00 (reference)		1.00 (reference)
Regular to irregular	18/268		1.70 (1.07, 2.72)		1.43 (0.89, 2.29)
Irregular to regular	83/2287		1.02 (0.79, 1.30)		1.02 (0.80, 1.31)
Irregular maintained	38/787		1.36 (0.98, 1.89)		1.21 (0.87, 1.67)
OC user	205/4583		1.24 (1.03, 1.49)		1.21 (1.01, 1.46)
Change in regularity from age 18–22 to 29–46 years
Maintaining regular	142/3912		1.00 (reference)		1.00 (reference)
Regular to irregular	12/145		1.96 (1.10, 3.49)		1.68 (0.93, 3.01)
Irregular to regular	37/1104		0.92 (0.64, 1.31)		0.94 (0.66, 1.35)
Irregular maintained	22/445		1.33 (0.86, 2.04)		1.20 (0.78, 1.83)
OC user	365/8812		1.18 (0.98, 1.43)		1.17 (0.96, 1.42)
Change in length from age 18–22 to 29–46 years
Maintaining <32 days	123/3558		1.00 (reference)		1.00 (reference)
<32 to ≥32 days	28/408		2.13 (1.44, 3.16)		1.98 (1.34, 2.92)
≥32 to <32 days	29/774		1.08 (0.73, 1.61)		1.10 (0.73, 1.63)
≥32 days maintained	33/866		1.11 (0.77, 1.62)		1.04 (0.71, 1.50)
OC user	365/8812		1.26 (1.03, 1.54)		1.24 (1.01, 1.52)

^aMultivariable model was adjusted for age (continuous), age at menarche (continuous), BMI at age 18 years (continuous), ethnicity (white or others), family history of diabetes (yes or no) and parity (1, 2, 3 or ≥4)

^bBased on multivariable model with additional adjustment for time-varying alcohol consumption (0, 0.1–5.0 or ≥5.1 g/day), BMI (<23, 23–24.9, 25–29.9, 30–34.9 or ≥35 kg/m²), physical activity (<150 or ≥150 min/week), smoking status (never, past or current) and AHEI 2010 score (below or above median) during follow-up