Table 5.

ORs and 95% CIs of change in menstrual cycle characteristics concerning SARS-CoV-2 infection and COVID-19 vaccination status, stratified by menstrual cycle characteristics at baseline (participants who had regular [within 7 days] and normal [26–31 days] cycle length [n=1976] vs participants who had irregular [>7 days] or short or long [<26 or ≥32 days] [n=1140] cycle length), the Nurses’ Health Study 3

Change in usual menstrual characteristics	SARS-CoV-2 infectiona		COVID-19 vaccinationb
	Baseline menstrual cycle characteristics		Baseline menstrual cycle characteristics
	Regular and normal length OR (95% CI)	Irregular or short or long cycle OR (95% CI)	Regular and normal length OR (95% CI)	Irregular or short or long cycle OR (95% CI)
Change in cycle length or regularity
Any change	0.82 (0.61–1.11)	0.90 (0.56–1.46)	0.94 (0.66–1.32)	1.83 (1.12–3.00)
Change in cycle length
Any change	0.80 (0.58–1.10)	1.02 (0.70–1.50)	1.19 (0.83–1.71)	1.69 (1.12–2.54)
Change in cycle lengthc
Shorter	0.85 (0.58–1.22)	0.97 (0.62–1.50)	1.33 (0.87–2.05)	1.32 (0.85–2.06)
Longer	0.68 (0.42–1.11)	1.10 (0.68–1.77)	0.95 (0.56–1.60)	2.82 (1.51–5.27)
Change in cycle regularity
Any change	0.89 (0.66–1.20)	0.97 (0.66–1.42)	0.77 (0.55–1.08)	1.05 (0.69–1.59)
Change in cycle regularityc
More regular	0.82 (0.52–1.30)	0.83 (0.54–1.29)	0.82 (0.51–1.34)	1.05 (0.66–1.66)
Less regular	0.90 (0.64–1.25)	1.22 (0.76–1.97)	0.74 (0.51–1.08)	1.01 (0.59–1.74)

Change in cycle characteristics was defined by change in 3 categories: cycle regularity ([1] very regular [±3 days], [2] regular [within 5–7 days], [3] usually irregular or always irregular or no period) or cycle length ([1] <26 days, [2] 26–31 days, or [3] ≥32 days). Multivariable models were adjusted for age at baseline, follow-up time, body mass index at end of follow-up, weight change, race and ethnicity, educational attainment, and region and mutually adjusted for SARS-CoV-2 infection and COVID-19 vaccination with each other. Of note, 742 hormonal contraception users at MOD2 were excluded from analysis.

CI, confidence interval; OR, odds ratio.

Wang. COVID-19 infection and vaccination and menstrual cycle changes. Am J Obstet Gynecol 2022.

^aReference: uninfected

^bReference: unvaccinated

^cMultinomial logistic model.