Risk of Human Papillomavirus (HPV) Infection and Cervical Neoplasia after Pregnancy

Table 2 Crude and adjusted odds ratios (ORs) for the association between HPV detection or squamous intraepithelial lesion (SIL) and pregnancy

Outcome	Post pregnancies observation visits (n)		Crude OR	95 % CI	Adjusted OR^c	95 % CI
	No pregnancy	Pregnancy	Crude OR	95 % CI	Adjusted OR^c	95 % CI
HPV^b	^aHPV (−/+)	^aHPV (−/+)
Any HPV	19948/3787	23/6	0.85	(0.33–2.14)	0.80	(0.31–2.07)
Any HR-HPV	19948/2281	23/3	0.80	(0.24–2.65)	0.80	(0.24–2.71)
LR-HPV only	19948/1506	23/3	1.15	(0.31–4.23)	1.18	(0.34–4.15)
Species^b
3	19948/638	23/1	1.49	(0.26–8.50)	1.32	(0.22–7.97)
5	19948/343	23/1	2.32	(0.35–15.23)	1.86	(0.28–12.15)
6	19948/505	23/1	1.06	(0.11–9.83)	0.91	(0.10–8.12)
7	19948/645	23/1	1.23	(0.20–7.60)	0.98	(0.15–6.24)
9	19948/1407	23/1	0.48	(0.07–3.21)	0.43	(0.07–2.59)
10	19948/303	23/1	1.26	(0.09–17.40)	1.29	(0.13–12.93)
Group
1 (species-1/8/10/13)	19948/399	23/1	0.93	(0.64–13.53)	1.05	(0.10–10.53)
2 (species-5/6/7/9/11)	19948/2566	23/4	0.87	(0.29–2.56)	0.77	(0.27–2.21)
3 (species-2/3/4/15)	19948/716	23/1	1.41	(0.26–7.64)	1.25	(0.21–7.29)
Squamous intraepithelial lesions (SILs)	SIL (−/+)	SIL (−/+)
Low-grade SILs	23845/258	28/0	--	--	--	--
High-grade SILs	23845/76	28/1	7.77	(0.93–65.08)	8.75	(1.00–77.03)
Any-grade SILs	23845/334	28/1	0.91	(0.05–18.27)	0.84	(0.46–15.33)

^aExcludes women-visits for which HPV testing was invalid or missing
^bSee text for definition of grouped HPV genotypes
^cAdjustment for empirical confounders was done using a 5 % Change-in-Estimate Method (variables that changed the estimates by +/− 5 % were included in the model) considering the following variables as a potential confounder: age at enrolment (linear), race (white, non-White), marital status (single, married, widowed, separated, unmarried but living with partner), income (quartiles of income), smoking (never, current, former), age at first sexual intercourse (≤15, 16–17, 18–19, 20+), number of previous pregnancies (0–1, 2–3, 4–6, 7+), Pap testing before enrollment in the cohort (yes, no), and lifetime number of sexual partners (0–1, 2–3, 4+). Adjustment for HPV status (negative, LR-HPV only, any HR-HPV) was considered for the analysis of SILs. Confounding variables added to the multivariate models for HPVs (variables that changed the OR for the relation between pregnancy and HPV status by +/− 5 %) were: number of previous pregnancies, age at first sexual intercourse, age, race and smoking status. For SILs, confounding variables added to the multivariate models were: HPV status, age, smoking, race, age at first sexual intercourse, number of previous pregnancies and Pap testing before entering the cohort

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