Table 3.

Prenatal/Perinatal factors and risk of MS in the nurses’ mothers’ subcohort

Variable	# Participants^a	# Cases^a (incident and prevalent^b)	Multivariate-adjusted^c : Rate Incident cases and prevalent cases Ratio (95% CI)	Multivariate-adjusted^c: Incident cases only Rate Ratio (95% CI)
Parental factors
Maternal pre-pregnancy BMI (kg/m²)
<18.5	3568	7	0.39 (0.18–0.83)	0.43 (0.19–0.98)
18.5–24.9	27317	149	1.0	1.0
25+	2404	20	1.67 (1.04–2.69)	1.56 (0.89–2.74)
P fortrend			0.001	0.003
Maternal education at birth
<4 yrs high school	4802	24	0.70 (0.22–2.25)	1.08 (0.66–1.76)
High school graduate^d	16518	95	1.0	1.0
College	13037	63	1.00 (0.42–2.38)	0.66 (0.44–1.00)
Father born in the US
Yes^d	33813	173	1.0	1.0
No	1763	10	1.40 (0.29–6.75)	0.62 (0.22–1.69)
Parents living together at birth
Yes^d	34483	179	1.0	1.0
No	422	5	3.95 (1.01–15.37)	3.95 (1.01–15.37)

Maternal medical conditions and healthcare utilization during pregnancy
Diabetes during pregnancy
Yes	158	2	10.19 (2.47–42.07)	Not estimable (no cases)
No^d	33839	173	1.0
Preeclampsia/toxemia
Yes	1212	9	1.46 (0.73–2.92)	1.65 (0.79–3.44)
No^d	33319	167	1.0	1.0 (ref)
Proteinuria
Yes	580	4	1.99 (0.73–5.43)	1.98 (0.73–5.43)
No^d	33701	172	1.0	1.0
Infection during pregnancy
Yes	886	6	1.48 (0.65–3.36)	1.66 (0.67–4.10)
No^d	33494	171	1.0	1.0
Immune-related factors^e
0^d	32719	162	1.0	1.0
1+	2003	16	1.49 (0.69–3.20)	1.86 (1.05–3.28)
Weight gain during pregnancy (lbs)
<15	4833	37	1.67 (1.04–2.68)	1.40 (0.88–2.22)
15–29	20650	95	1.0	1.0
30+	7455	42	1.21 (0.84–1.74)	1.16 (0.76–1.77)
P for trend			0.53	0.74
Sleep medication use
Yes	198	4	3.99 (0.42–37.48)	1.09 (0.15–7.95)
No^d	34139	175	1.0	1.0
Prenatal care
None or after 1^st trimester	3699	27	1.55 (1.02–2.35)	1.63 (1.00–2.85)
1^st trimester^d	30895	149	1.0	1.0

Maternal activity during pregnancy
Manual labor at home or work during pregnancy
Yes	1685	6	0.69 (0.30–1.56)	0.62 (0.22–1.69)
No^d	33349	170	1.0	1.0

Perinatal factors
Birth length (inches)
<18	688	5	1.62 (0.66–3.99)	1.77 (0.65–4.88)
19–22 ^d	24943	123	1.0	1.0
23+	296	1	0.91 (0.13–6.59)	0.91 (0.13–6.59)
P for trend			0.55	0.57

Composite Score
Obstetric suboptimality score
0–1^d	16112	81	1.0	1.0
2	9385	46	0.92 (0.64–1.32)	0.97 (0.63–1.49)
3+	10367	57	1.06 (0.75–1.50)	1.14 (0.76–1.71)
P for trend			0.44	0.49

For each factor, the number of cases and participants may not add up to the total number in the study due to missing exposure values.

Incident cases are those diagnosed after cohort recruitment (1989–2003), prevalent cases are the cases diagnosed after age 19 and before cohort recruitment in 1989

Controlling for age in months, calendar year, latitude at birth, SES (paternal occupation), sibship size, pack-years of smoking in adulthood, quintile of vitamin D intake.

Reference category.

Includes infections, preeclasmpsia/eclampsia, and proteinuria.