Table 5.

Associations between number of preterm deliveries and subsequent risk of stroke among women with at least two singleton deliveries.

	Cases	Rate*	HR (95% CI)†	P
0-43 years after first delivery
0 preterm	16,627	56.2	Reference
1 preterm	2,265	77.5	1.32 (1.26, 1.38)	<0.001
≥2 preterm	659	104.7	1.80 (1.67, 1.95)	<0.001
Per additional preterm delivery			1.30 (1.27, 1.34)	<0.001
<10 years after first delivery
0 preterm	1,779	14.8	Reference
1 preterm	254	21.7	1.42 (1.25, 1.63)	<0.001
≥2 preterm	91	36.3	2.41 (1.95, 2.98)	<0.001
Per additional preterm delivery			1.46 (1.35, 1.58)	<0.001
10-19 years after first delivery
0 preterm	3,143	35.4	Reference
1 preterm	462	52.2	1.39 (1.26, 1.53)	<0.001
≥2 preterm	135	70.0	1.84 (1.55, 2.18)	<0.001
Per additional preterm delivery			1.33 (1.25, 1.41)	<0.001
20-29 years after first delivery
0 preterm	5,666	97.8	Reference
1 preterm	727	124.2	1.20 (1.11, 1.30)	<0.001
≥2 preterm	222	173.0	1.65 (1.44, 1.89)	<0.001
Per additional preterm delivery			1.22 (1.16, 1.28)	<0.001
30-43 years after first delivery
0 preterm	6,039	209.3	Reference
1 preterm	822	291.4	1.34 (1.25, 1.44)	<0.001
≥2 preterm	211	365.2	1.71 (1.49, 1.96)	<0.001
Per additional preterm delivery			1.30 (1.24, 1.36)	<0.001

^*Stroke incidence rate per 100,000 person-years.

^†Adjusted for maternal age (as Cox model time scale), year of delivery, parity, education, employment, income, region of origin, BMI, smoking, preeclampsia, other hypertensive disorders, and diabetes prior to delivery.