Table 3.

Prenatal use of aspirin by pregnant women and risk of miscarriage. Values are numbers (percentages) unless stated otherwise

	Miscarriage
Aspirin use	Yes (n=154)	No (n=848)	Hazard ratio (95% CI)*
Non-users (n=980)†	149 (15)	831 (85)	1.0
Users (n=22):	5 (23)	17 (77)	1.6 (0.6 to 4.1)
Gestational age at first use:
At conception (n=6)‡	3 (50)	3 (50)	4.3 (1.3 to 14.2)
After conception (n=14)	2 (14)	12 (86)	1.1 (0.3 to 4.5)
Duration of use:
≤1 week (n=16)	3 (19)	13 (81)	1.4 (0.4 to 4.5)
>1 week (n=5)	2 (40)	3 (60)	3.0 (0.7 to 12.9)

^*Adjusted for previous miscarriage, education, maternal age, gravidity, race, use of Jacuzzi or hot tub, multivitamin use, and smoked since last menstruation. Further adjustment for other variables listed in table 1 did not change the results.

^†Used neither NSAIDs nor aspirin.

^‡Within the first week of gestational age.