Clinical features

Why?

Oral contraceptive pill use, particularly if a smoker increases the risk of stroke

Outcome	Risk Factor	PEER	OR (95% CI)	NNH (95% CI)
first-ever stroke b	current user of oral contraceptives independent	0.1%	2.50 (1.50 to 4.00)	670 (330 to 2000)
	smokes and current user of oral contraceptives independent		2.90 (1.50 to 5.70)	530 (210 to 2000)
	ever used oral contraceptives independent		1.50 (1.10 to 2.00)	2000 (1000 to 10000)
	smokes and former user of oral contraceptives independent		1.80 (1.10 to 2.80)	1300 (560 to 10000)
	oral contraceptives with high progestogen content independent		6.70 (1.60 to 28.5)	180 (37 to 1700)
	oral contraceptives with high oestrogen content independent		5.80 (1.50 to 22.8)	210 (46 to 2000)
	oral contraceptives with intermediate progestogen content independent		3.60 (1.60 to 8.20)	380 (140 to 1700)
	oral contraceptives with intermediate oestrogen content independent		2.90 (1.70 to 5.00)	530 (250 to 1400)

Note:

• Hormone replacement therapy does not clearly increase the risk of stroke. ^d