Oral contraceptive use increases the risk of subarachnoid haemorrhage (SAH), bleeding under the thin membrane which covers the brain and spine, according to a new meta analysis.
Although SAH was one of the earliest recorded risks of the birth control pill, it has not been an adverse effect which has received as much attention as, for instance, the risk of thrombosis. Nevertheless, analysis of 11 studies showed a relative risk of 1.42, indicating a significantly increased risk among oral contraceptive users.
Controlling for smoking and hypertension did not significantly alter the risk. Indeed, after excluding those studies that did not control for smoking, the risk of SAH increased with higher oestrogen doses to 1.94. Conversely, the risk was lower with lower doses of oestrogen.
SAH is still a rare occurrence, affecting only around 15 out of 100,000 women. Nevertheless, women with a known unruptured aneur ysm, a family history of the illness, smoking or hypertension might wish to consider other methods of contraception (Neurol, 1998; 51: 411-8).