Why does pregnancy increase the risk of stroke?
One cause is evolutionary. Historically, and still to this day, one of the biggest risks for maternal mortality is postpartum hemorrhage (bleeding) when you give birth, so our bodies have evolved to be very good at stopping bleeding. This can lead to an increased risk of developing blood clots. Rarely, this can lead to an ischemic stroke, where there is blockage of a blood vessel in the brain due to a blood clot.
The other major risk factor for maternal stroke is having hypertensive disorders of pregnancy, which are very, very common. Hypertensive disorders of pregnancy are when you develop elevated blood pressure in pregnancy or postpartum, so conditions like gestational hypertension, preeclampsia, or eclampsia. Even a healthy pregnancy puts a lot of strain on the heart and blood vessels, so having very high blood pressure adds to the strain on your arteries, and in extreme cases can cause them to burst. This is called a hemorrhagic stroke, and is a very dangerous form of stroke that is more likely to be fatal than an ischemic stroke.
What is the likelihood for stroke in pregnancy and postpartum?
Research has found that the risk of stroke is about 30 strokes per 100,000 deliveries, so it is overall a very low risk. In some groups — for instance, those with existing risk factors like chronic hypertension, heart conditions or genetic conditions that make them more likely to get blood clots — the risk might be higher during pregnancy, but generally it is not a common occurrence.
Pregnancy can be a time of high anxiety, so I don’t want to worry new mothers. However, being aware that stroke is a risk, being aware of the highest-risk time period, and being aware of the warning signs is important.
What are the stroke warning signs people should look out for during and after pregnancy?
I’m always concerned when people report they have a new or very severe headache, especially around that time of delivery or postpartum. Having migraines is actually a risk factor for developing preeclampsia, and it’s also a risk factor for stroke, so even if you have had headaches in the past, you should watch out for signs that this headache is different and might be more than just a migraine. If your headache is worse lying down than it is standing up, it’s a big red flag, because in general, a migraine usually gets better if you lie down in the dark in a quiet room. If you lie down flat and your headache becomes unbearable, that can be a sign of a blood clot. And if you have a headache coupled with high blood pressure, that’s a red flag.
And of course, watch out for any of the typical signs of a stroke — numbness or tingling on one side, a droopy face, or slurred speech, or vision changes like loss of vision or double vision. We sometimes use the BE FAST mnemonic, which is Balance, Eyes, Face, Arm (weakness), Speech (difficulty or slurred), and then it’s “Time to call 911” because the quicker you get treated for stroke, the better the outcome. Time is brain!