Risk of arteriovenous malformation bleeding is eight times higher during pregnancy

A new study supports what neurosurgeons have long suspected—that pregnancy is an important risk factor for bleeding from arteriovenous malformations (AVMs) in the brain, reports the August issue of Neurosurgery, official journal of the Congress of Neurological Surgeons. The journal is published by Lippincott Williams & Wilkins, a part of Wolters Kluwer Health.

The best available data suggest that pregnant women with AVMs face an eight percent risk of rupture and bleeding during pregnancy—far higher than the risk in non-pregnant women. Based on their findings, Bradley A. Gross, MD, and Rose Du, PhD, of Harvard Medical School outline some recommendations for women with AVMs who want to have children or are already pregnant.

Risk of AVM Bleeding Is Eight Times Higher During Pregnancy
Drs. Gross and Du reviewed the records of 54 women with confirmed AVMs between 2002 and 2010. Arteriovenous malformations are tangled complexes of interconnected arteries and veins that are prone to rupture and bleeding, which can lead to death or serious disability.

The researchers calculated the total risk of bleeding AVMs in terms of the total number of "patient-years" at risk. They then assessed the risk of bleeding events during the total time their patients were pregnant. The 54 patients had a total of 62 pregnancies during follow-up. Four of the women had a total of five bleeding events while pregnant.

Based on the data, the researchers calculated an AVM bleeding risk of 8.1 percent per pregnancy, or 10.8 per year. By contrast, the rate of bleeding while the women were not pregnant was 1.1 percent per year.

Thus the risk of bleeding from an AVM was about eight times higher during pregnancy. On analysis of follow-up data to age 40, the risk of bleeding during pregnancy appeared even greater—18 times higher.

Neurosurgeons have long regarded pregnancy as a risk factor for bleeding AVMs. However, because ruptured AVMs are relatively rare, it is difficult to calculate the true risks.

Within the limitations of the data, the study strongly suggests that the risk of bleeding AVMs is substantially higher during pregnancy. In the authors' four cases, bleeding AVMs caused sudden headache and other symptoms between 22 and 39 weeks of pregnancy. With prompt treatment, all of the women and their infants survived (although one of the mothers was left with permanent disability).

Based on their findings, Drs. Gross and Du recommend treatment for any woman with an AVM who is considering having children—especially if they've previously had an episode of bleeding. If an unruptured AVM is discovered during pregnancy, they recommend "comprehensive patient counseling," discussing the risks of treatment versus "cautious continuation" of pregnancy without treatment.

When it's time for delivery, they recommend cesarean section. While noting that other doctors and hospitals may follow a different approach, Drs. Gross and Du hope their study and recommendations will "incite thought and invoke added caution in women with known, untreated AVMs planning to bear children."