Neurosurgeons have long suspected that pregnancy is an important risk factor for bleeding from arteriovenous malformations (AVMs) in the brain, but now their beliefs are supported by a new study published in the August edition of Neurosurgery, which reveals that the risk of pregnant women with AVMs sustaining a rupture and bleeding during pregnancy is a significant 8% higher to that of non-pregnant women.

AVMs are tangled complexes of interconnected arteries and veins that are prone to rupture and bleeding, which can lead serious disability or death.

The findings have prompted Harvard Medical School specialists Bradley A. Gross, MD, and Rose Du, PhD, to draw up some recommendations for pregnant women with AVMs and for those who plan to have children.

Drs. Gross and Du reviewed 54 women’s records who were diagnosed with AVMs between 2002 and 2010, calculating the total risk of bleeding AVMs for the total number of “patient-years” at risk. They established a total of 62 pregnancies amongst the 54 patients and investigated the risk of bleeding events during all the women’s entire pregnancies, establishing that 4 women had a total of five bleeding events during their pregnancy.

Calculations based on this data revealed an AVM bleeding risk of 8.1% per pregnancy, or 10.8% per year, compared with a 1.1% per year rate of bleeding when the women were not pregnant. The results translate into an eight times higher risk of bleeding from an AVM during pregnancy. A follow-up until the age of 40 revealed an even greater risk, i.e. 18 times higher during pregnancy.

Even though neurosurgeons have long believed that pregnancy is a risk factor for bleeding AVMs, incidents are relatively rare and therefore it is difficult to calculate the exact risks.

Although the study was limited due to its small patient population, the results nevertheless strongly indicate a substantially higher risk of bleeding AVMs during pregnancy. Amongst the 4 incidents of the study participants, bleeding AVMs led to sudden headache and other symptoms between week 22 and 39 of their pregnancy, although all women and infants survived due to prompt treatment. Unfortunately, one of the mothers was left with permanent disability.

The results prompted Drs. Gross and Du to recommend that any women with an AVM, who considers having children, should get treatment, particularly those with previous episodes of bleeding. In cases where an unruptured AVM is discovered during pregnancy, they recommend “comprehensive patient counseling,” to discuss the risks of treatment compared with “cautious continuation” of the pregnancy without treatment.

The team recommends delivery by cesarean section, and note that medical professionals or institutions may suggest a different approach. However, they hope that their findings and recommendations will “incite thought and invoke added caution in women with known, untreated AVMs planning to bear children.”

Written by Petra Rattue