BACKGROUND: The hemorrhage risk of unruptured and untreated cerebral arteriovenous malformations (AVMs) has been shown to be higher for female patients than male patients in their child bearing ages. Although it has been neurosurgical practice to advise female patients in their childbearing ages to postpone pregnancy until proven AVM obliteration, there is no literature consensus regarding this potential hemorrhage risk increase. OBJECTIVE: To accurately quantify the risk increase for AVM hemorrhage during pregnancy. METHODS: This study is based on data from previous publications, consisting of known age at the first AVM hemorrhage in 3425 patients. The risk increase during pregnancy could be calculated from the difference in age distribution for the first AVM hemorrhage between male patients and female patients, taking the average pregnancy time per female into account. A comparison was also made with data for all hospital discharges (13 751) in Germany 2008 to 2018 with the diagnosis brain AVM. RESULTS: The average pregnancy and puerperium time was 1.54 years per female in the patient population, which was used to determine the annual AVM hemorrhage risk during pregnancy to be around 9%. The increased risk during pregnancy was further evidenced by analysis of a subgroup of 105 female patients, for which pregnancy status at the time of hemorrhage was known. CONCLUSION: The quantified annual risk for AVM hemorrhage during pregnancy is about 3 times higher than that of male patients at corresponding age. This provides an important basis for advising female patients with patent AVMs about the increased risk for hemorrhage that a pregnancy would entail.