Use of cannabis during pregnancy is on the rise, yet little is known about how women administer cannabis during the perinatal period. This study examined self-reported modes of cannabis administration among women in the year before and during pregnancy, and their association with self-reported cannabis use frequency using data from 585 women screened in 2018-2019 for cannabis use during standard prenatal care in two medical centers in Northern California. The prevalence of cannabis use was 12% before pregnancy and 3% during pregnancy. Among the 71 women who reported cannabis use before pregnancy and the 19 women who reported cannabis use during pregnancy, smoking was the most common mode of administration (58% and 42%), followed by edibles (27% and 16%), vaping (23% and 16%), lotions (11% and 5%), and other (10% and 0%). In the year before pregnancy and during pregnancy, monthly or less use was most common (56% and 58%), followed by weekly use (24% and 26%) and daily use (20% and 16%). Among cannabis users, 43% used more than one mode before pregnancy compared to 15% during pregnancy. Daily cannabis use was most common among women who reported smoking only or smoking in combination with other modes. These novel results indicate that while smoking is the most common mode of cannabis administration during the perinatal period, there is variation in use and co-use of alternative modes. Future studies are needed to understand the relative health effects associated with individual and combined modes of cannabis administration during pregnancy.