Background: Maternal health is a public health priority in many African countries, but little is known about herbal medicine use in pregnancy. This study aimed to determine the pattern of use of herbal medicine in an urban setting, where women have relatively high access to public healthcare. Methods: This cross-sectional study included 333 women attending a childcare clinic in a district public health hospital in Nairobi, Kenya, during January and February, 2012, and who had delivered a baby within the past 9 months. Qualitative and quantitative data on herbal medicine use during their latest pregnancy were collected through an interviewer-administered questionnaire. Data was analysed descriptively and the Chi square test and Fishers’ exact test used to analyse relationships among variables. Results: About 12% of women used herbal medicine during their most recent pregnancy. The use of herbal medicine was associated with a lower level of education (p = 0.007) and use before the index pregnancy (p <0.001). Only 12.5% of users disclosed such use to healthcare professionals, and about 20% used herbal medicine concomitantly with Western medicine for the same illness/condition. Women used herbal medicine for back pain, toothache, indigestion and infectious diseases, such as respiratory tract infections and malaria. A proportion of users took herbal medicine only to boost or maintain health. There were high rates of self-prescribing, as well as sourcing from family and friends. Beliefs about safety and efficacy were consistent with patterns of use or non-use, although both users and non-users were unsure about the safety and contraindications of Western medicine during pregnancy compared with that of herbal medicine. Conclusion: Herbal medicine is used by 12% of pregnant women with access to healthcare in an urban context in Kenya, and often occurs without the knowledge of healthcare practitioners. Healthcare professionals should play a role in rational use of both herbal and Western medicine, by discussing contraindications and the potential for drug-herb interactions with patients. More studies are needed into the use of herbal medicines during pregnancy, labour and the postpartum period in different geographical areas, and into the health outcomes associated with their use.