Background: At the time of marketing, knowledge on the safety of the use of drugs during pregnancy is still limited, as pregnant women are not included in pre-marketing research. Also after marketing, collecting information on drug use during pregnancy can be bothersome. In 2013 the pREGnant project started in order to develop and implement a national register for medical drug use during pregnancy in the Netherlands. This register will be used for signal detection and conducting epidemiological studies. In February 2014, a pilot study was started to test and validate this register. Objectives: To describe the first results of the pilot phase of the pREGnant register. Methods: In pREGnant, exposure to medical drugs and other potential risk factors are monitored prospectively. Data are collected by means of web-based questionnaires and completed by pregnant women, focusing on medical drug use, the health of the pregnant woman, pregnancy complications and outcomes, and the health of the child. In the pilot phase, different schemes for data collection are introduced in order to choose the best practice for inclusion. During the pilot phase, inclusion takes place at midwiferies and hospitals. Results: The method and approaches applied will be discussed as well as the number and type of inclusions. Based on the initial results of the validation studies and the experiences with implementing data from other data sources, possibilities for the definite system for pREGnant be discussed. Conclusions: The current lack of knowledge on the teratogenic risks of many medical drug use often hampers healthcare professionals in making evidencebased decisions on whether or not the beneficial effects of treatment outweigh the possible risks for the developing foetus and the pregnant woman. The pREGnant register will enable a systematic collection of information and may fill this gap of knowledge.