Background: It is important when conducting epidemiologic studies to closely monitor lost to follow up (LTFU) rates. A high LTFU rate may lead to incomplete study results which in turn can introduce bias to the trial or study, threatening the validity of the findings. There is scarce information on LTFU in prospective community-based perinatal epidemiological studies. This paper reports the rates of LTFU, describes socio-demographic characteristics, and pregnancy/delivery outcomes of mothers LTFU in a large community-based pregnancy registry study. Methods: Data were from a prospective, population-based observational study of the Global Network for Women's and Children's Health Research Maternal Newborn Health Registry (MNHR). This is a multi-centre, international study in which pregnant women were enrolled in mid-pregnancy, followed through parturition and 42 days post-delivery. Risk for LTFU was calculated within a 95%CI. Results: A total of 282,626 subjects were enrolled in this study, of which 4,893 were lost to follow-up. Overall, there was a 1.7% LTFU to follow up rate. Factors associated with a higher LTFU included mothers who did not know their last menstrual period (RR 2.2, 95% CI 1.1, 4.4), maternal age of < 20 years (RR 1.2, 95% CI 1.1, 1.3), women with no formal education (RR 1.2, 95% CI 1.1, 1.4), and attending a government clinic for antenatal care (RR 2.0, 95% CI 1.4, 2.8). Post-natal factors associated with a higher LTFU rate included a newborn with feeding problems (RR 1.6, 94% CI 1.2, 2.2). Conclusions: The LTFU rate in this community-based registry was low (1.7%). Maternal age, maternal level of education, pregnancy status at enrollment and using a government facility for ANC are factors associated with being LTFU. Strategies to ensure representation and high retention in community studies are important to informing progress toward public health goals.