Longitudinal cohort studies are important for the understanding of etiological mechanisms of underlying hypotheses. However, it is particularly challenging to sustain participation of subjects in follow up visits in birth cohorts, as the observation period spans over several years, making it vulnerable to lose tracking subjects for several reasons. These include change in location of residence and lack of interest in the later stages of the study. In India, the traditional practice of pregnant women leaving the study area to return to their maternal residence for delivery. Few groups belonging to ethnic minorities, with low family income or low education can be at higher risk of selective attrition. In the absence of high follow-up rate, the results from prospective cohort studies are can be biased. Such a bias can occur if the reason for the loss is related to the outcome under investigation. The cohort studies done in India have variable rates of loss to follow-up varying from, 14-82%. The barriers for retaining greater proportion of study participants can be due to several reasons. While a number of reviews have reported different ways of improving study participation, little is known about the effectiveness of specific retention strategies deployed in retention of mothers and infants in a birth cohort.

The proportion of pregnant women turning up for regular antenatal health checkups is poor in India. This is due to several reasons including lack of awareness, lack of social support, long waiting time, financial constraints and fear of hospital care. Evidence suggests that maternal education, husband's education, marital status, availability, cost, household income, women's employment, media exposure and previous obstetric history affects uptake of antenatal care services. According to National Family Health Survey (NFHS) (2014-15), only 55.5% of women in urban Bangalore had completed the required four antenatal care visits during pregnancy.

MAASTHI (Maternal Antecedents of Adiposity Studying the Transgenerational role of Hyperglycaemia and Insulin) is a prospective birth cohort with the aim of assessing the effects of glucose levels in pregnancy on the risk of adverse infant outcomes, especially in predicting the possible risk markers of later chronic diseases. The recruitment of the pregnant women in MAASTHI has begun in the month of April 2016. Of the eligible pregnant women only 77% completed the oral glucose tolerance tests despite offering the test free of cost and repeated reminders by the research team to get tested for gestational diabetes. After completion of OGTT, the follow ups of mother and child are conducted at birth and annually during the year 1, 2, 3 and 4 of the child. Despite stringent adherence of including only the residents of the source population, nearly 13% of the women were lost to follow-ups at birth. These women delivered in a different hospital mostly due to obstetric complications. Currently around 80 participants are recruited per month, with completion of all their records, anthropometry measurements, and Oral Glucose Tolerance Test (OGTT). Once the OGTT is done between 24-32 weeks of gestation, there is no further opportunity to meet them again till the delivery. The duration without contact increases the likelihood for attrition of future follow-ups. In the intervening period of initial contact and follow-up's, it is important that the research staff constantly engage with the participants through innovative methods. In order to improve the number of women undergoing OGTT and follow-ups, an intervention trial will be carried out that examines the role of innovative 1) IVR and 2)Mother and baby workshops during the intervening time period between baseline and follow-up.