Strengths and limitations
The study was conducted in one single tertiary hospital with smaller sample size. We did not record the pregnancy outcomes like preterm deliveries and the subtypes of PE among those who developed PE. So, the values observed here may not be comparable with the one observed in primary and secondary level settings. Also, the dropout is high in each trimester because most of the pregnant women got registered during the first trimester later moved out of the city to their mother’s home for delivery. Despite the limitations, this is the first longitudinal study of its kind in Indian settings with regular follow-up of once in each trimester till delivery to measure the incidence of PE in the high-risk population. Selection bias was minimized by using the nested case-control study design compared to the traditional case-control study.