Human fertility is closely tied to birth intervals, which consist of postpartum amenorrhoea (PPA), waiting time to conception, and gestation. While gestation is relatively constant, PPA – the period between the end of pregnancy and the return of ovulation – varies significantly, influenced by factors such as breastfeeding practices and socio-economic conditions. This study aims to analyse these components of birth intervals in rural Manipur, India, focusing on variations in PPA, waiting time to conception, and their interactions with socio-demographic factors. A cross-sectional survey of 1171 women was conducted, with data analysed using Cox regression models. Key findings indicate that extended breastfeeding significantly prolongs PPA, while infant mortality and family income also impact PPA duration. Waiting time to conception is influenced by infant mortality, the sex of the previous child, desired number of sons, lactation duration, and the wife’s education level. Higher family income and longer lactation were associated with longer waiting times, while a deceased previous child and son preference reduced waiting time. The study reveals that socio-economic factors, including income and education, play a critical role in determining birth intervals, while religious differences also affect reproductive outcomes. These findings highlight the complex interplay of physiological, socio-economic, and cultural factors influencing fertility. The results emphasize the need for targeted interventions addressing these variables to better manage fertility and improve reproductive health outcomes.