Epidemiology and Clinical Implications of Twin and Multiple Pregnancies in Southeastern Iran: A Historical Cohort Study

Background: The incidence of twin and multiple pregnancies varies globally, influenced by genetic, environmental, and technological factors. Limited data are available from southeastern Iran, a region with distinct demographic and healthcare characteristics. Objectives: The present study aimed to determine the prevalence and associated factors of twin and multiple pregnancies among women who delivered at Ali-Ibn-Abi-Talib Hospital in Zahedan from 2015 to 2018. Methods: In this historical cohort study, all documented cases of twin and triplet deliveries were included through a complete census of hospital records. Only records with complete information on maternal age, parity, family history, mode of delivery, and type of conception (spontaneous vs. assisted) were analyzed to minimize selection bias. Data were extracted from standardized medical records and cross-verified by two independent reviewers. Descriptive statistics were performed to summarize variables using SPSS software (version 26). Results: Out of 25,425 deliveries, 267 (1.0%) were multiple pregnancies — 94.75% twins and 5.25% triplets. The highest rate of twin births occurred in the fourth pregnancy (31.2%), while triplet pregnancies were more common in primiparous women (42.9%). Women aged 21 - 30 years accounted for the highest prevalence of multiple pregnancies. Cesarean delivery was predominant (75%), especially in triplet cases (80%). Only 14% of cases had a positive family history, and assisted reproductive technology (ART) use was minimal (0.8%). Conclusions: Multiple pregnancies accounted for 1% of all births in this cohort, with spontaneous conception being predominant. Maternal age and parity were significantly associated with multiple gestations, while family history and ART use had limited influence. These findings emphasize the need for region-specific prenatal care strategies to improve outcomes in multiple pregnancies. Future studies should explore genetic, environmental, and hormonal factors influencing these pregnancies, and policymakers should prioritize tailored prenatal care for multiple pregnancies to mitigate associated risks.