Background: The interpregnancy interval (IPI) the time between a live birth and conception of the subsequent pregnancy is a critical, yet modifiable, determinant of maternal and perinatal outcomes. Both excessively short and prolonged IPIs have been linked to increased risks of obstetric complications, yet limited data exists in localized settings to guide optimal birth spacing. Objectives: To evaluate the association between interpregnancy interval and fetomaternal outcomes among pregnant women, and to identify the interval range associated with the least complications.

Methods: This hospital-based prospective observational study was conducted at the Department of Obstetrics and Gynecology at tertiary care hospital, from June 2023 to May 2024. A total of 360 pregnant women with gestational age ≥28 weeks and singleton pregnancies were included. Women were categorized into three groups based on IPI: short (<18 months), optimal (18–59 months), and long (>59 months). Data on demographic, clinical, maternal, and fetal outcomes were collected and analyzed using Chi-square test and odds ratios. A p-value <0.05 was considered statistically significant.

Results: Short IPI (<18 months) was significantly associated with increased incidence of maternal anemia (66.67%), preterm labor (up to 33.33%), fetal growth restriction (FGR, up to 46.67%), and low birth weight. Long IPI (>59 months) showed increased rates of preeclampsia (39.58%), gestational diabetes (18.75%), and placental complications. The lowest complication rates were observed in the optimal IPI group (18–59 months). The association of IPI with FGR, anemia, and hypertensive disorders was statistically significant (p < 0.0001).

Conclusion: Both short and long interpregnancy intervals are associated with increased maternal and fetal complications. Optimal spacing of 24–59 months was associated with the most favorable outcomes. Counseling on birth spacing and postpartum contraception should be integral to antenatal and postnatal care strategies to improve maternal and neonatal health.