Objective: Women and their infants need special protection in war context, as traumatic events can risk maternal mental and obstetric health and compromise infant development. This prospective study examined, first, how exposure to war trauma is associated with maternal mental health in pregnancy and postpartum, obstetric and newborn health, and infant development. Second, it tested the role of maternal mental health and obstetric risks in mediating between war trauma and infant development. Method: Palestinian women (N = 511) from the Gaza strip participated during pregnancy (T1) and at 4 (T2) and 12 (T3) months postpartum. They reported PTSD, depressive, anxiety, and dissociative symptoms, as well as pregnancy complications, newborn health risks such as prematurity, and infant sensorimotor and language development. Results: First, exposure to war trauma was associated with high levels of maternal mental health and complications at pregnancy, and with increased postpartum mental health symptoms, but exposure was not directly associated with newborn health risks or problems in infant development. Second, maternal mental health both in pregnancy and postpartum, but not pregnancy complications or newborn health, mediated the negative impact of war trauma on infant sensorimotor and language development at 12 months. Conclusion: Interventions to protect early child development in war conditions should be tailored to support maternal mental health.