In the Tel Aviv region (approximately170km2), there were143,495 live-born infants, stillbirths and fetal deaths during the study period. We excluded births without information regarding gestational age or living in rural areas, and those who lived in a radius more than 10 km from an air monitoring station. A total of 135,527births met the study inclusion criteria. Of them 130,402 were births without congenital malformations