Monthly number of preterm births and environmental physical activity.

Unlabelled: Recent studies have reported links between external physical factors and human homeostasis.

Objective: to determine whether the monthly values of specific physical environmental factors are associated with the monthly number of preterm births in a major medical center in Israel.

Methods: The sample included 1006 infants weighing less than 1500g born live to 774 mothers during 96 consecutive months (1995-2002) at a tertiary medical center in Israel.