Background: With respect to the prevalence of short-interval pregnancy in our country and also lack of information data in Kashan, the present study was conducted in Kashan to determine the prevalence of short-interval pregnancy and also its association with birth height and weight.

Materials and Methods: A descriptive study was carried out to determine the prevalence of short-interval pregnancy whereas a historical cohort study was performed of determine its association with birth height and weight. Our case group consisted of two groups: 150 mothers with interval of less than 15 months and 90 mothers with interval of less than 12 months, between their pregnancies. 150 mothers with adequate interval between pregnancies were Surveyed in cone and control groups and analyzed by t-test. Relative and absolute risks of short-interval pregnancies were determined for birth weight of less 3000gr and birth height of less 49cm.

Results: Of 2300 mothers, 216 (94%) had short-interval pregnancy. Results have revealed that there is no association between interval of less than 15 mothers and birth height and weight, however of less than 12 months and birth height and weight. The mean (±SD) of birth weight was 3356±443 and 3237±430 gr in the control and case group (Interval <12 months), respectively (P<0.05). Meanwhile, their birth height was 50.4±2 and 49.7±1.8 cm, respectively. The RR of weight <3000gr was 105 and for height <49 was 2.1. The AR for these values were 0.5% and 16.5%, respectively (P<0.05%).

Conclusion: Pregnancy with interval of less than 12 months is associated with lower birth and weight. Further studies are highly suggested.