Background: Combined Oral Contraceptive Pills (COCPs) are widely used. This study was carried out to determine prevalence rate of twin delivery and to assess the effect of combined oral contraceptive pills on twin delivery in the next pregnancy.

Materials and Methods: This was an epidemiological case control study. The study was under taken in Ahwaz in 1999-2001. Data was collected from both governmental and private hospitals. Cases were 156 pregnant women who attended to hospital for termination of twin pregnancy. Controls were also 156 women with singleton pregnancy who attended to hospital for delivery. Type of hospital, maternal age, gravida and history of twin pregnancy in the family were matched between cases and controls. Trained interviewers filled questionnaires. Other information such as weight of newborns was collected by observation.  Softwares such as Spss for windows, EPI and CIA (confidence interval analysis) were used for data analysis.

Results: The prevalence rate of twin delivery was 153/10000 live births.  There were significant difference between twin pregnancy and irregular menstrual cycle (p=0.04), problem in newborn (p<0.001), gestational age and husband’s job (p=0.006) Overall 29.8% of all cases had used oral contraceptive pills. The difference between two groups for use of contraceptives was significant (p=0.04).

Conclusion: Consumption of COCP is not associated with twin delivery in next pregnancy. Evaluation of other factors is recommended.