Objective: To compare effect of Omega 3 fatty acid supplementation versus no supplementation in high risk pregnant females from 20 weeks gestation in terms of frequency of preterm delivery. Methods: We conducted a prospective randomized controlled clinical trial in department of Obstetrics and Gynecology and, Railway Teaching Hospital Islamic International Medical College Trust, from January 2015 to Jan 2017. Women with a history of prior spontaneous singleton preterm birth and a current singleton gestation were divided into two groups A and B by computer generated random numbers. Omega 3 fatty acid supplementation was given to group A patients from 20 weeks to 36 weeks gestation and patients in group B was received no such treatment. Frequency of preterm delivery was compared among patients of both groups. Results: A total of 500 women with singleton pregnancy with history of one or more preterm deliveries were included, and none was lost to follow up. The mean duration of pregnancy at delivery between the omega3 supplemented and control groups [38.2 (SD, 0.6) weeks and 36.6 (SD, 0.9) weeks, P<0.0001 respectively] was statistically different. The data were also analyzed for birth weight and statistically significant difference of the weights were found in the two groups [3.2 (SD, 0.233) and 2.8 (SD, 0.259) controls P <0.0001]. Conclusion: In this study we found that gestational age and birth weight, both are significantly improved with oral administered omeg-3 in high risk pregnancy when compared with controls.