Tehran University of Medical Sciences Journal of Family and Reproductive Health 1735-8949 10 2 2016 08 23 85 91 EN Seyedeh Neda Mousavi Department of Biochemistry and Nutrition, School of Medicine, Zanjan University of Medical Sciences, Zanjan, Iran Fariba Koohdani Department of Cellular Molecular Nutrition, School of Nutritional Sciences and Dietetics, TehranUniversity of Medical Sciences, Tehran, Iran Farzad Shidfar Department of Nutrition, School of Health, Iran University of Medical Sciences, Tehran, Iran Leila Shafiei-Neek Department of Sport Physiology, School of Physical Education and Sport Sciences, University of Tehran, Tehran, Iran 2016 02 12 2016 05 23 Objective: Maternal type and amounts of dietary fatty acids affect on reproductive process in the mice. The present study investigated the effects of maternal supplementation with different amounts of omega-6 or omega-9 during pregnancy on the number of offspring, sex-ratio and duration of gestation. Materials and methods: Eight-week-old female C57BL/6 mice were randomly assigned into four dietary groups including low omega-6 (16%; LO6), low omega-9 (16%; LO9), high omega-6 (45%; HO6) and high omega-9 (45%; HO9) during gestation. Number of offspring, sex-ratio and duration of pregnancy were compared among four dietary groups. Results: There was significant difference between LO6 and HO6 (p < 0.0001), LO9 and HO9 (p < 0.0001) groups in total number of pups. The number of female and male offspring were significantly different between LO6 and LO9 (p = 0.009 and p = 0.001, respectively), LO9 and HO9 (p = 0.01 and p = 0.025) groups. Duration of pregnancy was significantly higher in low fat diet than high fat diet groups (< 0.001). Conclusion: High fat diet reduced number of pups, gestation duration and lead to early labor. Omega-9 fatty acids shifted sex of offspring to females. https://jfrh.tums.ac.ir/index.php/jfrh/article/view/394 https://jfrh.tums.ac.ir/index.php/jfrh/article/download/394/355