Future dairy cows are conceived during the maternal lactation, a productive period characterized by a large demand for energy and nutrients. Indeed, during this period embryo and foetal development closely compete with the large metabolic requirements of mammary gland for milk production. Supplementing extruded linseed (EL), a feed rich in n-3 fatty acids, to pregnant dairy cows may help to enhance their performance and to prevent negative metabolic imbalances. This retrospective study investigated whether the reproductive performance of primiparous cows is affected by the environment of their dam during pregnancy. To investigate the potential dose-effect relationship during pregnancy, we defined a proxy of EL intake per day by using deliveries of EL based feeds from 22 companies in the study period 2008-2015 in France. Based on recommendations for EL, use on the fields, 2 levels of exposures of the dam during the first pregnancy semester were created: low [<300] (n=7,186 AIs) and high [>300] (=10,845 AIs) g/cow/d. The reference population was composed of primiparous cows issued from pregnant dams that did not receive EL in the same herds than exposed dams (n=25,557 AIs). Mean daily EL intake in exposed pregnant dams population was 324 g/cow/d (+-226.1). Reproductive performance was studied on 43,588 AIs from 1,042 herds and 29,335 primiparous cows using Cox models for days to first AI and days to conception, and logistic regression models for risk of return-to-service, adjusted for factors likely to influence the reproductive performance and for a herd random effect. Risk of return-to-service between 18 and 78 days after first and second AI did not differ between cows issued from exposed dams or from reference dams. Days to first AI was significantly reduced in cows from exposed dams, whatever the exposure level (HR: 1.09 for the low EL level and HR: 1.08 for the high EL level). The effect was the same for time from calving to conception (HR: 1.10 for the low EL level and HR: 1.07 for high EL level). This original large-scale epidemiological study provides new insights into potential epigenetic effects of feeding EL during the foetal development of dairy cows