General Background The anatomy in the groin area differs between men and women. This has been shown to significantly impact outcomes after surgery for groin hernias (1,2). Since women more often have concomitant inguinal and femoral hernias, techniques that provide access to the preperitoneal area are thus recommended for hernia repairs in women (3). This should, however, be reconsidered for nulliparous women if they do not have an increased risk of femoral hernias. In a previous study, we showed that women face a higher risk of recurrence than men after primary ventral hernia repair (4). Whether this is due to the inherent anatomy of the abdominal wall in women or to previous pregnancies remains unclear (5). There are also reasons to believe that the anatomy varies between women. It is well known that hormonal changes and distension affect the abdominal wall during pregnancy, but few studies have examined the impact of pregnancy on the groin anatomy. Femoral hernias are considered to be rare in nulliparous women, but there are no epidemiological studies confirming this. Pregnancies can also affect the development of direct and indirect hernias. Aims and hypthesis The aim of the present study is to analyse the association between parity and risk of hernias. If the study shows an association between parity and the risk of developing inguinal, femoral and primary ventral hernias, this may have an impact for the choice of method of repair in women. These issues can only be solved with large population-based studies with sufficient time of follow-up. If the recurrence rate increases with parity, this indicates that parity should be taken into account when deciding on mesh reinforcement in ventral hernia surgery Methodology The study will be based on the Swedish Mammography cohort. The incidence of groin hernias and primary ventral hernias in nulliparous and multiparous women will be compared in a nested case-control study of women who have undergone hernia surgery versus those who have not. The risk of developing recurrent hernias will be analysed in Cox proportional hazard analysis, by analysing recurrent hernia repairs following the first registered umbilical hernia repairs, adjusting for age and method of repair at the primary repair.