Strengths and limitations:
The strengths of this study are the study size, and the unbiased and random selection of the participants from all of Denmark, meaning that there was no selection for social status, income, race etc. All samples were handled in the same way, and analyzed in the same labouratory, thus minimizing analytic variance. We were not able to account for lifestyle factors associated with maternal request for CS or factors increasing the risk of CS. Further, we did not have any information regarding length of labour.