According to a study published in the International Journal of Clinical and Experimental Pathology, progesterone-induced menses may have a negative effect on intra-uterine insemination (IUI) success. Researchers evaluated 241 IUI cycles from 2011 to 2012 and compared the results of 57 control cycles with results from 184 cycles with progesterone-induced menses.

Progesterone-induced menses resulted in thinner endometrium compared to the control group. Researchers noted no statistical differences between groups in terms of pregnancy rate and live birth, but concluded a possible effect as peak endometrial lining was compromised in the progesterone-induced group.

The endometrial lining is the blood-rich environment where a fertilized egg implants in the uterus. Optimal thickness is associated with improved pregnancy rates, thus progesterone-induced menses (endometrial withdrawal) may negatively affect pregnancy rates and live births.

Source: Dong X, Zheng Y, Liao X, Xiong T, Zhang H. Does progesterone-induced endometrial withdrawal bleed before ovulation induction have negative effects on IUI outcomes in patients with polycystic ovary syndrome? Int J Clin Exp Pathol. 2013 May 15;6(6):1157-63. Print 2013.