US state legislatures have proposed laws prohibiting abortions after embryonic electrical activity is detectable—a development that typically occurs 6 weeks after the last menstrual period begins.

A missed period is often the earliest symptom of pregnancy, but irregular menstrual cycles can delay pregnancy detection past 6 weeks.

To assess differences in menstrual cycle irregularity by group, the researchers analyzed data from a commercial mobile-device app on 1.6 million menstrual cycles reported by 267,209 US women aged 18–39 years from 2014 to 2016.

The results suggest that 22% of women in the study experienced cycle irregularity, defined as consecutive cycles differing by an average of 7 or more days. Women aged 18–24 years had twice the risk of irregularity compared to women aged 35–39 years.

Women who reported polycystic ovary syndrome, type 2 diabetes, obesity, hormone irregularity, and thyroid dysfunction had significantly increased risk of irregular cycles. Hispanic women had 1.4 times the risk of irregular cycles as non-Hispanic Black women and 1.2 times the risk as non-Hispanic White women.

According to the authors, the findings suggest that menstrual irregularity imposes physiological barriers to abortion access under so-called “6-week” laws for a fraction of the US population for reasons beyond individual control. 

https://www.pnas.org/content/119/1/e2113762118

http://sciencemission.com/site/index.php?page=news&type=view&id=publications%2Fmenstrual-irregularity&filter=22