Summary

At mid-cycle, uterine contractions are predominantly cervical-fundal (from the bottom of the uterus to the top), specifically toward the fallopian tubes. The amplitude and frequency of the contractions increase significantly as ovulation approaches. There is evidence that this facilitates sperm ascension towards the distal (far) end of the fallopian tubes, where fertilization occurs. Women with endometriosis display marked uterine hyperperistalsis that differs significantly from the contractions of women without endometriosis. At mid-cycle, uterine contractions in women with endometriosis became dysperistaltic (abnormal), arrhythmic, and convulsive, while in controls, peristalsis continues to show long and regular cervical-fundal (normal) contractions. This may explain the high incidence of infertility even in women with only mild endometriosis.