Spasmodic pain during dysmenorrhoea is attributed to:

Spasmodic pain is attributed to myometrial contractions, due to increased PGF2a, which is secreted under the effect of progesterone.. Note that progesterone is mainly secreted after ovulation, by the corpus leuteum. Therefore, whenever ovulation is absent (Anovulatory cycles), menstruation is not acconpanied by spasmodic pain (i.e., painless bleeding in anovulatory cycles) Congestive dysmenorrhoea is explained by pelvic venous congestion, which can be seen on Doppler ultrasound. Vasopressin and endothelin, by increasing PGF2a secretion also contribute to dysmenorrhoea. Ref: Shaw&;s textbook of Gynaecology 17th edition Pgno: 124