Partial Rupture Syndrome (PRS)

Partial Rupture Syndrome (PRS) is an ovulation disorder in which the follicle begins to open but never fully collapses.¹ The follicle becomes smaller at the expected time of ovulation. It does not empty. A small cyst-like space remains. The egg and its surrounding cells are not fully released.

Dr. Thomas W. Hilgers defined PRS as its own ultrasound finding within the NaProTechnology follicle maturation study.¹ Trained sonographers make the diagnosis. They compare a series of ultrasound scans taken around the time of ovulation. The follicle shrinks, but it never empties. This pattern sets PRS apart from a normal ovulation. It also sets PRS apart from the other rupture disorders in this system. No single size in millimeters, and no set number of hours, defines the diagnosis on its own.

PRS belongs to Hilgers' sonographic classification of ovulation disorders. In Luteinized Unruptured Follicle Syndrome, the follicle never opens at all. In Delayed Rupture Syndrome, the follicle opens fully, but later than expected. Empty Follicle Syndrome asks a different question. It asks whether the cumulus oophorus, the cluster of cells that holds the egg, can be seen inside the follicle before it opens. Sonographers check for it on the same scan. It can appear with PRS, with a normal ovulation, or with any other pattern in the group.

A follicle that opens only partly forms a weaker corpus luteum. The corpus luteum is the tissue that makes progesterone after ovulation. A weaker corpus luteum makes less progesterone in the second half of the cycle. The chance of pregnancy in that cycle falls, even when the cycle chart looks normal. Serial ultrasound in a follicle maturation study identifies the defect. Charting alone cannot tell PRS apart from a normal ovulatory cycle.