Other confounding conditions contributing to ORS are thick and profuse pelvic adhesions, inflammation, bleeding after surgery (peri-operative bleeding), and ovaries which are retroperitoneal, can all contribute to the unintentional preservation of ovarian fragments. Risks
The risk of ovarian remnant (ORS) is increased by incomplete removal of the ovary at the time of oophorectomy. Surgical factors that contribute to incomplete removal include those that limit surgical exposure of the ovary, or compromise surgical technique. Factors may include:

adhesions – these can limit visualization of the ovary and may also cause it to adhere to surrounding tissues. Adhesions are often present due to preexisting conditions and/or prior surgeries. In the majority of cases reported since 2007, endometriosis was the most common indication for the initial oophorectomy in patients who subsequently had ORS. Endometriosis increases the risk for functional ovarian tissue being embedded into adjacent structures, making complete excision of tissue challenging. Anatomic variations - unusual location of ovarian tissue, for example
Intraoperative bleeding
Poor surgical technique – this may include failure to obtain adequate exposure or restore adequate anatomy, or imprecise choice of incision siteOvarian remnant (ORS) may first be considered in women who have undergone oophorectomy and have suggestive symptoms, the presence of a mass, or evidence of persistent ovarian function (by symptoms or laboratory testing). A history of oophorectomy is required, by definition, to make the diagnosis. Notes regarding the indication for the procedure and the procedure itself should be reviewed and may include prior abdominal or pelvic surgery, endometriosis, and/or poor surgical visualization.
Due to a greatly increased price, a pricing controversy occurred in this country. OHPC was previously available at low cost from compounding pharmacies in the United States, but this became prohibited in 2016. Medical uses
Preterm birth
The use of OHPC in pregnancy to prevent preterm birth in women with a history of preterm delivery between 20 weeks and 36 weeks and 6 days is supported by the Society of Maternal Fetal Medicine Clinic Guidelines put out in May 2012 as Level I and III evidence, Level A recommendation. Level I evidence refers to a properly powered randomized controlled trial, and level III evidence is support from expert opinion, while a Level A recommendation confers that the recommendation is made based on good and consistent scientific evidence. OHPC 250 mg IM weekly preferably starting at 16–20 weeks until 36 weeks is recommended. In these women, if the transvaginal ultrasound cervical length shortens to <25 mm at < 24 weeks, cervical cerclage may be offered. In the 2013 study the guideline recommendation is based on, there was also a significant decrease of neonatal morbidity including lower rates of necrotizing enterocolitis (0 in the treatment group vs 4 in the control), intraventricular hemorrhage (4 in the treatment group compared with 8 in the control for a relative risk of 0.25), and need for supplemental oxygen (14% in the treatment group vs 24% in the placebo for a relative risk of 0.42). Furthermore, this study contained 463 women, 310 of whom received injection.