Ovarian hyperstimulation syndrome (OHSS) is the most serious iatrogenic complication of ovulation induction. The ovaries are noted to have a significant degree of stromal edema, interspersed with multiple hemorrhagic follicular and theca-lutein cysts, areas of cortical necrosis, and neovascularization. Mutations in follicle-stimulating hormone (FSH) receptors could be activating, resulting in OHSS, or inactivating, resulting in sterility. Bone morphogenic protein-15 (BMP-15) appears to be associated with mechanisms of infertility and superfertility in a dosage-sensitive manner. Human chorionic gonadotropin increases vascular endothelial growth factor (VEGF) production by granulosa cells and endothelial cells, which results in increased vascular permeability. Increased intraovarian blood flow and low intravascular ovarian resistance are correlated with the severity of OHSS in patients who develop the syndrome. The medical treatment of OHSS consists of correction of circulatory volume and electrolyte imbalance. Ultrasonographic guidance of transvaginal or transabdominal aspiration of ascites improves the symptoms of patients with OHSS.

With the advancement of ultrasound (US) technology with introduction of 3D technology as well, detailed examination of the uterine cervix, anatomy, and accurate measurements have become possible. Benign gynecologic conditions seen by US in non-pregnant state include nabothian cysts, cervical polyps, fibroids and Mullerian anomalies. The importance of transvaginal US in diagnosing placenta previa lies also in the ability by transvaginal US to determine exact distance of placental edge from internal os, which will consequently determine mode of delivery. US is the main diagnostic tool for cervical pregnancy. Doppler is a very important tool as well, due to its difficult diagnosis, it should be differentiated from the cervical stage of spontaneous abortion and nabothian cyst and cervical choriocarcinoma. The risks of cervical pregnancy are mainly severe hemorrhage, necessitating hysterectomy in many situations, and it usually occurs in nulliparous or low-parity women, adding to the dilemma of management.