Complications associated with assisted reproduction can be life-threatening to a pregnant woman. A radiologist’s awareness and prompt recognition of these can help safeguard the health of a mother and her fetus. The February issue of Emergency Radiology provides a succinct review that describes imaging findings related to ovarian hyper stimulation syndrome (OHSS), to non-gynecological systemic complications caused by an altered blood coagulation profile, and to other pregnancy and post-delivery complications.
OHSS affects women undergoing in vitro fertilization, ovulation induction, or intrauterine insemination who are taking medications to stimulate the development of eggs in the ovaries. A very small percentage of women develop OHSS, which occurs when ovarian blood vessels react abnormally to a high level of human chorionic gonadotropin (hCG). Severe OHSS can cause fluid collection in the abdomen and/or chest, thromboembolism, arterial hypotension, ovarian torsion or rupture, kidney failure, and/or electrolyte imbalances.
Early OHSS occurs 3-7 days after hCG administration whereas more serious, late OHSS occurs due to endogenous hCG from pregnancy, 12-17 days after ovarian trigger. Findings identified on ultrasound are significantly enlarged ovaries seen with multiple large follicles/corpus luteal cysts that have the appearance of a wheel/spoke pattern. Ascites and pleural effusion is often seen, but can be clear or hemorrhagic. Anu Rao, MD, assistant professor of radiology at the Kidwai Memorial Institute of Oncology in Bangalore, India, recommends that because massive ascites can exist without significant ovarian enlargement, it is very important for radiologists to perform an overall assessment of OHSS for appropriate clinical management. Patients should have follow-up imaging until symptoms of the syndrome resolve.
Ovarian torsion may be identified by unilateral asymmetric enlargement of the affected ovary on ultrasound if associated with ovarian stromal heterogeneity caused by hemorrhage and edema. Another imaging feature is peripheral displacement of follicles as is absence or abnormality of color Doppler flow. Such findings merit a magnetic resonance (MR) with contrast scan using T1, T2, and fat suppression sequences.
Pregnant women who have had in vitro fertilization are 25% to almost 50% more likely to experience pulmonary embolism and venous thromboembolism. Radiologists need to be aware of this vulnerability of these patients.
The incidence of ectopic pregnancy is much higher in women who have had assisted pregnancies than those who have not, with tubal factor infertility increasing the incidence of ectopic pregnancy to as high as 11%, according to Dr. Rao. When a yolk sac or embryo can be visualized or a tubal ring sign seen, ultrasound is 99%-100% specific in identifying ectopic pregnancy. However, ultrasound imaging may not identify as many as one-third of ectopic pregnancies. MR imaging (MRI) may show common signs of ectopic gestation, including the presence of hematosalpinx, heterogeneous mass with hemorrhagic components, bloody ascites, tubal dilation, and wall enhancement.
Interstitial pregnancy is estimated to occur in 1 out of every 3,600 assisted pregnancies. This condition is characterized on ultrasound as an eccentrically located gestation sac surrounded by a thin layer (less than 5 mm) of myometrium. Cornual pregnancies very rarely occur, but can be identified as a “claw sign” on ultrasound. This is visualized when uterine parenchyma forms sharp angles around the ectopic gestational sac.
Cervical pregnancy is rare, but occurs 10 times more in assisted pregnancies. The typical imaging finding is an hourglass- or figure eight-shaped uterus. An MRI can show a mixed signal intensity lobulated mass with a partial or complete dark rim on T2-weighted images.
Abdominal pregnancies, which can be asymptomatic until an advanced gestational age, occurs in less than 2% of all ectopic pregnancies. MRI is recommended, and will tend to show an empty uterus, lack of myometrium surrounding the sack, and placental localization. If a calcified fetal mass is seen on imaging, a computed tomography scan (CT) may be able to better identify the fetal structure.
The occurrence of simultaneous intra- and extrauterine pregnancy is exceedingly rare, with an incidence of about 1 in 30,000 pregnancies. However, it is more common in women who have had infertility treatment. Dr. Rao recommends that when an intrauterine pregnancy is identified, radiologists should carefully evaluate the adnexa for a second pregnancy, which may have the appearance of a corpus luteal cyst.
Dr. Rao told Applied Radiology that he wrote this review with the hope that radiologists would benefit from a summary of the conditions they might encounter with women presenting with symptoms of pregnancy-related complications. “Radiologists and in vitro fertilization specialists play a very important role to promptly identify acute complications and initiate further investigations or treatments appropriately,” Dr. Rao said. “Radiologists are bound to encounter both common and uncommon complications with these patients during their clinical career. Enhanced awareness can make a huge advantage in the prompt and accurate diagnosis of these conditions.”
Clinical implications of imaging findings following assisted reproduction. Appl Radiol.