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11/5/2023

Diagnosis and Management of Molar Gestation

Molar gestation arises from villous trophoblasts in the setting of aberrant fertilization. Moles are at the benign end of the spectrum of gestational trophoblastic disease (GTD), which includes malignant tumors (invasive mole, choriocarcinoma, placental-site trophoblastic tumor, and epithelioid trophoblastic tumor), commonly referred to as gestational trophoblastic neoplasia (GTN).

Molar gestation comprises 2 distinct subtypes: complete moles and partial moles. Complete moles are diploid, usually paternally derived, and have no fetal tissue. Partial moles are triploid, bipaternal, and usually involve fetal tissue. Unregulated trophoblastic proliferation causes elevated concentrations of human chorionic gonadotropin (hCG), commonly exceeding 100,000 IU/L in complete moles. While the initial management is the same for both subtypes, distinguishing between the entities is critical because the risk of medical complications and development of postmolar GTN is significantly higher for complete moles (20% vs 4%).

Historically, moles presented later in pregnancy with excessive uterine size, anemia, preeclampsia, hyperemesis, hyperthyroidism, and respiratory failure. However, with the increased use of ultrasonography in early pregnancy, most moles are diagnosed incidentally in the first trimester due to bleeding and/or elevated hCG. Ultrasound findings of a multicystic mass filling the uterus and theca lutein cysts are classic for complete moles, A placenta with focal cystic changes and a nonviable fetus are suggestive of a partial mole. However, in early pregnancy, these ultrasound findings can be absent or subtle.

Suspected molar gestation should be managed surgically and expeditiously. In patients who desire uterine preservation, suction dilation and evacuation is preferred. These patients are at increased risk of hemorrhage, and uterotonics and blood products should be available. Ultrasound guidance can be considered and might improve the rate of complete evacuation. RhD immunoglobulin should be administered as indicated. Medical evacuation is discouraged because of high rates of failure and hemorrhage and increased risk of postmolar GTN. Hysterectomy is an appropriate alternative in patients who do not desire uterine preservation or who have risk factors for GTN, and this approach can reduce the risk of postmolar GTN by 80%. Uterine contents should be sent for histopathologic examination.

After a molar pregnancy, there is a 1% to 2% risk of a second occurrence and a 15% to 20% risk of a third. More than half of patients with consecutive molar gestations have familial recurrent hydatidiform mole syndrome, and genetic testing is recommended. Twin pregnancy with a mole and a viable pregnancy is rare, but it can be managed expectantly and up to 60% result in live birth.

The risk of postmolar GTN is greatest in the first year, and patients should undergo surveillance with serial hCG measurement using an assay that can detect all forms of this hormone. Several different organizations have guidelines for the duration and timing of surveillance testing. The Society of Gynecologic Oncology recommends checking hCG levels weekly until normalization, and then monthly for 3 months after complete moles and 1 month after partial moles. This recommendation has been endorsed by the American College of Obstetricians and Gynecologists. Reliable contraception and delaying pregnancy until after surveillance are highly recommended.

Risk factors for GTN include an hCG concentration at diagnosis greater than 100,000 IU/L, excessive uterine size, theca lutein cysts, and age older than 40 years. Despite earlier diagnosis of molar gestation, the incidence of postmolar GTN has remained constant.

There are no differences in fertility, live birth rates, or other pregnancy outcomes for patients with a history of GTD. These patients should have first-trimester ultrasonography in subsequent pregnancies, and hCG should be measured 6 to 8 weeks after any pregnancy. Placental evaluation can be considered but is not mandatory in subsequent pregnancies.

Further Reading:

Horowitz NS, Eskander RN, Adelman MR, Burke W. Epidemiology, diagnosis, and treatment of gestational trophoblastic disease: A Society of Gynecologic Oncology evidenced-based review and recommendation. Gynecol Oncol. 2021 Dec;163(3):605-613. doi: 10.1016/j.ygyno.2021.10.003. Epub 2021 Oct 20. PMID: 34686354.

Soper JT. Gestational Trophoblastic Disease: Current Evaluation and Management. Obstet Gynecol. 2021 Feb 1;137(2):355-370. doi: 10.1097/AOG.0000000000004240. Erratum in: Obstet Gynecol. 2022 Jan 1;139(1):149. PMID: 33416290; PMCID: PMC7813445.

 

Final editing of initial publication performed by The Medical Pen, LLC.

Initial publication November 2023

 

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