Complete Molar Pregnancy

By usmlevideoss

Introduction: Molar pregnancy is part of a spectrum of gestational trophoblastic tumors that include benign hydatidiform moles, locally invasive moles, and choriocarcinoma. 

Hydatidiform mole is the most common form of gestational trophoblastic disease and is benign in nature. Two distinct forms of hydatidiform mole exist: complete and partial moles.

Complete molar pregnancy is characterized by abnormal proliferation of trophoblastic tissue, leading to the formation of a non-viable pregnancy. It results from abnormal fertilization where no fetal tissue develops.

Incidence: Occurs in 1 in 1500 pregnancies.

Pathophysiology: It occurs when an empty egg (with no maternal DNA) is fertilized by one or two sperm. Approximately 90% of cases are due to an empty egg fertilized by one sperm (with subsequent duplication of DNA); 10% of cases are due to an empty egg fertilized by two sperm.

Karyotype: Diploid (46,XX or 46,XY)

  • 46XX (most common): Duplication of a single sperm’s DNA.
  • 46XY: Fertilization by two sperm.
  • Since the egg lacks maternal DNA, the genetic material is entirely paternal, leading to abnormal trophoblastic growth and absence of an embryo.

Clinical Manifestations 

1.Symptoms:

  • Abnormal vaginal bleeding: Often painless and the most common presenting symptom.
  • Exaggerated pregnancy symptoms: Severe nausea and vomiting (hyperemesis gravidarum) due to elevated hCG levels.
  • Absence of fetal movements or heartbeat.

2.Signs:

  • Enlarged uterus: Uterine size greater than expected for gestational age.
  • Theca-lutein cysts: Bilateral ovarian cysts due to overstimulation by hCG.
  • Pre-eclampsia: Rarely, may develop in the first trimester (unusual for normal pregnancies).

Diagnosis

1.hCG Levels: The principal characteristic of gestational trophoblastic neoplasms is their capacity to produce hCG. Markedly elevated beta-hCG levels, often much higher than expected for gestational age.

2.Ultrasound Findings: “Snowstorm” or “cluster of grapes” appearance due to multiple cystic spaces in the placenta; Absence of fetal tissue or amniotic sac.

3.Histopathology: Gross: Markedly hydropic villi, which resemble cluster of grapes. No fetal parts. Microscopic: All villi are edematous and have prominent trophoblast proliferation 

4.Immunohistochemical staining for p57 expression: p57KIP2 is a nuclear protein whose gene is paternally imprinted and maternally expressed. This means that the gene product is produced only in tissues containing a maternal allele. Because complete moles contain only paternal genes, the p57KIP2 protein is absent in complete moles, and tissues do not pick up this stain. 

Complications

1.Persistent Gestational Trophoblastic Disease (GTD): Occurs in 15–20% of cases, requiring further treatment.

2.Choriocarcinoma: Rare but serious malignant transformation of trophoblastic tissue.

3.Hyperthyroidism: Elevated hCG mimics TSH, causing thyrotoxicosis in some cases.

4.Acute respiratory distress may occur due to embolization of trophoblastic tissue into the pulmonary vasculature, thyrotoxicosis, or simple fluid overload.

4.Preeclampsia: Signs of preeclampsia (hypertension, headache, proteinuria, and edema) in the 1st trimester or early 2nd trimester. 

Management

1.Evacuation of Uterus:

  • Suction curettage: Preferred method to remove molar tissue.
  • Hysterectomy may be considered for women who do not desire future pregnancies.

2.Monitoring:

  • hCG follow-up: Serial hCG levels until they normalize to detect persistent disease.
  • Regular hCG monitoring for 6–12 months to ensure remission.
  • A chest radiograph can rule out metastasis to the lungs

3.Contraception: Strongly recommended during hCG monitoring to avoid confusion with new pregnancy.

4.Chemotherapy: Reserved for persistent GTD or malignant transformation (e.g., methotrexate or actinomycin-D).

Prognosis: With proper treatment and follow-up, the prognosis is excellent, with cure rates approaching 100%. Approximately 20% of women will have recurrence in subsequent pregnancies. Most women can achieve a normal pregnancy after resolution of a molar pregnancy.

Summary: A complete molar pregnancy is a non-viable pregnancy with no fetal tissue. Elevated hCG and the “snowstorm” ultrasound pattern are hallmark diagnostic features. Management includes suction curettage and hCG follow-up to monitor for complications like persistent GTD or choriocarcinoma. Emphasize contraception during follow-up to prevent confusion with rising hCG from a new pregnancy.

SUPERFormula 

Patient presents with abnormal bleeding, enlarged uterus, and hyperemesis + Abnormally elevated hCG levels + “Snowstorm” or “Cluster of grapes” appearance on ultrasound + no fetal parts +  46,XX or 46,XY karyotype + Managed by suction curettage, hCG monitoring, and possible chemotherapy = Complete molar pregnancy 

 

SUPERPoint: Complete molar pregnancy is a non-viable pregnancy caused by abnormal fertilization, characterized by trophoblastic overgrowth, elevated hCG, and a “snowstorm” ultrasound appearance, requiring uterine evacuation and close hCG monitoring to prevent complications like persistent GTD or choriocarcinoma.

References: 

-10-17: Molar Pregnancy (Hydatidiform Mole) Suzanne Dooley-Hash; Kevin J. Knoop; The Atlas of Emergency Medicine 

-Williams Obstetrics, 26e

  1. Gary Cunningham, Kenneth J. Leveno, Jodi S. Dashe, Barbara L. Hoffman, Catherine Y. Spong, Brian M. Casey

-CURRENT Diagnosis & Treatment: Obstetrics & Gynecology, 12e

Alan H. DeCherney, Lauren Nathan, Neri Laufer, Ashley S. Roman

-Pathology: The Big Picture

Walter L. Kemp, Dennis K. Burns, Travis G. Brown