What are the diagnostic criteria for a complete or partial hydatidiform (gestational trophoblastic disease) mole pregnancy?

From the Guidelines

Diagnosing a molar pregnancy requires a combination of clinical assessment, laboratory tests, and imaging studies, with the most reliable approach beginning with a quantitative serum hCG test and transvaginal ultrasound, followed by histopathological examination of tissue obtained through suction curettage. The diagnosis of molar pregnancy is often suspected based on ultrasound findings, which may show a characteristic "snowstorm" or "cluster of grapes" appearance in complete molar pregnancies, with multiple vesicles and absence of a fetus 1. In partial molar pregnancies, ultrasound may show an abnormal placenta with cystic spaces and possibly fetal parts. Clinical symptoms that raise suspicion include vaginal bleeding, severe nausea and vomiting, early preeclampsia before 20 weeks, and uterine size larger than expected for gestational age.

Key Diagnostic Steps

• Quantitative serum hCG test to detect abnormally high levels compared to normal pregnancies
• Transvaginal ultrasound to reveal characteristic ultrasound findings
• Histopathological examination of tissue obtained through suction curettage for definitive diagnosis
• Serial hCG monitoring after evacuation to detect persistent trophoblastic disease Some key points to consider in the diagnosis of molar pregnancy include:
• The importance of histological examination of every termination, as unsuspected molar pregnancies can occur 1
• The need for careful hCG monitoring to look for the recurrence of disease, suggesting malignant change indicated by a plateaued or rising hCG on three and two consecutive samples, respectively
• The risks associated with re-biopsy to confirm malignant change, including the risk of triggering life-threatening haemorrhage 1

Laboratory and Imaging Findings

• Elevated hCG levels, often greater than 100,000 IU/L in complete molar pregnancies
• Anemia, hyperthyroidism, and other laboratory abnormalities
• Characteristic ultrasound findings, including a heterogenous mass and cystic spaces
• Chest X-ray and other imaging studies to rule out metastatic disease The NCCN Panel recommends a workup of patients with suspected molar pregnancy to include history and physical, pelvic ultrasound, quantitative hCG assay, complete blood count with platelets, liver, renal, and thyroid function tests, and blood type and screen 1.

From the Research

Diagnosing Molar Pregnancy

• Molar pregnancy is a rare complication of pregnancy, usually confirmed with a markedly elevated beta-hCG and a "snowstorm" appearance on pelvic ultrasound 2.
• Patients frequently present with a positive pregnancy test, vaginal bleeding, nausea, and vomiting 2.
• Qualitative beta-hCG urine assays may be misleading in the presence of molar pregnancy, and quantitative serum hCG should be used instead 2.
• Hysteroscopy can be a useful tool for diagnostic protocol in case of early atypical molar pregnancy, providing conclusive diagnostic images of hydropic degeneration of the chorionic villi 3.
• Following serial quantitative beta-human chorionic gonadotropin (B-hCG) levels after spontaneous, therapeutic, and elective abortions can help detect potentially life-threatening molar and ectopic pregnancies 4.
• Point-of-care ultrasound (POCUS) can be used to diagnose molar pregnancy in the emergency department, showing a heterogeneous mass with several anechoic areas 5.
• Early ultrasound diagnosis and follow-up of molar pregnancies can identify placental molar changes and establish the differential diagnosis in utero of the various forms of placental molar transformations 6.
• Ultrasound examination can correctly identify molar changes in early pregnancy, and together with hCG level and uterine Doppler measurements, can establish the differential diagnosis 6.