From the Guidelines
A molar pregnancy forms when there is an abnormal fertilization of an egg, resulting in abnormal growth of placental tissue, with two types: complete and partial molar pregnancies, as described in the 2019 NCCN clinical practice guidelines in oncology 1.
Molar Pregnancy Formation
The formation of a molar pregnancy is characterized by abnormal fertilization, which can occur in two ways:
- Complete molar pregnancy, where an empty egg is fertilized by one or two sperm, resulting in tissue with only paternal chromosomes, as noted in the study published in the Journal of the National Comprehensive Cancer Network 1.
- Partial molar pregnancy, where a normal egg is fertilized by two sperm, resulting in tissue with 69 chromosomes instead of the normal 46, also discussed in the same study 1. This abnormal genetic makeup causes the placental tissue to develop into a mass of cyst-like vesicles rather than a normal placenta, and no viable fetus develops.
Risk Factors and Treatment
Risk factors for molar pregnancy include maternal age (under 20 or over 35), previous molar pregnancy, and certain ethnic backgrounds. Treatment typically involves surgical removal of the abnormal tissue through dilation and curettage (D&C), followed by monitoring of hCG levels to ensure complete removal and to detect any potential progression to gestational trophoblastic neoplasia, as recommended in the ESMO clinical practice guidelines for diagnosis, treatment, and follow-up 1. Patients should avoid pregnancy during the monitoring period, which can last 6-12 months depending on how quickly hCG levels normalize.
Monitoring and Follow-up
Monitoring of hCG levels is crucial to detect any potential progression to gestational trophoblastic neoplasia, with guidelines suggesting that hCG levels should be monitored every 2 weeks until the patient has 3 consecutive normal assays, with monthly hCG monitoring for an additional 6 months, as outlined in the 2019 NCCN clinical practice guidelines in oncology 1. The safest method of evacuation is suction dilation and curettage (D&C) under ultrasound control to ensure adequate emptying of uterine contents and to avoid uterine perforation, as recommended in the study published in the Annals of Oncology 1.
From the Research
Formation of Molar Pregnancy
- Molar pregnancy, also known as hydatidiform mole, is a disorder of pregnancy that arises from abnormal fertilization with marked proliferation of syncytiotrophoblasts 2.
- It is the most common disorder in a category of pathologies known as Gestational Trophoblastic Diseases that are associated with abnormal fertilization in pregnancy 3.
- Complete and partial molar pregnancies can occur, with complete moles having a higher risk of progression to gestational trophoblastic neoplasia (GTN) 2.
Abnormal Fertilization
- Abnormal fertilization is the primary cause of molar pregnancy, leading to the proliferation of syncytiotrophoblasts 2.
- This abnormal fertilization can result in the formation of a molar pregnancy, which can be either complete or partial 2.
Incidence and Diagnosis
- Hydatidiform mole complicates approximately 1 in 2000 pregnancies in the United States 4.
- Earlier diagnosis has reduced the frequency of severe medical complications at presentation, but the risk of progression to GTN has remained unchanged 2.
- Diagnosis can be made prior to evacuation if the signs and symptoms are kept in mind, and a thorough physical examination and laboratory testing are necessary after a diagnosis is established 4, 3.