What Is a Molar Pregnancy?

A molar pregnancy is a rare pregnancy complication that results from the abnormal fertilization of an egg. It is sometimes referred to as a hydatidiform mole or gestational trophoblastic disease (GTD) and is estimated to occur in less than 1% of pregnancies or 1 out of every 1,000 pregnancies. Molar pregnancies may be complete or partial, but placenta abnormalities occur in both types.

When a complete molar pregnancy occurs, abnormal placental tissue grows and contains tumors or cysts. An embryo is not present in a complete molar pregnancy. However, abnormal placental tissue produces a hormone called hCG, which normal placental tissue also produces during pregnancy. This hormone ultimately causes the symptoms associated with pregnancy and can result in a positive pregnancy test even though the person is not pregnant. 

If abnormal placental tissue grows with an embryo and the egg has been fertilized by two sperm, it is considered a partial molar pregnancy. An embryo in a partial molar pregnancy has a chromosomal abnormality since it contains both the mother’s chromosomes and two sets of chromosomes from the father, resulting in 69 chromosomes rather than 46. Although the embryo may continue to develop, it typically does not survive.

While molar pregnancies are rare, it is important to understand that anyone can experience one. Some individuals are at higher risk of having a molar pregnancy, such as those who have had two or more miscarriages or those with a previous history of molar pregnancies. Molar pregnancies are characterized by several symptoms, including: 

• Nausea and vomiting 
• Vaginal bleeding during the first three months of pregnancy 
• High HCG levels 
• Anemia 
• Abdominal swelling 
• High blood pressure (preeclampsia) 
• Small grape-like cysts discharged from the vagina 

Most individuals who have molar pregnancies experience full recovery and can have viable pregnancies in the future with appropriate treatment. Although molar pregnancies cannot result in a live birth, they can pose a serious health risk due to complications if they are untreated. Early diagnosis and treatment are necessary, and even after treatment, hCG levels must be monitored to prevent further issues. Taking this into consideration, those who suspect they may be experiencing a molar pregnancy are encouraged to contact a healthcare provider and seek immediate medical attention.

Sources

“Molar pregnancy.” Cleveland Clinic. https://my.clevelandclinic.org/health/diseases/17889-molar-pregnancy 

“Molar pregnancy.” Mayo Clinic. https://www.mayoclinic.org/diseases-conditions/molar-pregnancy/symptoms-causes/syc-20375175 

“Molar pregnancy: Symptoms, risks, and treatment.” American Pregnancy Association. https://americanpregnancy.org/healthy-pregnancy/birth-defects/molar-pregnancy/