Molar Pregnancy (Hydatidiform Mole)

Molar pregnancy is an abnormal form of pregnancy in which a non-viable fertilized egg implants in the uterus and will fail to come to term (will not develop into a child). Instead, the cells divide and replicate into a growing mass (mole) of non-foetal tissue.

Molar pregnancy is a gestational trophoblastic disease in which a non-viable egg grows into a mass (tumour) in the uterus that has swollen chorionic villi.

• Can develop when a fertilized egg does not contain an original maternal nucleus.
• Usually contains no foetal tissue.
• Characterized by the presence of a hydatidiform mole (or hydatid mole).
• Approximately 20% of women with a complete mole develop a trophoblastic malignancy (malignant disease // cancer)

Complete hydatidiform moles have a 2–4% risk of developing into choriocarcinoma in Western countries and 10–15% in Eastern countries, and have a 15% risk of becoming an invasive mole.

Molar pregnancies make up 1 in 1,000 pregnancies in the US and up to 1 in 100 pregnancies in parts of Asia.

Symptoms

• Vaginal bleeding- molar tissue separates from the decidua, causing bleeding.
• Uterus may become distended by large amounts of blood, and dark fluid may leak into the vagina.
• Hyperemesis - severe nausea and vomiting due to very high levels of human chorionic gonadotropin (hCG).
• Hyperthyroidism - thyroid gland is stimulated by the high levels of circulating hCG or by a thyroid stimulating substance (ie, thyrotropin) produced by the trophoblasts.

Partial mole

Partial moles do not generate the same clinical features as a complete mole. Patients instead present with signs and symptoms consistent with an incomplete or missed abortion, including vaginal bleeding and absence of foetal heartbeat.