A molar pregnancy, also known as gestational trophoblastic disease (GTD) or Hydatidiform mole, is the abnormal growth of tissue in the uterus. A molar pregnancy occurs due to an error in the fertilization process. The cells that would normally form into a placenta grow into a mass of uterine cysts that are typically benign, or non-cancerous. A molar pregnancy often appears to be a normal pregnancy in early stages. However, a molar pregnancy will not come to term and produce a fetus.
Types of Molar Pregnancy
During a normal pregnancy, a fertilized egg contains 46 chromosomes of DNA. These 46 chromosomes are composed of two sets of 23 chromosomes, one set from the mother and one set from the father. The mother’s chromosomes are contained in the egg. The father’s chromosomes are contained in the sperm. In a molar pregnancy, the fertilized egg does not contain two equal pairs of chromosomes. There are two main types: complete molar pregnancy and partial molar pregnancy.
In a complete molar pregnancy, all 46 chromosomes of the fertilized egg belong to the father. This typically occurs if the egg is “empty” or loses its DNA. The father’s sperm is duplicated due to the absence of the mother’s chromosomes. As a result, there is no embryonic development in a complete molar pregnancy. The resulting growth is abnormal placenta tissue.
In a partial molar pregnancy, 69 chromosomes are present because the father provides two sets of 23 instead of one set. In addition, the mother’s 23 chromosomes remain present, making a total of three sets. This error occurs because the father’s 23 chromosomes are either duplicated or two sperms fertilize the same egg. As a result, the growing embryo typically has severe defects. The fetus is quickly consumed by the abnormal tissue growth.
Symptoms of Molar Pregnancy
Indications of molar pregnancy may involve:
- Nausea and vomiting
- High blood pressure
- Overactive thyroid, or hyperthyroidism
- Absence of a fetal heartbeat
- Abnormally rapid uterine growth
- Abnormal vaginal spotting or bleeding
- Vaginal passing of grape-like cysts
Diagnosis and Treatment
A molar pregnancy often exhibits similar symptoms to a normal pregnancy. Therefore, close monitoring and testing is crucial to determine a molar pregnancy. On ultrasound, a molar pregnancy will typically appear as a cluster of grapes, also called a honeycombed uterus. A histopathological examination, or microscopic examination of the cells, is used to confirm the condition.
Immediately after a molar pregnancy is detected, it should be removed from the uterus. Methods for removal include surgical curettage and uterine suction. After the removal process, the patient should be closely monitored to ensure that there is no remaining tissue. Remaining tissue may continue to grow and reintroduce molar pregnancy complications.
Complications of Molar Pregnancy
A molar pregnancy can pose serious health risks if not properly diagnosed and treated.In 10% to 20% of cases, a molar pregnancy may become invasive. This condition is called persistent trophoblastic disease (PTD). During PTD, the hydatidiform mole may penetrate into the uterine wall and cause hemorrhaging and other complications.
In extreme cases, the hydatidiform mole may develop into choriocarcinoma. Choriocarcinoma is a rapidly-growing cancer that metastasizes, or spreads into other parts of the body. If an undiagnosed or untreated molar pregnancy develops into choriocarcinoma, the outlook is poor. The fatality rate of advanced, metastaticchoriocarcinoma is roughly 15% to 25%.