Molar pregnancy or gestational trophoblastic disease (GTD) is diagnosed when abnormal cells called trophoblasts develop in the placenta. There are two types of molar pregnancies. In a complete molar pregnancy, there is no fetus, only a mass of abnormal cells in the uterus. In a partial molar pregnancy, a fetus does develop, but because of the abnormal cells, it is not viable. About one in every 1,000 to 1,500 pregnancies is a molar pregnancy.
A molar pregnancy may mimic that of a healthy pregnancy in the symptoms a woman experiences. She may experience nausea, bloating, and vaginal bleeding with a molar pregnancy— which aren’t unusual symptoms in a healthy pregnancy. A molar pregnancy is usually spotted in a routine ultrasound scan between weeks 8-14. Alternatively, if a woman has had a miscarriage, it may be evidence that she had a molar pregnancy in tests and scans following the miscarriage. Other signs and symptoms may include:
A molar pregnancy occurs when there is a problem with the way the egg was fertilized. The two types of molar pregnancies are:
Complete molar pregnancy: When an “empty egg”—or an egg with no genetic information—is fertilized by one or two sperm, and all of the genetic code is from the father. No fetus will develop in this case. Instead, it will begin to form abnormal tissue that looks like a cluster of grapes and can fill the uterus.
Partial Molar Pregnancy: When an egg is fertilized by two sperm, giving it 69 chromosomes instead of 46. In this case, a fetus may begin to form, but with severe defects.
After the molar tissue is removed from the uterus, it is possible that some tissue may remain and grow. This happens in 15-20 percent of complete molar pregnancies, and in five percent of partial molar pregnancies. When this happens, it is called persistent gestational trophoblastic neoplasia (GTN).
Persistent GTN may require some chemotherapy to rid the uterus of the molar tissue completely. Rarely, a patient will need to get a hysterectomy.
Molar pregnancy appears to be a normal pregnancy until an ultrasound detects it. In earlier weeks of pregnancy, the ultrasound may be done vaginally.
A molar pregnancy can be detected from around weeks eight or nine. The ultrasound of a complete molar pregnancy may be unusual because:
The ultrasound of a partial molar pregnancy may show:
A molar pregnancy is not a viable pregnancy, and it must be treated right away. The molar tissue must be removed from the uterus as soon as possible.
Removal of molar tissue happens with the following procedures:
After the molar tissue is removed, your doctor will monitor your HCG levels with blood tests to make sure no leftover tissue has begun to grow. You may be monitored for six months after a molar pregnancy. Your doctor may recommend that you wait six to 12 months before getting pregnant again. The chance of having another molar pregnancy after a woman has had one is about one percent. In most cases, a woman can go on to have healthy pregnancies after she has had a molar pregnancy.
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