There are two types of hydatidiform mole, complete and partial. A hydatidiform mole miscarries by about 16 to 18 weeks gestational age. The other type of hydatidiform mole is called a partial mole and this is also a genetically abnormal pregnancy. In this case there are three sets of chromosomes instead of the usual two and this is called triploidy. Since with partial mole there are maternal chromosomes there is a fetus but because of the three sets of chromosomes this fetus is always grossly abnormal and will not survive.
Symptoms usually appear in the second or third month of pregnancy.
There may be abnormal bleeding or cramps or the passage of some tissue. There may be severe vomiting, more than in normal pregnancy. An ultrasound examination will make the diagnosis and will help distinguish mole from other early pregnancy abnormalities. You should report any new bleeding, any fever, or if you pass any tissue from your vagina. Although some studies have linked hydatidiform mole with dietary or genetic factors, and it has been found to have a higher incidence in the Far East, the real cause of hydatidiform mole is still unknown.