Such pregnancies are relatively rare, occurring in one out of 1,500 women. But once discovered, a molar pregnancy needs to be treated immediately by removing all of the molar tissue. Otherwise, serious health problems can occur.
Molar pregnancies can be traced to genetics. Somehow, the genetic information contained in a sperm or egg is damaged. Normal human cells contain 23 pairs of chromosomes. In a normal pregnancy, one chromosome in each pair comes from the father and one comes from the mother. However, in a molar pregnancy, all of the fertilized egg chromosomes come from the father. For reasons that are not clear, the chromosomes from the mother’s egg are lost or inactive, while the father’s chromosomes duplicate. The egg may not have a nucleus or may have an inactive nucleus.
In a partial molar pregnancy, a mother’s chromosomes remain, but the father provides two sets of chromosomes. Thus, the embryo has 60 chromosomes instead of 46. This happens when two sperm fertilize a single egg or when the father’s chromosomes are duplicated.
Two Forms of Molar Pregnancy
There are two types of molar pregnancy: