A molar pregnancy is an abnormality of the placenta, caused by a problem when the egg and sperm join together at fertilization. Molar pregnancies are rare, occurring in 1 out of every 1,000 pregnancies. Molar pregnancies are also called gestational trophoblastic disease (GTD), hydatidiform mole or simply referred to as a "mole."
A molar pregnancy is the result of a genetic error during the fertilization process that leads to growth of abnormal tissue within the uterus. Molar pregnancies rarely involve a developing embryo, and the growth of this material is rapid compared to normal fetal growth. It has the appearance of a large and random collection of grape-like cell clusters. There are two types of molar pregnancies, "complete," and "partial."
Complete molar pregnancies have only placental parts (there is no baby), and form when the sperm fertilizes an empty egg. Because the egg is empty, no baby is formed. The placenta grows and produces the pregnancy hormone, hCG. Unfortunately, an ultrasound will show that there is no fetus, only a placenta.
Partial Mole occurs when the mass contains both the abnormal cells and an embryo that has severe defects. In this case the fetus will be overcome by the growing abnormal mass rather quickly. An extremely rare version of a partial mole is when twins are conceived but one embryo begins to develop normally while the other is a mole. In these cases, the healthy embryo will very quickly be consumed by the abnormal growth.
Although the removal of a molar pregnancy is not the termination of a developing child, it is still a loss. Even when an embryo is present, it does not have the opportunity to develop into a child. Most women discover that they are dealing with a molar pregnancy after the discovery and anticipation of being pregnant. Dreams, plans and hopes are cancelled all at once; it is still a significant loss.