What is a molar pregnancy? What is a chemical pregnancy?
A molar pregnancy happens when there are certain abnormalities in the fertilized egg at conception. The fertilized egg either never develops into an embryo (this is called a complete mole) or it develops abnormally and can’t survive (this is a partial mole). In normal pregnancies, the fertilized egg contains 23 chromosomes from the father and 23 from the mother. In most complete molar pregnancies, the fertilized egg contributes no maternal chromosomes and the chromosomes from the father’s sperm are duplicated, so you end up with two copies of chromosomes from the father and none from the mother. In this case, there’s no embryo, amniotic sac, or any normal placental tissue. Instead, the placenta forms a mass of cysts that looks like a cluster of grapes. In most partial molar pregnancies, the fertilized egg has the normal complement of chromosomes from the mother but double the chromosomes from the father, so there are 69 chromosomes instead of the normal 46. (That can happen when chromo
