What is the cause of failed pregnancy?

A blighted ovum occurs when a fertilized egg implants in the uterus but doesn't develop into an embryo. It is also referred to as an anembryonic (no embryo) pregnancy and is a leading cause of early pregnancy failure or miscarriage. Often it occurs so early that you don't even know you are pregnant.

How likely is it for a pregnancy to fail?

The estimated figure is that miscarriage happens in around 1 in 4 recognised pregnancies, with 85% of those happening in the first trimester (weeks 1 to 12). A 'late' miscarriage, which is much less common, may occur between weeks 13 to 24 of pregnancy.