Q. What is a “chemical pregnancy?”
A. A chemical pregnancy—also called a biochemical pregnancy—is one that’s diagnosed by a pregnancy hormone test. In a chemical pregnancy, the egg is fertilized, the fertilized egg implants in the uterine cavity and starts to grow, and the placenta produces the pregnancy hormone that’s measured by most pregnancy tests. So by definition there is a pregnancy.
But the pregnancy never progresses to the point where it can be confirmed with a clinical test (such as an ultrasound, or physical palpation of an enlarging uterus during a medical examination). Chemical pregnancies are more common than one would think, but they’re such short-lived pregnancies that they often go undiagnosed. A woman might have a period that’s only late by a few days and never realize she’d been pregnant. These days, chemical pregnancies are often determined in women undergoing fertility treatment, because pregnancy tests with IVF (in vitro fertilization) procedures are often performed very early, before a period would be missed.