There is one number that every couple researches before walking into a fertility clinic: the success rate. It appears on websites, in brochures, and in consultation rooms, often in bold, often impressive, and almost always misunderstood.

The problem is not that clinics are lying. The problem is that "success" in IVF means very different things depending on who is measuring it and the gap between those definitions can mean the difference between going home with a baby and going home empty-handed.

Two Numbers, One Critical Difference

In fertility medicine, success is typically measured in one of two ways:

Clinical Pregnancy Rate (CPR): The percentage of IVF cycles in which a gestational sac with a fetal heartbeat is detected on ultrasound, usually around six to seven weeks. This is a confirmed pregnancy but not a guaranteed baby.

Live Birth Rate (LBR): The percentage of IVF cycles that result in the delivery of a living baby after 24 weeks of gestation. This is the number that actually matters to most couples.

The difference between these two figures is not trivial. For women under 35, the clinical pregnancy rate per cycle may sit around 55–60%, while the live birth rate for the same age group is closer to 40–45%, a gap of roughly 10–15 percentage points driven by early miscarriage, ectopic pregnancies, and fetal loss.

For women over 40, that gap widens........

© Forbes India