(CNN) -- It's a technology that's helped millions of couples have children.
Now in-vitro fertilization, or IVF, has reached a major milestone.
Fertility experts say five million children have been born thanks to medical reproductive assistance.
The announcement came earlier this week at an international convention of fertility doctors and researchers.
The first so-called "test tube baby" was born in 1978.
IVF is a procedure where a woman's eggs are fertilized outside her body -- in a laboratory -- and reinserted into the birth mother's uterus.
It's not cheap -- the National Institutes of Health estimates IVF can cost between $12,000-17,000.