Usually human chorionic gonadotrophin (hCG) or a GnRH agonist, given at a precise time — commonly around 34 to 36 hours before egg collection. hCG can remain in the body for several days and cause a false positive on an early pregnancy test.
Fertility Glossary
Trigger injection
An injection that matures the eggs and sets the timing for collection or insemination.
Related terms
Egg collection
Removing eggs from the ovaries with a needle guided by ultrasound.
hCG
Human chorionic gonadotrophin — the hormone measured by pregnancy tests.
GnRH agonist
A medicine that first stimulates and then suppresses the body's own hormones.
Ovarian hyperstimulation syndrome (OHSS)
An over-response to fertility medication causing swollen, painful ovaries.