What happens during  in vitro fertilization may differ slightly from clinic, but a typical  treatment follows the main steps described on this article.

FOR WOMEN

STEP 6: Embryo transfer

A few days after the eggs are collected, the embryos are transferred into your womb. This is done using a thin tube called a catheter that’s passed into your vagina. This procedure is simpler than egg collection and similar to having a cervical screening test. The number of embryos that will be transferred should be discussed before treatment starts. It usually depends on your age :

• Women under 37 years in their 1st in vitro fertilization should only have a single embryo transfer. In their 2nd in vitro fertilization, they should have a single embryo transfer if 1 or more top-quality embryos are available. Doctors should only consider using 2 embryos if no top-quality embryos are available. In the 3rd in vitro fertilization cycle, no more  than 2 embryos should be transferred.
• Women aged 37 to 39 years in their 1st and 2nd full in vitro fertilization cycles should also have a single embryo transferred if there are 1 or more top-quality embryos. Double embryo transfer should only be considered if there are no top-quality.
• Women aged 40 to 42 years may have a double embryo transfer..

If any suitable embryos are left over, they may be frozen for future in vitro fertilization attempts.