Introduction to the 1st, 2nd and 3rd generation of IVF

1st generation IVF –

Refers to conventional IVF (the retrieved eggs are incubated with processed sperm to allow natural fertilization to take place).

It is mainly used for treating infertility caused by female ovulation or tubal factors.

2nd generation IVF –

Refers to utilization of intracytoplasmic sperm injection (ICSI) to promote fertilization (where fertilization is facilitated by selecting a good looking sperm to inject into a mature egg under the microscope).

It applies to:

• Male infertility – with 3 semen analysis confirming low sperm count, poor motility and/or morphology.
• Failed fertilization or with very low fertilization rate during previous IVF treatment.
• To fertilize eggs after cryopreservation or in vitro maturation (IVM)
• For patients undergoing preimplantation genetic testing (PGT)
• For patients with repeated IVF failures

3rd generation IVF –

Refers to Preimplantation Genetic Testing (PGT) to select embryos with normal chromosome numbers and structures (PGT-A), or to exclude embryos with known inherited single gene disorder (PGT-M/-SR) before transferring back to the uterus, as an attempt to improve the implantation and pregnancy rate.

It applies to:

• Women of advanced age (age ≥35)
• History of recurrent abortions (≥3 consecutive spontaneous abortions)
• Repeated implantation failures (≥3 times)
• Previous birth of a child with chromosomal abnormalities
• Couples known to be carriers of chromosomal abnormalities
• Severe male factor infertility

So first, second and third generation IVF are for different indications in infertile couples and not that the third generation is better than the second generation or the second generation is better than the first generation. It has also to be noted that not all embryos can develop to the blastocyst stage required for PGT.