Stimulation and ovarian hyperstimulation syndrome
Not eliminated. Three things reduce it, and each has a trade-off.
Ovarian hyperstimulation syndrome is the main serious complication of the drug phase of IVF. You will often be told it is now rare. It is less common than it was, and "rare" overstates it.
In recent large randomized trials of fresh transfer, hyperstimulation ran at 2.0% in ovulatory women without polycystic ovary syndrome and 7.1% in women with PCOS. A prospective series of 1,058 retrievals recorded severe hyperstimulation in 2.7%.
Three changes reduce it, and each buys something at a price:
| Change | Effect on hyperstimulation | What it costs |
|---|---|---|
| Antagonist rather than long agonist protocol | Roughly 11% falls to 6% to 9% | No loss of live birth. More cycles cancelled for poor response. |
| GnRH agonist trigger instead of hCG | Roughly 5% falls to between nil and 2% | In a fresh transfer, live birth roughly halves in that cycle |
| Freezing all embryos rather than a fresh transfer | Roughly 3% falls to 1% | No loss of cumulative live birth, but higher blood pressure risk in pregnancy |
for a woman with a 31% chance of live birth with HCG, the chance with a GnRH agonist would be between 12% and 24%.
That penalty does not apply if the plan is to freeze everything and transfer later, and it did not appear in donor-recipient cycles. So the agonist trigger is a good choice combined with a freeze-all plan and a poor one combined with a fresh transfer. If it is offered to you, ask which plan it is part of.
The extreme end of what protocol choice can do: in 4,052 donor cycles, every one of the 22 cases of moderate or severe hyperstimulation occurred in an hCG-triggered cycle. There were none among the 1,519 agonist-triggered antagonist cycles.