IVF Stimulation Protocols: Antagonist, Agonist and Dosing Explained

IVF stimulation protocols

Your protocol is the combination of which drugs suppress premature ovulation, which stimulate the ovaries, at what dose, and how the final egg maturation is triggered.

This page describes what the current ESHRE guideline recommends — and, just as usefully, what it recommends against.

Which protocol

The GnRH antagonist protocol is recommended over agonist protocols in the general IVF/ICSI population, on the grounds of comparable efficacy and higher safety. Strong recommendation.

It is also recommended specifically for predicted high responders, where OHSS risk is the concern.

Where a GnRH agonist is used, the long protocol is recommended over short or ultrashort versions.

A newer recommendation: the fixed antagonist protocol is probably preferred over the flexible one.

If a freeze-all is planned, progestin for pituitary suppression is probably equally recommended to GnRH analogues.

Dose

Conventional dosing is 150–225 IU. The guideline states there are limited indications to deviate from it.

That last row is worth pausing on, because escalating the dose is the intuitive response to low ovarian reserve and the evidence does not support it. Higher doses do not improve oocyte yield or live birth rates, while adding cost and side effects.

Mid-cycle dose adjustment is probably not recommended — in either direction. The guideline adds a good practice point that the starting dose therefore needs to suit the patient from the outset. In other words, the decision that matters is made before stimulation begins, not during it.

Which drug

Here the guideline finds broad equivalence, which is worth knowing if one brand is presented to you as superior:

• Recombinant FSH and hMG — equally recommended
• Follitropin delta and follitropin alfa or beta — equally recommended
• Long-acting and daily recombinant FSH — equally recommended in antagonist cycles for normal responders
• Recombinant FSH and purified or highly purified FSH — equally recommended in agonist protocols

On adding LH activity: r-hFSH with r-hLH and r-hFSH alone are probably equally recommended — for the general population, for low responders, and for women aged 35 and over. Three separate recommendations, all pointing the same way. So describing LH supplementation as necessary in older women is not supportable.

Combining r-hFSH with hMG is probably not recommended over either alone. Adding low-dose hCG to FSH stimulation is probably not recommended.

Monitoring

Ultrasound tracks follicle growth. Adding oestradiol to ultrasound monitoring is probably not recommended, and neither is routine monitoring of endometrial thickness during stimulation.

One measurement is probably recommended: serum progesterone on the day of trigger, in cycles planning a fresh transfer. Where it is raised, you should be counselled about potentially lower pregnancy rates — and any decision to defer transfer weighed alongside oocyte number, embryo number and embryo quality.

Trigger

Follicles are most often triggered at 16–22 mm.

Recombinant and urinary hCG are equally recommended. In agonist protocols, 5000 IU is probably preferred over 10,000 IU.

Where OHSS risk is high, a GnRH agonist trigger combined with freeze-all is recommended to minimise severe OHSS — a strong recommendation, and the single most effective preventive step. Dopamine agonists are also recommended to reduce early OHSS risk, particularly where hCG is used.

Recombinant LH is not recommended for triggering. A dual trigger — agonist plus hCG — is probably not recommended, in normal, low or high responders.

What the guideline recommends against

Almost every adjuvant reviewed received a recommendation against: growth hormone, DHEA, testosterone pre-treatment, myo-inositol, aspirin, sildenafil, adding letrozole or clomiphene to gonadotropins, and routine metformin with the antagonist protocol in PCOS.

If any of these is offered to you, it is reasonable to ask what evidence supports it in your specific situation.

Two terminology notes

The guideline replaced "poor responder" with "low responder", specifically to avoid implying anything about prognosis. It also asks clinicians to avoid non-standardised terms such as "healthy" responders or "kind" stimulation.

And it discarded the concept of "mild stimulation" altogether.

The honest framing

Of the 90 evidence-based recommendations in this guideline, none rests on high-quality evidence and only six on moderate quality.

That is not a reason to distrust it — it is the best synthesis available. But it is an argument for caution about adding interventions, rather than for filling the gap with them.

The most useful question to ask about your protocol is not "is this the best one" but "why this one for me, and what would change it".