DuoStim and Random-Start IVF: Starting Stimulation Off the Usual Calendar

For most of IVF's history, stimulation started at a fixed point: the first few days of a period. That made sense biologically, because a new group of follicles becomes available at that time, and practically, because it lined everything up for a fresh transfer a couple of weeks later. Research over the past couple of decades has shown that follicles can be recruited at other points in the cycle too. That opened the door to three less familiar approaches you may now hear about at a consultation:

• Random-start stimulation: starting injections on whatever day of the cycle you happen to be on.
• Luteal-phase stimulation: deliberately starting in the second half of the cycle, after ovulation.
• Double stimulation, often called DuoStim: two stimulations and two retrievals within one menstrual cycle, the second starting shortly after the first retrieval.

This article explains what each one involves, what the European Society of Human Reproduction and Embryology says about them in its ovarian stimulation guideline (ESHRE, 2025 update), and what they mean for your plan, especially if you are travelling for treatment.

The idea behind starting at a different time

The traditional view was that one batch of follicles is recruited per cycle, at its start. A newer model, discussed widely in reproductive medicine, describes several waves of follicle development across a cycle. If follicles responsive to stimulation drugs are present at other times, then waiting for a period is not strictly necessary to start.

The catch is the uterus. Starting in the middle or second half of a cycle means the lining is out of step with a fresh transfer, and progesterone from a natural ovulation may already be present. That is why all three approaches in this article are, in practice, built around freezing eggs or embryos and transferring later.

What ESHRE's 2025 update says

The common thread is clear: these strategies are endorsed for building up eggs or embryos to freeze, not for cycles where you plan to transfer straight away.

Random-start stimulation

How it works

Injections start on the day you are ready, whatever the stage of your cycle. If you are in the first half of the cycle, the clinic may add medication to prevent the leading follicle from ovulating. If you are after ovulation, follicles can still be recruited, and the existing corpus luteum carries on making progesterone in the background. The overall stimulation and monitoring look similar to a standard cycle, though the length can vary.

Who it is used for

The best-known use is urgent fertility preservation, for example before cancer treatment, where waiting several weeks for a period could delay chemotherapy. ESHRE's guideline also mentions it for egg donors, where it is considered equally appropriate to a conventional start. Some clinics use it to fit treatment around travel or work commitments, when no fresh transfer is planned.

The safety note

ESHRE's good practice point asks clinicians to discuss the risk of OHSS if a natural conception happens. The concern is that if you were to conceive naturally in the same cycle, pregnancy hormone combined with stimulated ovaries could raise the risk of OHSS. Your clinic should tell you whether to avoid unprotected intercourse during that cycle.

Luteal-phase stimulation

This is a planned start after ovulation, rather than an opportunistic one. Because natural progesterone is high at that point, a premature LH surge is less likely, and some clinics use a progestin or other suppression strategy. The resulting embryos are frozen.

ESHRE's conditional recommendation limits it to situations where a fresh transfer is not intended and natural conception is not possible. It also says that starting stimulation in the late luteal phase with a plan for fresh transfer is probably not recommended for low responders. If a clinic proposes a luteal start with a fresh transfer, ask why.

DuoStim: two retrievals in one cycle

How it works

The first stimulation follows a conventional start. After the first retrieval, a second stimulation begins within days, recruiting a further group of follicles in the luteal phase. A second retrieval follows. Everything is frozen, either as eggs or embryos, for later use or testing.

Who it is used for

DuoStim is often discussed for people who produce few eggs per cycle and want to accumulate embryos faster, for example patients with low ovarian reserve or those planning to test embryos with PGT-A and wanting more to test. It is also considered for urgent fertility preservation. Our guide to egg banking across multiple retrievals covers the broader strategy of batching cycles, and the poor ovarian response guide covers how plans change when egg numbers are low.

What it does and does not promise

The main appeal of DuoStim is time. It can produce two retrievals in about the span of one cycle instead of two or more. ESHRE's strong recommendation is about using it to accumulate eggs or embryos when no fresh transfer is planned. It is not a way to turn a low-reserve situation into a high-reserve one, and a second retrieval does not guarantee more usable embryos. Ask your clinic what results it has seen in patients similar to you, and how it reports them.

What all three mean for your transfer

Because these strategies are designed around freezing, the transfer happens in a separate, later cycle. That transfer cycle needs its own preparation, either timed to your natural ovulation or using medication to build the lining. Our article on natural versus medicated frozen transfer explains those options.

For patients, this usually means:

• A longer total timeline to the first transfer, even though egg collection may happen sooner or more efficiently.
• Freezing and storage costs from the start.
• The chance to test embryos before transfer if you and your doctor choose PGT-A, since no fresh transfer is needed.

When these approaches are not a good fit

• When you want or need a fresh transfer in the same cycle.
• When your clinic has little experience with them; ask how often it performs each one.
• When the main motive is convenience, and the extra cost or time of a separate frozen transfer outweighs the scheduling benefit.
• When a clear medical reason for a standard start exists, such as a cyst that needs to resolve first.

Planning around travel

Non-standard starts can help people who travel for IVF, but they also introduce new logistics.

1. Random start can save a trip's worth of waiting if you arrive at an unpredictable point in your cycle and only plan to freeze. Confirm the clinic is comfortable starting on arrival.
2. DuoStim extends your stay. Two stimulations and two retrievals take longer than one standard cycle, so ask for the expected total days on site, with a buffer.
3. The transfer becomes a separate trip unless you stay for a frozen transfer cycle or ship embryos. Our guide to shipping embryos internationally explains that option.
4. Medication quantities change. A second stimulation in DuoStim needs its own supply. Make sure the clinic's medication plan covers both.

Questions to ask your clinic

• Why are you suggesting a random, luteal or double stimulation for me rather than a standard start?
• Will all eggs or embryos be frozen, and what is the plan for the transfer cycle?
• How often does your clinic use this approach, and how do your results compare with standard starts for patients like me?
• What extra medications, monitoring and procedures does it involve, and what is the full cost?
• Do I need to avoid natural conception during the stimulation cycle?

The bottom line

Random-start, luteal-phase and double stimulation free IVF from the usual calendar. ESHRE's 2025 update supports DuoStim strongly for accumulating eggs or embryos when no fresh transfer is planned, allows luteal and random starts in freeze-all situations, and treats random start as a standard option for egg donors. These are tools for specific situations: urgent preservation, low egg yield, or tight timelines. They are not upgrades for everyone, and they nearly always mean a frozen transfer later.