IVF treatment involves various protocols, each designed to suit different patient needs. One of the available options is Progestin Primed Ovarian Stimulation (PPOS), which replaces certain injections with oral medication to prevent premature ovulation.
What is Progestin Primed Ovarian Stimulation (PPOS)?
In vitro fertilisation (IVF) requires controlled stimulation of the ovaries to produce multiple eggs. A standard IVF cycle includes medications that:
- Stimulate egg growth – Follicle Stimulating Hormone (FSH) helps develop multiple follicles.
- Prevent early ovulation – GnRH antagonist injections block premature egg release.
PPOS replaces the GnRH antagonist injections with oral progestin tablets, reducing the number of injections required during stimulation.
How PPOS Differs from Conventional IVF Protocols
In a standard IVF stimulation cycle, daily injections suppress natural ovulation. With PPOS, patients take progestin tablets instead, avoiding 5–7 injections over the cycle.
Reasons Why PPOS is Used in IVF
1. Reduces Number of Injections and Medication Costs
Since PPOS does not require GnRH antagonist injections, patients may experience fewer injections and a lower total medication cost.
2. Similar Success Rates to Conventional Protocols
Studies comparing PPOS with conventional IVF protocols indicate no major differences in:
- Number of eggs retrieved
- Embryo quality
- Pregnancy rates
- Baby health outcomes
3. Often Recommended for Fertility Preservation
PPOS is commonly used in fertility preservation cases, such as:
- Egg freezing for future use
- Fertility protection before cancer treatment
- Patients at risk of Ovarian Hyperstimulation Syndrome (OHSS)
4. Considered Safe for IVF Treatment
Research suggests PPOS is as safe as conventional IVF. Patients undergoing this protocol do not face increased risks compared to those following standard treatments.
Limitations of PPOS in IVF Treatment
The main limitation of PPOS is that fresh embryo transfer is not an option in the same cycle.
Why Can’t Fresh Embryo Transfer Be Done?
Progestin tablets affect the uterine lining, making it less receptive to embryo implantation. As a result, all embryos must be frozen and transferred in a later cycle using a frozen embryo transfer (FET).
When is PPOS Recommended?
PPOS may be suitable for:
- Patients undergoing egg freezing – Focuses only on egg retrieval.
- Fertility preservation before cancer treatment – Protects future reproductive options.
- Patients at risk of OHSS – Reduces complications related to hormone-sensitive conditions.
- Cases where fresh embryo transfer is not planned – If the cycle is already set for frozen embryo transfer, PPOS may be an option.
However, those who prefer fresh embryo transfer may need to consider other IVF protocols.
Comparison: PPOS vs. Conventional IVF
| Factor | PPOS | Conventional IVF |
| Number of injections | Fewer | More (daily GnRH antagonist injections) |
| Medication cost | Lower | Higher |
| Safety | Similar to conventional IVF | Safe |
| Embryo transfer | Frozen transfer only | Fresh or frozen transfer |
| Commonly used for | Egg freezing, OHSS risk, fertility preservation | Patients who prefer fresh transfer |
Is PPOS the Right IVF Protocol for You?
Progestin Primed Ovarian Stimulation (PPOS) is one of the available options in IVF treatment. It may be suitable for patients who need to freeze embryos or want to reduce injections.
Meet Our Fertility Specialists
Dr Chua Ka-Hee
Consultant Obstetrician & Gynaecologist, Fertility Specialist
MBBS (Singapore), MRCOG (UK)
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