Medications for Endometrial Preparation in FET in Thailand

Endometrial preparation is a critical step in frozen embryo transfer (FET) cycles. The goal is to synchronize the uterine lining with the embryo’s developmental stage to optimize implantation. In Thailand, clinics typically offer three main protocols: natural cycle, modified natural cycle, and medicated (hormone replacement) cycle. Each uses different medications and monitoring schedules. This article explains the common medications involved and what you should discuss with your clinic.

At a Glance: Common FET Protocols

• Natural cycle: Minimal medication; relies on your body’s own ovulation.
• Modified natural cycle: Uses hCG trigger or low-dose gonadotropins to time ovulation.
• Medicated cycle: Uses estrogen and progesterone to control the lining growth and timing.

Natural Cycle Protocol

In a natural cycle, no or minimal medications are used. The clinic monitors your natural ovulation through ultrasound and blood tests. Once ovulation is confirmed, progesterone supplementation may be given to support the luteal phase. Common medications include:

• Progesterone: Given as vaginal suppositories, injections, or oral tablets after ovulation to support the uterine lining.

This protocol is suitable for women with regular ovulatory cycles. It requires frequent monitoring to detect ovulation timing.

Modified Natural Cycle Protocol

This protocol is similar to the natural cycle but uses medications to control ovulation timing. It may involve:

• hCG trigger injection: To induce ovulation at a planned time.
• Low-dose gonadotropins (FSH/LH): Sometimes used to stimulate follicle growth if needed.
• Progesterone: Started after ovulation for luteal support.

This approach offers more scheduling flexibility while still using your own hormonal cycle.

Medicated (Hormone Replacement) Cycle Protocol

The medicated cycle uses exogenous hormones to prepare the endometrium, suppressing your natural cycle. It is often chosen for women with irregular cycles or when precise timing is needed. Medications include:

Estrogen

• Estradiol (oral, transdermal patch, or vaginal): Used to thicken the endometrial lining. Typically started on day 2-3 of the cycle and continued for about 10-14 days until the lining reaches adequate thickness (usually 7-10 mm).

Progesterone

• Progesterone (injectable, vaginal suppository, or oral): Started once the lining is ready, to transform it into a secretory phase receptive for implantation. The embryo transfer is scheduled after 5-6 days of progesterone.

GnRH Agonist (optional)

• Leuprolide acetate or similar: Sometimes used to suppress the pituitary and prevent premature ovulation, especially in women with endometriosis or other conditions.

Monitoring During Endometrial Preparation

Regardless of protocol, monitoring is essential. This typically includes:

• Transvaginal ultrasound: To measure endometrial thickness and pattern, and to check for follicle development or cysts.
• Blood tests: To measure estradiol, progesterone, and sometimes LH levels.

Your clinic will determine the frequency of monitoring based on your response.

Questions to Ask Your Clinic

• Which FET protocol do you recommend for my situation, and why?
• What medications will be used, and what are the possible side effects?
• How often will I need monitoring appointments?
• What is the typical timeline from starting medication to embryo transfer?
• Are there any specific instructions for taking the medications (e.g., timing, with or without food)?

Next Steps

• Confirm your clinic’s preferred protocol and medication regimen.
• Discuss any pre-existing conditions that may affect medication choice.
• Plan your travel and accommodation to accommodate monitoring appointments.

For more information on the overall IVF process, see our IVF in Thailand and Treatment Process pages. International patients can find additional guidance on our international patients page.

Frequently asked questions

What is the difference between natural and medicated FET cycles?

Natural cycles rely on your own ovulation with minimal medication, while medicated cycles use estrogen and progesterone to control the uterine lining growth and timing, suppressing your natural cycle. The choice depends on your menstrual regularity and clinic recommendation.

How long does endometrial preparation take for FET?

The duration varies by protocol. Natural cycles depend on your ovulation timing (usually around day 14). Medicated cycles typically involve 10-14 days of estrogen before adding progesterone, with transfer about 5-6 days later. Your clinic will provide a personalized timeline.

What are the common side effects of estrogen and progesterone?

Estrogen may cause nausea, bloating, breast tenderness, and mood changes. Progesterone can cause drowsiness, dizziness, bloating, and injection site reactions. Discuss any concerns with your doctor.

Can I travel during endometrial preparation?

Travel may be possible but requires careful planning. You will need to attend monitoring appointments (ultrasounds and blood tests) as scheduled. Discuss your travel plans with your clinic to ensure you can comply with the monitoring schedule.

Do I need to take medication after the embryo transfer?

Yes, progesterone supplementation is typically continued after transfer to support the uterine lining until the placenta takes over, usually for 8-12 weeks if pregnancy is achieved.

Continue your research

• IVF in Thailand guide
• Treatment journey
• International patient guide

Medical information notice: This article is educational and does not replace individual assessment, diagnosis, genetic counselling or treatment advice from a licensed clinician. Provider services, availability, fees and policies should be verified directly before booking.