AuthorisedTherapeutic use (Phase IV)Interventional

Reproductive outcomes with letrozole co-treatment during ovarian stimulation in women with endometriosis undergoing IVF/ICSI: a randomised, multicentre, parallel group pragmatic trial

This research is investigating whether adding a medication called letrozole to the usual IVF/ICSI treatment can improve the chances of women with endometriosis having a baby. Endometriosis can make it harder to get pregnant, and this study aims to see if letrozole makes a difference. We will be looking at how many women have a live birth after one full IVF/ICSI cycle, including both fresh and any frozen embryos from that cycle. Researchers will also check other important things like pregnancy rates, miscarriage rates, and any complications during pregnancy or childbirth, as well as the baby's health. The study involves many clinics and will help doctors understand the best ways to help women with endometriosis become pregnant.

At a glance

Status

Authorised

Phase

Therapeutic use (Phase IV)

Sponsor

UZ Brussel

Enrolment target

854

Start

13 May 2026

Women with endometriosis undergoing IVF/ICSI

What is this study about?

This study is a special kind of research looking into how we can help women with endometriosis who are trying to get pregnant using IVF (In Vitro Fertilisation) or ICSI (Intracytoplasmic Sperm Injection). Endometriosis is a condition where tissue similar to the lining of the womb grows outside of it, which can sometimes make it harder to conceive.

Doctors want to find out if adding a medicine called letrozole to the usual IVF/ICSI treatment helps more women with endometriosis have a live birth. Letrozole is a medication sometimes used in fertility treatments to encourage egg development. This study is designed to be very thorough, checking not just whether a pregnancy happens, but also if it leads to a healthy live birth, which is the main goal.

We'll be looking carefully at many things throughout the process. This includes how many healthy babies are born per IVF cycle, how many attempts it takes, and if there are any miscarriages or other problems during pregnancy or after the baby is born. We also want to understand if adding letrozole affects the mother's comfort during treatment or her overall quality of life. The aim is to gather strong evidence to help doctors make the best decisions for their patients.

Key takeaways

This study explores adding letrozole to IVF/ICSI for women with endometriosis.
The main goal is to see if it helps more women have a live birth.
It's a large, multi-centre study to get clear, reliable results.
You would be in one of two groups: letrozole plus standard care, or standard care only.
Detailed information on pregnancy, birth, and baby's health will be collected.
You have the right to leave the study at any time.

Who may be eligible?

This study is looking for women who are planning to have IVF or ICSI treatment because they have endometriosis. You need to be at least 18 years old to take part. There isn't an upper age limit mentioned, but typically fertility treatments have age guidelines.

To see if this study might be right for you, your fertility specialist will review your full medical history and current treatment plan. They will be able to confirm if you meet all the necessary requirements to participate in this particular research.

Could this study suit you?

Answer these quick questions to see if you may be eligible. This is a guide only — the research team makes the final call.

Are you a woman?
Are you aged 18 or over?
Are you having IVF or ICSI treatment?
Do you have a diagnosis of endometriosis?
Are you willing for your treatment outcomes to be followed for up to one year?

Answer every question to see your result.

What does participation involve?

If you join this study, you will go through a normal IVF/ICSI treatment cycle. You would be randomly chosen to either receive the letrozole alongside your usual treatment or just continue with your standard treatment, like tossing a coin. You won't know which group you're in, and neither will your doctors.

The study involves monitoring your fertility treatment as usual, which includes regular clinic visits for scans and blood tests. Researchers will collect information about your egg collection, embryo transfers (both fresh and any frozen ones from the same cycle), and track your pregnancy journey. This also includes following up on the birth of your baby and their initial health. They will also ask about your pain levels and quality of life at specific points. The main part of the study tracks outcomes for up to one year after you start treatment.

Potential risks and benefits

Taking part in this study means you'll receive careful monitoring throughout your IVF/ICSI treatment, which could be beneficial. The potential benefit is that for some women with endometriosis, combining letrozole with IVF/ICSI might improve the chances of having a live birth. However, there's always a chance that the treatment might not work, or that adding letrozole might not make a difference, or could even have its own side effects, which your doctor will discuss with you. You are free to withdraw from the study at any time, for any reason, without it affecting your medical care.

Locations (1)

Some site locations are approximate. We're improving this — please verify with the trial team before travelling.

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Unverified
Belgium

Common questions

What is endometriosis?

Endometriosis is a condition where tissue similar to the lining of the womb grows elsewhere in the body, often causing pain and sometimes affecting fertility.

What is IVF/ICSI?

IVF (In Vitro Fertilisation) and ICSI (Intracytoplasmic Sperm Injection) are types of fertility treatment where eggs are fertilised with sperm outside the body.

What is letrozole?

Letrozole is a medication sometimes used in fertility treatments to help encourage eggs to develop in the ovaries.

Will I know if I'm getting letrozole or not?

No, this is a 'blinded' study, meaning neither you nor your doctors will know if you're receiving letrozole or standard treatment. This helps ensure fair results.

How long does the study last for me?

The study will track your outcomes for up to one year from when you start your IVF/ICSI cycle, including any pregnancies and births.