If your clinic prescribes estrogen as part of your IVF treatment, frozen embryo transfer or donor-egg cycle, it does so for good reason. Estrogen helps prepare the uterus for implantation and supports the early weeks of pregnancy.
For many fertility patients, estrogen plays a key role in building the endometrial lining and controlling treatment timing, it helps create the optimal environment for an incoming embryo. Dosage, application and duration depend on the type of treatment you choose and your clinic’s approach.
The role of estrogen in fertility treatment
Estrogen is most often prescribed as pills (a common brand is Progynova). It’s one of two hormones that prepare your uterus. In fertility treatment, it boosts the endometrium to the desired thickness, The lining needs to be structurally correct, too – ideally trilaminar.
Estrogen works in tandem with progesterone. In a normal menstrual cycle, your ovaries make estrogen. But with fertility treatment, that natural process is often suppressed or bypassed. To ensure stable estrogen levels, your clinic may therefore turn to estradiol – the more medical term for estrogen.
So, estrogen builds the lining, Progesterone makes it super-receptive. Both matter. But estrogen does the heavy lifting first. It’s then joined, a few weeks, by its partner hormone, progesterone.
Is estrogen used in every IVF cycle?
No. In a fresh IVF cycle, ovaries usually produce good amounts of estrogen. So many IVF patients don’t need any more. But some do – if their lining, hormones or general prognosis require it..
Estrogen shines in fully medicated cycles: frozen embryo transfers (FETs), donor-egg cycles and embryo adoption. The aim is to control and nurture the endometrium very purposefully, rather than rely on natural, ovarian-led hormones. If you’re down-regulated using a depot injection, as many donor-egg recipients are, estrogen is a must.
Why estrogen is usually prescribed for frozen embryo transfers
In a medicated FET, you’ll typically start estrogen early in your cycle (day 2 or 3) before progesterone is added. Once the latter starts, the lining shifts into implantation mode and doesn’t keep grow much more.
So, estrogen effectively stands in for the hormones the ovaries would normally produce. You need enough estrogen for things to work properly. Two low a dose may not grow the lining enough or sufficiently bypass ovarian function. Too high a dose could result in a lining that’s too thick.
Estrogen support lasts well into early pregnancy until the developing placenta takes over hormone production. In natural-cycle FETs, no synthetic estrogen is used. Patients here typically take a trigger shot, plus a small amount of progesterone after that.
Which is better: a medicated or natural-cycle FET? The argument over the most effective endometrial preparation is ongoing. But the general consensus is that both approaches can work well. However, if a patient is known to respond poorly, or react badly, to estrogen, a natural-cycle FET may be the only option. Natural FETs are often cheaper, with fewer side effects.
Why donor-egg patients need estrogen in IVF
For donor-egg patients on a fresh cycle, estrogen is essential. Why? Because a donor recipient’s cycle is synchronised with their donor’s cycle. Natural ovulation won’t happen, so the uterus must be medically prepared. Clinics manage a donor recipient’s cycle more aggressively, routinely turning ovarian function off, via the depot injection, before starting estrogen.
So, with the dual strategy of depot + estrogen, the endometrium is ready at exactly the right time for the donor’s egg retrieval. (That date is also the start of the progesterone phase.) The timing of the recipient’s embryo transfer a few days later is therefore also put in place.
With the ovaries silent, estrogen rebuilds the lining from scratch. Think of a fresh donor egg cycle as medicated and fully controlled, with synthetic estrogen the essential fuel for optimising the endometrium.
How estrogen is taken during fertility treatment
Estrogen can be prescribed in several forms, The common ones are pills (oral, sometimes vaginal), patches and gel. Clinic preference varies. Many choose pills, adjusting the dosage as necessary if the lining response is slow.
At the monitoring ultrasound scan – usually on day 10 to 12 of the estradiol phase – a lining less than 7 mm may extra estrogen. Vaginal pills can be very effective here.
Patches or gel, often prescribed to patients with known side effects or a poor response to oral estrogen, are also effective. Both can be seen as a gentler approach than oral pills. They avoid the need for, and metabolic complexity of, absorption via the liver.
Researchers compared oral, vaginal, and transdermal options. One study found that transdermal products led to better lining thickness and fewer side effects than vaginal estrogen. Another found that estrogen gel had a positive effect on pregnancy and live birth rates.
Does a thicker lining always mean better results?
Patients are often told that a lining between 8 mm and 12 mm is best before the progesterone phase – in fresh and frozen cycles. That’s generally true, but there’s room for movement.
A recent major study on optimal endometrial thickness found some interesting data. First, that lining thicknesses below 6 mm was linked to a big drop in live birth rates. Second, that in fresh cycles, a thicker lining up to 12 mm improved outcomes. And third, that in frozen cycles, a 7 mm lining is no less optimal than a lining between 7 mm and 10 mm.
Away from the data, many patients conceive with imperfect linings. And others, whose linings are optimal, don’t achieve a pregnancy. So lining growth, helped by estrogen, matters. But it doesn’t guarantee success.
How long do you stay on estrogen after transfer?
In medicated FETs and donor cycles, varying degrees of down-regulation take place. Estrogen is therefore continued through much of the first trimester. Why? Because, as discussed, hormonal support, including progesterone, sustains the pregnancy until the placenta is able to take over. This is around the eighth week of pregnancy.
Many clinics taper estrogen and progesterone gradually – over a week or two – rather than abruptly stopping it. Medication reduction used to start around week 11 or 12. These days, many clinics start earlier. The thinking is that weaning off IVF meds just after placental activity begins makes for a smoother transition.
And what about estrogen before embryo transfer? In FETs, transfers usually happen between on day 19, 20 or 21. But a study into the duration of estrogen in FET endometrial preparation showed that estrogen intake can be longer. However, progesterone duration prior to transfer can’t be extended like this.
What if you can’t take estrogen or don’t respond well to it?
Some patients don’t tolerate estrogen. Others have a medical history that requires caution, such as patients with clotting disorders or a history of hormone-sensitive cancer.
A natural-cycle FET may be the answer here. Alternatively. some estrogen formats, like gel, may be more appropriate for those with certain thrombophilic disorders. Speak to your clinic.
Side effects of estrogen in IVF and fertility treatment
Most estrogen side effects are mild. Common ones include:
- headaches
- nausea
- bloating or fluid retention
- breast tenderness
- mood changes
- tiredness
These can be more pronounced when using oral estrogen. Many patients have no side effects at all. Serious complications, like blood clots, are uncommon, but tell your clinic if you have a history of thrombosis, aura migraines, or other risk factors. Blood thinners like Clexane may help certain patients.
In summary
For many fertility patients, estrogen makes treatment possible. It helps build the endometrial lining, ensures a carefully timed embryo transfer, and supports early pregnancy when the body’s natural hormones are displaced.
Some patients do worry about side effects. But in IVF, egg donation, embryo adoption, and medicated FETs, estrogen is used with a clear objective: to prime the uterine environment for implantation and ongoing pregnancy. The rewards outweigh the risks.
Your questions answered
Estrogen is prescribed to help build and maintain the endometrial lining so an embryo has a better chance of implanting. It’s most commonly used in medicated frozen embryo transfers, donor-egg cycles, and donor-embryo treatment.
No. In fresh IVF cycles, your ovaries often make plenty of estrogen during stimulation. Extra estrogen is more commonly needed when the cycle is being medically controlled, such as in a frozen embryo transfer or donor treatment.
Estrogen encourages the womb lining to thicken and become receptive. In simple terms, it helps prepare the ‘bed’ the embryo will implant into before progesterone takes over and supports the next stage of lining development.
Many clinics like to see an endometrial thickness of around 7 mm or more before starting progesterone, but there’s no perfect universal number. Thickness matters, but it’s only one factor in overall implantation potential.
In a medicated FET, yes, it often is. That’s because synthetic estrogen is doing the job your ovaries would normally do naturally, helping prepare and maintain the lining before and after embryo transfer.
That depends on your clinic protocol, but many patients in medicated cycles continue estrogen into the early weeks of pregnancy until the placenta is ready to take over hormone production. Always follow your clinic’s exact tapering plan. These days, medication reduction often starts earlier than it used to.
The most common side effects are headaches, nausea, bloating, breast tenderness, tiredness, and mood changes. Some patients find patches or gel easier to tolerate, although the best option depends on your clinic’s approach.
Not necessarily better for everyone, but they may suit some patients more. Research suggests transdermal or vaginal routes can provide good lining support, and that they may reduce some side effects compared with oral pills in certain cases.
Sometimes, yes. In a natural or modified natural-FET cycle, your body produces its own estrogen, and the clinic times transfer around your ovulation. This can be a good option for some patients.
The leaflet can sound alarming, but it covers wide-ranging uses and risk groups. In fertility treatment, estrogen is prescribed in a specific, monitored way for a set amount of time. If you have a blood disorder or a complex medical history, make sure your doctor knows.
54 Responses
Nicely explained
Thank you.
This is clearly explained and really cleared out any worries I had.
Thanks – this has really helped me as I started taking progynova orally on 31/12 and my clinic has been closed for the holidays. Once they reopen tomorrow I’m going to request a not oral version, hopefully this will help with the headaches & tears!
I am on fresh egg donor transfer cycle and I didnt have period for 4 months before the cycle. The doc put me on 75ml patches (every 72 hours) for 10 days, my lining has increased from 5.3mm (before patch) to 13mm and I still have to wait for another 10 days to have embryo transfer. I had thick lining history in the past so now the doc told me to change to use pill 2mg only a day. Does it sound correct? I had two failed egg donor cycles already and I had 15mm thickness first time and 21mm second time, my clinic still asked me to go ahead but failed, I never had three lines patterns and I am concerned if my endometrium is not good enough for implantation. I had done hysteroscopy nothing was found. I am confused if I should carry on with this cycle. Could please help? Many thanks
Hi Emily.
I’m sorry you have gone through so much. I see your post is from February. I’m just curious to know how things have gone for you? I hope all is well. And I still wishing you the best of luck.
Hi, my doctor has subscribe me progynova 2mg, 3 times a day. I was reading the side effects and some of them was breast or ovarian cancer, stroke or heart attack. This has really scared me from start taking it and the doctor did not even explain this to me or did not even asked for my previous medical history. I saffer from panic attacks. Should I take them ot not?
I am very scared of side effects. Thanks
It is only when a patient is consistently exposed to estrogen that the risk of endometrial cancer or cardiovascular side effect increase. Occasional exposure as the case in an FET cycle may not warrant panic. However you are correct that your doctor should have allayed your fear by pre -empting your question. Relax and continue your medication.
Hi,
I am on 6mg Estrofem a day which will continue the next 2 weeks until my next visit at the IVF clinic. I do however feel very sick from the pills. I have vomited 3 times today and feel very sick. Due to circumstances I cant get in contact with my IVF clinic. Is this normal and should I continue to take the pills – I really dont feel like taking anymore pills right now.
Thanks
I’m on Progynova 6mg a day and I too thought that was what was making me so sick and asked my dr to switch me to the patches. However she says I’m at too delicate a stage to switch (9 weeks) so I’m having to resort to keeping taking it and taking anti sickness tablets instead. I have to say I really felt like the Progynova was the issue and my friends who used patches said they were never actually sick (whereas I’m vomiting violently twice each morning). yet another example of something I wish I had known BEFORE I started treatment as sounds like I could have gone onto patches if I had raised this earlier.
Hi Kylie. I dont have an answer for that. I was on 6mg/day, and now I’m on 4mg/day of Estrace. I just wanted to tell you to hang in there and I hope all goes well for you during your transfer. I wish you the best and stay positive. Good luck.
Thanks for sharing it very informative.
Thanks for explaining the side effects of estrogen. Make me feel much better that it is actually ” normal” the way your body sometimes feel.
I’m still breast feeding my baby boy who is 1year and 8 months old.. Will estradiol secreted through breast milk and affect my baby if I get it for FER
I’m still breast feeding my baby who is 1year old. Will estradiol affect my baby if I get 6mg/daily?
I start progynova 6mm daily and often 10 day my lyinig is 2m what can I used to help
Can I ask have you had any side effects to the progenova
Hi,
I am due to have a FET on the 11.08.17. I am having this done overseas however I’ve took 12mg of estrofem for the first two days then 8 mg on day 3, then 2 mg on day 4 and then 6 mg therefore. The doctor did not prescribe me 12mg at once I made the mistake of taking 6 tablets instead of 6mg. I am still planning on going ahead with the transfer. Anybody with any such experience of a high dosage at the beginning? Should I be scard?
Hi, I’m pregnant and have been asked to take 2mg of Progynova twice a day. We conceived through IUI. Does anyone know if it’s recommended to continue after pregnancy? I keep reading information that we should not take it if you’re pregnant. Any advice would be great. Thanks
Hi, pls for how many days did u took the progynova before confirmation of pregnancy
Hi I have been taking estradiol 2mg since my IVF Transfer. I have cramps and tender breast. I was hoping that this was a sign that I am pregnant. Can someone help me. I go for my 2 weeks test on the 19th to see if I am. Could these just be symptoms?
How did it go?
I am currently on my 2W wait period as well and I am experiencing the same symptoms, but
I read that they could be due the estradiol and progesterone. They both have similar side effects and could be the same as pregnancy symptoms.
donot worry n dnt keep guessing whtr u vil get ur prriod or u r pregnanat..because both symptoms r d same…so just relax n enjoy ur self n be happy..
I had my FET on 23rd Sept.. doc prescribed me 4mg PROGYNOVA thrice a day, duphaston 2mg twice a day, Susten- 400 vaginal BD.. also sustem 100 mg inj alternate day… moreover taking folvite & ecospirin once daily…Need to have 2ww for beta HCG… NO symptoms of pregnancy till now, is it good or not good ?
Heyy Hii i m going through same phase had my Fet on 11th Feb n my doc suggested same Medicn which u hav told Plzz let me know wat happen to u I mean u got positive or???
Hi..i am prescribed with the same meds. I am under 2ww. What is your outcome?
I am taking 6mg of progynova per day for a FET. During yesterday, day 3, I developed abdominal pain. I thought it would dissipate overnight but I am still in pain this morning. Any comments appreciated. Thanks
Hi
We are supposed to have embryo transfer in 3 days
My wife is currently taken 4 tabs of estrofem per day the thing is she took it today 8 hours earlier!!
Se tried to vomit and no pill came out just some water
Plz help what to do?
Hi, I just finish progynova, ovaries are resting, no cysts and the endometrium is 5 mm, good news i will start tomorrow the stimulation. However, last night i have small cramps, is it normal?
On successful IVF OD(at present) 6 weeks,doctor have told to continue for 3 more weeks & then to stop,what side effect I can expect on stopping?
I have gone through ivf cycle with donar eggs and it is positive. My doctor advised me to take estradiol 24 mg daily but by mistake I was taking 12 mg daily. Just today I came to know (6 week 6 days) pregnant. I am worried and afraid will it harm my fetus.
I’ve been taking on ovreena 30mg and now have been given progynova 2mg daily. I’m wondering if the dosage is low. I’m also taking vitamins b12 1000mg of fish oil clonfolic & soya isoflavins . I have not been given a date for fet yet. I’m worried I’m not getting enough info from my overseas clinic
Ii am on progynova 2 and on day 12 i was suggested for TVS but i started bleeding.
I’m 4 weeks pregnant through IVF first attempt,
However I’m on progynova 2 mg , 3 per day ,
In my 3rd week I started spotting and StI’ll is .Sometimes my joints hurt and get really weak ,
at times I get cramping in the pelvic ..
Has anyone experienced this ?
Hi there!I had my son thru IVF.I was spotting after 3th week,for a 2 weeks.My Dr.told me that is normal in some women .And joint pain is normsl as well.Your body is adjusting to pregnancy.I had shooting pain in my pelvic,it was expanding.
Good luck
Hi,hv been on progynova 2mg too prayers for a successful pregnancy.
Dear Dr.
My last ivf cycle was failed and d14 after ET
Was negative .dr said ct estrogen and progesterone for another 3 days and rpt test in after 3days .today 20th day also beta hcg was negative.
Dear dr
Can you explain after stopped homone therapy just can be ovulate(wich start yo grow with previous induction) prior to menstruation
Thank you
Janaki
Hi I had my First IVF transfer with two embryos on Wednesday 28/11/2018, Today is my 2day ET but I don’t have any symptom can some help please or is it too early to complain?
I did my EFT on 20/03/2019. First fresh cycle failed. Im on estrofem now 6mg. My test is on the 29th I can’t help it nerves are killing me. The last time I did not cope well with the negative result.
I’m on Progynova 2mg, 6mg a day and I am 9 weeks pregnant, however I am vomiting 6-7 times a day not only morning but anytime including midnight. I believe it is Progynova that is causing me vomitting so badly I can’t eat anything not even drink water. So I skipped one pill and missed second Progynova for a day then I could eat for dinner first time.. Can I take 4mg rather than 6mg a day instead? Otherwise my baby won’t have rnough nutrition as I vomit so badly..
I am 3 weeks pregnant..doctor told me to have progynova even after pregnancy…is it safer to have it..I read many articles that it is not safe
In early pregnancy….I am so worried…could u guide me pls
I was on estradiol tablets for almost 2weeks due to FET preparation but I stop as the FET did not take place. However, I have been waiting for my period and is overdue for almost 13days. Please is it normal to have such a long delay after having stopping estradiol tablets?
I was just on Estrogen as well also to prepare for FET. On day 10 she said that everything looked good so far and to come back next week. A follicle was seen on Day 10. I could see it myself. Next appointment she told me it had to be canceled as the local hospital will not do FET on Easter !! Why didn’t they just tell me that from the start, so that I don’t take medications that I don’t need. Hang in there.
I just had a hysteroscopy after the doctor said that my lining is thin. So he recommends progynova 2mg, two times a day for one month.
Hi there,
I just saw your post, I just had a hysterscopy and have to take 2mg estrace, I’m just curious did you end up getting pregnant and were you able to do a fet after? And if so how long
Thanks for any advice I know this is an old comment
Shannon
Hi am taking Estradiol 2mg. My lining is now 6mm and I was advised to continue for another three days. My question is that what if my lining is over 8mm, would that be normal and will they still continue with the transfer.
Hi, I know you posted this years ago but I just wanted to add a reply in case other readers are concerned about this too. Over 8mm is definitely ok and actually good as 7-8 is the baseline for lining. The thicker the better. When you get close to 40mm that is when you will be too thick and at risk of bleeding.
I had my transfer of fresh egg donor egg on 22 of March 2019. Doc. Prescribed 2mg 3 times daily, progesterone injection 100mg a day and progesterone 400mg pessaries. I only have headaches, little tiredness,salivary mouth for a day or two. In fact am just as healthy as I went to do the IVF with donor eggs. No serious symptoms of pregnancy. It this normal.
I had egg donor ivf tranfer and got positive from 10th day of transfer i got started itching and redishness on my body so doctor advised me to stop progynova
So can pregnancy grow naturally ..
Im in early pregnancy of 5 weeks . Doctor suggests me to take progynova 2mg twice a day as i was taking ovigyn D3 before conceiving. Is it safe to take the med.
Can i reduce my estrogen intake on my own wirhout letting doxtor know before transfer …
I am trying to concieve.today is my 11 th dy and my egg size is 15mm and uterus lining is 6mm. Doc suggested me to intake 2mg estradiol valerate tablets thrice a day. Is it ok to intake thrice a day.(total 10 tab)
Hi, I’ll be having an FET procedure by April, my period just started tonight, and it says on my protocol that I need to take the oestrogen tablet on the 2nd day of my cycle but unfortunately the medicine I ordered from Czech have not arrived today, it will be delivered on Monday but don’t know what time it will come, and this will mean that I have missed two days of my oestrogen pills. Will this affect my FET?
Hi. Thanks for the article, it’s very helpful. I wanted to find something about taking Estrofem before the day #1 of the cycle. My doctor prescribed it to me saying that it will help to prime my body for the IVF cycle, making the eggs being mature at the same time (so it has nothing to do with uterus line). But I need to taking them 1 week before my periods presumly starts. I may be pregnant without knowing (because I’m still trying to get pregnant naturally) and I’m afraid of the effects it may cause in this case.
Well explained. Thank you so much for all that you do.