06 Oct Estrogen – why do fertility patients need it?
Estrogen supplements during IVF? They’re sometimes prescribed. And they’re essential for women having donor eggs, donor embryos or frozen-embryo transfers. So why do some doctors, and the leaflets in the packs, scare fertility patients by claiming estrogen can be dangerous during pregnancy? It’s hardly the best news to give would-be mums. Here’s the truth about the role estrogen plays before and after fertility treatment.
Estrogen helps to grow and maintain your endometrial lining and sustain a pregnancy. It also helps your placenta function, boosts blood flow to your uterus and primes your body for breastfeeding. In an IVF cycle, FSH medication (e.g. Menopur and Gonal-f) creates multiple follicles. Estrogen production is then stimulated, causing the uterine lining to thicken.
By the time of your trigger shot, your estradiol levels are sky-high. But let’s face it, IVF medication upsets your body’s reproductive rhythms. Some research suggests estrogen supplements late in an IVF cycle improve pregnancy rates by stabilising the uterine lining. Other studies say it’s not needed. Get your doctor’s view.
Estrogen is certainly needed during fresh donor-egg cycles. Thickening your endometrial lining after your depot injection is mandatory. Depot injections down-regulate your ovaries, affecting your natural estrogen and progesterone production.
Oral estrogen pills (e.g Progynova and Estrofem), typically 6 mg per day, are the norm. Their start date forms part of the synchronisation between your and your donor’s cycle. A lining scan at least three days before your donor’s egg retrieval gives you time to adjust your estrogen intake.
If your lining is too thin, an extra 2 mg, or even 4 mg, may be suggested. Anything more than 10 mg daily may need Clexane support to thin your blood. Vaginal insertion of those extra pills is common: estradiol heads faster to your reproductive organs that way. Oral pills take the slow road via your liver.
You want a 7-mm lining, and ideally an 8-mm one, by your donor’s egg retrieval day. That’s the day you start your progesterone supplementation. Your lining won’t thicken any more after that.
So what’s the deal with estrogen and FETs? Once again, estrogen is needed to grow your lining and keep it thick. Because a reasonably high dose of estrogen is taken from day 2 of your cycle in an FET protocol, the hormone is a down-regulator and prevents ovulation. So your ovaries won’t interfere with the embryos you put back in.
But no ovarian activity means no natural estrogen. So, as for fresh donor eggs, you need artificial estrogen support until at least week nine of your pregnancy. Your clinic should tell you how to reduce your estrogen (and progesterone) from the 8-week mark or so.
Occasionally, patients just don’t respond well to estrogen pills. And women with a past history of cancer are sometimes told not to take them. In this case, embryo transfer during a natural-cycle FET may be best.
You’ll take no estrogens at all from the start of your natural bleed. Then you’ll have a scan around day 10 to see if your body’s natural estrogen has plumped up your lining sufficiently. If it has, and if we see good natural follicle growth, you’ll take a trigger shot to disperse the follicles and start your progesterone support a few days later. Embryo transfer will be five days after that.
Estrogen pills are commonly dispensed as Estrofem, Progynova, Provames, Climaval, Estrace and Estrimax. Patches include Estraderm and Estrahexal. A combination of pills and patches is sometimes prescribed to patients with ‘lazy’ linings.
We’ve also seen more use of estrogen gel by our clinic in recent years. For fertility patients, a 2018 study found that estrogen gel enhanced ongoing pregnancy and live birth rates compared to estrogen pills. And a 2020 study saw better endometrial thickness and fewer side effects. We predict oestrogel will be used more routinely by clinics in the future.
As for side effects, expect a few – particularly if you take your estrogen orally. Mild symptoms include headaches, nausea, fluid retention, tender breasts, irritability and mild depression.
A very small number of women risk more serious problems like chronic insomnia, stroke, blood clots and even ovarian cancer. But this is rare. For most women, estrogen has positive effects. And for fertility cycles, it’s the gateway to a successful pregnancy.