Clexane injections during IVF treatment – do you really need them? What do they do? And do the benefits outweigh the risks? Clexane is a powerful drug, and an expensive one. Most fertility patents don’t need it. Read on to find out why.
First, the case for. Clexane may help fertility patients with antiphospholipid syndrome. But does it work as a routine IVF add-on to boost implantation rates or reduce the miscarriage risk? Not really, the latest studies say.
Here’s fertility patients need to know.
What is Clexane?
Clexane is a brand name for enoxaparin, an anticoagulant (blood thinner). Another brand name is Lovenox. It’s part of the low-molecular-weight-heparin family known as LMWHs.
Enoxaparin (Clexane) doesn’t literally thin the blood. It simply reduces its ability to clot. Outside fertility, it’s often used to treat or reduce the risk of deep vein thrombosis. You may have read about DVT and long-haul flights – and emergency Clexane addressing the problem.
Clexane is applied as a subcutaneous injection, usually into the fatty tissue of the lower abdomen. Patients can easily administer it themselves. Those who’ve had IVF using their own eggs are, of course, used to injecting in this area.
Why is Clexane prescribed during IVF?
There are two main reasons for using Clexane in a fertility cycle:
- Preventing a blood clot. It may be wise to take it if you previously had a dangerous blood clot, have thrombosis, or develop ovarian hyperstimulation syndrome (OHSS) after IVF stimulation.
- Improving the odds of implantation and/or preventing miscarriage. The evidence for its effectiveness is mixed.
We know that IVF can increase the blood-clot risk, particularly in a post-IVF pregnancy. However, the risk is quite low. But OHSS raises the clot risk much more, should an IVF patient be unlucky enough to develop it. A large study into the management of OHSS saw blood clots in around 1.7% of IVF patients. Statistically, that’s quite a lot.
We also know that medicated frozen embryo cycles, where high doses of estrogen are used, can increase thrombotic risk markers. In other words, care should be taken with estrogen doses in FET cycles. It’s not uncommon for clinics to include Clexane in FET cycles when high daily doses of estradiol are used – even if the patient doesn’t have any thrombophilic issues.
Does Clexane improve IVF implantation?
The idea of using a strong blood thinner, like Clexane, to guard against tiny placental clots that might affect implantation is interesting. That doesn’t mean it works.
ESHRE looked at LMWH in the context of recurrent implantation failure. It found no boost in live births or clinical pregnancies for patients with at least three previous embryo transfer failures. Its verdict was blunt: LMWH (which includes Clexane) isn’t routinely advised for implantation issues.
That doesn’t mean Clexane can’t help for specific medical reasons. It’s just saying that implantation failure isn’t usually a blood-thickness problem. Clexane can’t fix a problem that rarely exists.
Clexane and antiphospholipid syndrome – in more detail
Antiphospholipid syndrome, or APS, is an autoimmune blood-clotting disorder. It’s been linked to recurrent pregnancy loss and other pregnancy complications. This is one area where Clexane can help in the context of fertility.
There’s some useful ASRM guidance on APS and recurrent pregnancy loss. It recommends baby aspirin and heparin (Clexane, essentially) for APS patients. It concludes that pregnant patients with APS who take both have fewer miscarriages and higher live birth rates. It points out that APS can be life-threatening in pregnancy. So, their support is clear.
ESHRE concurs. In its recurrent pregnancy loss guidance on APS, it suggests testing for APS after two pregnancy losses. If confirmed, and if the patient has additional pregnancy losses, low-dose aspirin and heparin is advised from the pre-conception stage.
Every patent is different, so always speak to your doctor or clinic about APS and whether Clexane is suitable for you. Testing is essential first.
Clexane and inherited thrombophilia
Inherited thrombophilia conditions include Factor V Leiden, the prothrombin gene mutation and deficiencies involving protein C, protein S or antithrombin. Having any of these doesn’t mean Clexane will help.
This was confirmed in a study looking at recurrent miscarriage, thrombophilia and heparin. Heparin was given to women who’d suffered two or mor pregnancy losses and had inherited thrombophilia. Taking heparin made a negligible difference to live birth rates. The study’s conclusion? There’s no compelling reason to screen for inherited thrombophilia in all women with recurrent pregnancy loss.
The ASRM rejects anticoagulant use for recurrent pregnancy loss linked to hereditary thrombophilia. (We assume APS patients are excluded.) It echoed the findings of the study: routine inherited-thrombophilia testing for every patient with a history of pregnancy loss isn’t necessary.
Cam Clexane tackle unexplained recurrent miscarriage?
The key word here is unexplained – a frustrating word many fertility patients are familiar with. Can Clexane be used to guard against another miscarriage? The research isn’t clear-cut. Let’s look at two studies.
A 2024 study into LMWH and unexplained recurrent miscarriages found no benefit in taking it. It should be stressed that the study didn’t include women with thrombophilia. This went against some past studies that saw a possible benefit. It called for further studies.
A 2025 meta-analysis into LMWH and recurrent pregnancy loss saw a few more positives. One was that enoxaparin (Clexane) was the best LMWH to take – especially at a daily dosage of 20 mg daily – in terms of increasing live birth rates. A second was that it reduced the risk of pre-eclampsia and pre-term births.
However, its reviewed trials covering multiple populations, treatments and patient types. This makes it hard to know which sub-groups of patients truly benefit – for example. fertility patients.
So, Clexane isn’t usually recommended as a routine medication for unexplained recurrent miscarriage. The judgement on its use in individual cases falls to your doctor or clinic.
What about Clexane as part of the Bondi Protocol?
The Bondi Protocol combines Clexane with a steroid like Prednisolone. It’s primarily aimed at certain patients with repeated IVF failure and high NK-cell activity. It became popular, if controversial, after encouraging results from early trials.
Its catchy name may give the study more weight than it deserves. It’s been criticised in some quarters for a lack of compelling evidence, since the study wasn’t a randomized large-scale one. The other main concern is that a combination of protocols makes it harder to identify which medication really helps.
More recent studies haven’t found a benefit from taking LMWH for implantation failure. Steroids also have their own risks. So, the two together? Many remain sceptical of the immune-therapy aspect of the Bondi study.
When do Clexane injections start and stop?
There are no set rules, though it’s likely to be one injection daily – at the same time each day. Depending on your situation, you might start the injections during stimulation, from the date of your embryo transfer, after a positive HCG result, or later.
Treatment may stop after the first trimester, continue throughout pregnancy, or even extend after birth. However, for most fertility patients who are prescribed Clexane, stopping it dead at 12 weeks pregnant is common.
The dose depends on your specific situation, and whether the use of Clexane in your case is preventative or medically necessary. 20-mg and 40-mg daily dosages are common. Your clinic will advise.
Clexane side effects and injection tips
Bruising and stinging are common side effects of Clexane. IVF patients will have injected in the same lower-abdomen area before, so will be familiar with the redness and mild discomfort.
To make injections easier, here are five tips:
- Ask your clinic for advice.
- Inject at least 5 cm from your belly button – no closer.
- Alternate sides each day.
- Pinch the skin fold as you inject.
- Don’t rub the area afterwards.
Clexane and fertility – in summary
Clexane is a good medication to take during fertility treatment when there’s a clear medical reason for it. However, based on the current evidence, it’s not needed for most implantation issues or as a miscarriage preventer.
If your clinic suggests it, ask them why – and for the potential benefits and risks in your case.
Frequently asked questions
What does Clexane do in IVF treatment?
Clexane reduces the blood’s ability to clot. During IVF, it may be prescribed to prevent thrombosis in a high-risk patient or, more controversially, as an add-on treatment to support implantation or reduce the risk of a miscarriage.
Does Clexane increase IVF success rates?
In most cases, no. Current ESHRE recommendations don’t support it solely to increase pregnancy or live birth rates after recurrent implantation failure. It may still be prescribed for a diagnosed clotting condition or when there’s a significant thrombosis risk.
Can Clexane prevent miscarriage?
Clexane can be given to patients with antiphospholipid syndrome, usually alongside low-dose aspirin. Away from APS, there’s no compelling evidence that routine use of Clexane for unexplained recurrent miscarriages, or inherited thrombophilia, improves live-birth rates.
Is Clexane safe during pregnancy?
LMWH doesn’t cross the placenta, so it’s generally safe in pregnancy. The main concern is bleeding. Treatment must still be considered on a case-by-case basis. Most fertility patients won’t see any benefit.
When should I start Clexane during an IVF cycle?
Timing depends on why it’s being prescribed. A clinic may start Clexane during stimulation, on embryo transfer day, or after a positive pregnancy test. There’s no standardised start date for fertility patients.
How long do fertility patients take Clexane for?
Most protocols stop Clexane after a negative pregnancy test. After a positive result, it’s often continued until you’re 12 weeks pregnant. However, other patients take it throughout pregnancy and even after birth. Your doctor or clinic will advise.
What dose of Clexane is used for fertility treatment?
Doses of 20 mg or 40 mg per day are often used, but your specific dose will depend on your medical situation, weight, thrombosis history and other factors. Be guided by your clinic. Always take the dose you’re instructed to take.
Why does a Clexane injection bruise?
The Clexane needle can damage tiny vessels beneath the skin. Alternate injection sites, avoid existing bruises and don’t rub the area afterwards. Contact your clinic if you experience excessive bruising or bleeding.
Can I take aspirin with Clexane?
Sometimes – like in specialist treatment for obstetric APS. Combining two medicines that change clotting activity can increase the bleeding risk. Only take aspirin with Clexane when your fertility clinic prescribes both.
What happens if I miss a Clexane injection?
Follow the instructions from your clinic, and/or read the information leaflet supplied with the product. Don’t apply a double dose unless a doctor explicitly tells you to. It’s a strong drug: handle with care.
33 Responses
A tip for using clexane from my hematologist – press really hard on the injection site. It minimizes the bruising
A tip for using clexane from my hematologist – press really hard on the injection site. It minimizes the bruising
I’m taking clexane after embryo transfer but no progesterone was prescribed. Will be a problem if progesterone is not taken
Hey did you have a succesful pregnancy. I have miscarried 3 times and now on my 4th pregnancy and just started clexane 20mg
Hi Samantha, I started clexane injections after recurrent miscarriages during.my ivf journey and gave birth to my beautiful baby girl in August 2021. I did another transfer this year and started clexane 40mg straight away and am now 28w with twins xx
From which week you started clexane injection I had recurrent miscarriage problem and I am 4 + week pregnant when should I started clexane kindly guide me
Que hermoso! Te inyectaste clexane todo el embarazo ?
I struggle massively with administering the fragmin. Why can’t it be produced using a smaller, thinner, user friendly needle?
I am going through DE transfer treatment and have been prescribed Clexane amongst other meds. I have a blood clotting deficiency meaning my blood doesnt clot quick enough so blood thinners are a big no no for me. discussed with my IVF doctor and she maintains i should just follow the treatment protocol which feel to me as a “one size fits all” approach. Due to issues ive had in the past i am reluctant to start clexane but also dont want to mess up this treatment. any advise would be appreciated.
Doesn’t sound like your dr should have done this. What is your update?
hi i need to know how many dose does a person need to take?
Hi I have done about 4 embryo transfers using DE. In two of the transfers I got pregnant but miscarried. They suddenly just stop. This time I was on both clexane 40 and aspirin. It sounded a bit too much. I am prone to thrombophilia but not V Leiden. I found my self in the night I wasn’t able to breathe kind of like a panic attack. Also I was having really bad contraction of the uterus a week after clexane and had some sort of orange fluid leaking.
After year of marriage uncontrolled relations we started to try fertilization, that took many attempts and just when my wife used Clexane she got pregnant of twins. After the babies were born we didn’t care about protection, as we knew she would “never” get that luck again. At some time (2 years) she had a thrombophlebitis and the doctor prescribed Clexane again, and what happened? She got pregnant again, without any treatment except Clexane. After the big news I ran for a vasectomy !
Congratulations Luciano, this is a beautiful story.
Me and my fiancé have had multiple IVF failures, with recurrent miscarriages.
I will be starting aspirin and Clexane soon for the 1st time so hearing this gives me so much hope and reassurance. 😊🙏
I took it during my pregnancy and ended up having premature loss. I’m glad o won’t be on it next time. It’s the only thing that my consultant to attribute to why I went into labour. It’s useful if you have a clotting disorder, but otherwise I strongly believe more research is needed on the link if clexane and pregnancy.
Hi ,
My wife has 3 times miscarriage. NOW After 4th time conceived our IVF doctor prescribed clexane 40 mg injection daily and Pregnyle Once Weekly.
Wife is 5wk pregnant..So I want to to how many days to take both injection and is it safe and avoid miscarriage problem
Hi, i took clexane on my 12 weeks pf pregnancy until one day before my delivery. And i also consume aspirin as my Doc’s suggestions.
Clexane due to my recurrent miscariage of 3 times.
Hi
I have had 2 miscarriages in the past & 1 successful ivf pregnancy where i used clexane until a day before labour
Last month tried home insemination and got a positive pregnancy result but ended in a chemical pregnancy.
Done home insemenation yesterday again. Do i use clexane now to help with implantation or when a positive pregnancy result is received?
Hi,
I have the same problem, 3 miscariages and now I take Clexane injection every day. Now I have 32 weeks.
My question is how you did delivery? Natural or cezarian and how many weeks did you rich?
Thanks
I’ve been advised that I can stop taking clexane 40mg when I hit 12 weeks (in 1.5 weeks). Though I can see a lot of women used it until labour… I am worried if I stop it may cause issues – anyone else stopped after first trimester ??
Hi did you stop taking your celexane in the end?
I stopped taking it with my 2nd son at 12 weeks but my consultant said I shouldn’t of stopped it
can u please let me know when u stop taking claxane
Did you stop taking clexane in 12 week? And after stopping it your pregnancy was successful or not?
Hi my first pregnancy was intera utrine death due to placenta abruption my blood pressure was high n iugr baby now in second pregnancy my dr start clexane 400mg n asprin 150mg
After 3 miscarriages in 2020 I went through blood tests and was found to have antiphospholipid Syndrome (blood clotting disorder).
Pregnant again now in may 2021 currently 8 weeks and ive started taking clexane 40mg and asprin 75mg as soon as I had the faintest positive (around 3 weeks pregnant). Everything looking good so far, had a scan at 7 weeks.
I have heard lots of success stories and clexane sounds like a miracle drug!
Hi, congratulations!! I have had a similar past. How long are you told to take aspirin and Clexane injections?
Thanks
Did you have a successful pregnancy?
I didn’t have any indicated symptom of blood clot. My phospholipid test and lupus anticoagulant test were negative but my DR still prescribed Clexane (daily dose of 400 mg) plus aspirin. Despite transferring the best grade (5AA) of embryo I still had a miscarriage at 5 weeks. Any advice whether I should take Clexane during my next embryo transfer? The DR who gave a second opinion said using it without any indicated symptom might result in an opposite outcome and he commented that this is a dangerous drug that could cause bleeding in the brain.
Does anyone know of I can take omega 369 and pomegranate juice. I’ve read somewhere it can interact with clexane.
I started Clexane 40mg injections after recurrent miscarriages in 2020. We didn’t change my fertility medications at all I.was on puregon and Utrogestan. I finally gave birth to a beautiful baby girl in Aug 2021 after starting clexane injections. I then went for another single embryo transfer this year 2022 and am now 28 weeks pregnant with twins and have been on clexane injections since my transfer. The only difference between all my cycles is clexane injections.
Have had 3 miscarriages and a single preterm twins, I’m now 32 weeks pregnant on clexane 40 and asprin, i wanted to know which week is best for delivery and how many weeks did you deliver , natural or scissor?
Hi, 13 Dpo and embryo transfer today I did bhcg test it is 18.4 my Dr told to stop clexane immediately..I want to know should I continue for some more days or till my 2nd bhcg…plz guide
Please any one who had taken klexane 40 mg from day 1 start of medication for ivf up till embryo transfer and after embryo transfer? Asking because I want to know if it safe. Your answers Will help me please . Thank you