Your fertility, Your responsibility

Thermal contraception as a method for people with sperm

by Masl Richter, Raphi Maier, Ben Russell, Jannik Böhm

A straightforward question to you: What methods of contraception[1] for people who produce sperm do you know? Vasectomy and condom? This is the answer most people will probably give. It is not wrong. But it is not exhaustive either. Besides these popular methods, there are very talented but unfortunately little known underdogs, despite the fact that some of them have been used for centuries. This article wants to change that and explain one of these contraceptive methods. Namely, the thermal contraceptive method. But first back to the basics, to understand how the popular and lesser-known methods work.

Where do sperm actually come from?

Before a foetus can grow in the uterus, a sperm cell must merge with an ovum in the fallopian tube. At this point, the sperm has already completed a long journey. About 1000 new sperm cells are produced in the two testicles every second. But before they are ready for their journey, they mature for about two weeks in the epididymides. This process, which takes about two and a half months in total, is called spermatogenesis. After this maturation process, the sperms travel through the vas deferens to the prostate. When ejaculated, the seminal fluid, enriched by secretions from the vesicular glands, the prostate and the Cowpers’ glands, is then passed through the urethra[2].

By the way, ejaculation is still possible after a vasectomy. After all, despite a large quantity of about 100 to 300 million sperm in an average ejaculate, sperm only make up about 2% of the volume.

Contraception: a brief overview

The desire to prevent pregnancies is probably as old as humanity itself. The first recorded contraceptive attempts date back to 3000 B.C. From fish bladders to intestines, crocodile dung to cotton wool or cloth, many things were tried as a barrier between the uterus and sperm – often with only moderate success. Still today, about 48% of all pregnancies worldwide are unwanted. 61% of unintended pregnancies end in abortion[3].

Modern contraceptive methods are based on very different working principles. The condom, for example, forms a barrier between the sperm and the uterus. What sounds good in theory often does not work so well in practice. Thus, a relatively large number of unwanted pregnancies occur with the condom[4].

The vasectomy, on the other hand, is a surgical method. Here, the two vas deferens are cut and permanent infertility is achieved after about 2-6 months. Almost all other contraceptive methods have to be used by people capable of childbearing. Besides the copper or hormonal IUD, which are inserted into the uterus (the so-called intrauterine pessary methods), there are also so-called natural methods, such as the symptothermal method [5]. But also all hormonal methods, such as the pill, the ring, the patch and so on, count to this.

No matter how the hormones are taken, they are pharmaceutical products and an intervention in bodily processes that can be associated with side effects such as headaches, increased risk of thrombosis and cardiovascular disease, and decreased libido.

Research into methods for people with sperm has been going on for as long as for people with uterus. Hormonal contraception for people with sperm, for example, already exists and is used. So far, however, no product has reached market maturity. From gels for application to injections to tablets, different application schemes are basically possible.[6]

A different approach was invented by Klemens Bimek. His invention is a switch that can be installed in the vas deferens and blocks the sperm’s path. The switch can be easily turned on to (temporarily) restore fertility if desired. A similar approach is taken by RISUG or the so-called vasal gel. A gel injected into both vas deferens forms an impenetrable plug for sperm. The gel can be liquefied again by another injection and fertility is subsequently restored. Similarly unknown, although some have been used for centuries and also already in evidence-based research: herbal remedies. Turmeric, field mint, papaya, essences of the neem tree or even the cotton plant contain contraceptive active ingredients.

A recently published master’s thesis by Rebecca Weiss, a design student from Munich, caused a sensation and attracted international attention[7]. She proposes a contraceptive called COSO, which uses the thermal method (see below) with the help of ultrasound waves. What all these methods have in common is that they are not available, or only to a very limited extent. Moreover, there is not yet sufficient scientific evidence. Market approval can therefore be expected in five to ten years at the earliest.

But all hope is not lost. In the following, we will introduce you to an effective and easy-to-use method: the thermal contraceptive method.

WTF is thermal contraception?

Like the development of eggs, the development of sperm also follows a hormonal cycle. This cycle lasts about 60-70 days and sperm production takes place in the testicles. The testicles are located outside the body because sperm production requires a temperature that is slightly lower than the body temperature. If the temperature of the testicles is systematically increased by at least 2° C over a longer period of time, sperm production stops. This effect can be used for contraceptive purposes – we will explain exactly how. The more the testicles are heated, the shorter the heat application must be to achieve the desired result. After the regular application of heat has ended, sperm production recovers completely after about 2-9 months[8]. If there is a plan to have a child, another contraceptive method should be used during this recovery period. The only side effect of thermal contraception observed is a slight and harmless reduction in the size of the testicles.

Generally, a distinction can be made between two types of application: on the one hand, the temperature increase can be caused by the body’s own temperature, on the other hand, external heat sources can be used for this purpose.

Heating with the body’s own heat

As early as the 1960s, the American John Rock, who was involved in the development of the birth control pill for people with uteruses, was researching the thermal contraceptive method for people with testicles. In the 1970s, feminist groups in France took up the use of thermal contraception using the body’s own temperature. The research contributions of Roger Mieusset and Jean-Claude Soufir are particularly important for this method of application. They developed the so-called Thermal Contraception Protocol (CMT). Currently, there are a few self-organised groups in France (e.g. ARDECOM, Garçon, Thomas Boulou), Germany (Kollektiv Unverhütbar from Leipzig) and Austria (kollektiv kontrazeption) that are working to spread this method [9]. With this application option, the testicles are pushed upwards into the abdominal cavity, more precisely into the inguinal canal. Then they have to be held in place there. This is completely painless. The testicles can be held in place with a so-called slip chauffant, a jockstrap (a suspensor without a hard shell) with a hole through which the penis and the “empty” scrotum are passed. The ring of fabric around the hole holds the testicles in the inguinal canal. Instructions for sewing a slip chauffant can be found here [10].

A second possibility to keep the testicles in the inguinal canal is the so-called Andro-Switch by Thoreme[11]. The penis and scrotum are also passed through this silicone ring and the ring is then placed close to the body. The ribbed surface ensures that the ring does not slip off and the testicles “fall out” again[12]. As the temperature rise is not as strong with this method (approx. 1.5-2 °C), thermal contraception using body temperature should be used the entire waking time or for at least 15 hours a day[13].

Heating with auxiliaries

Water bathing
Already in the 1930s, the doctor Martha Vögeli in India developed application protocols for thermal contraception with regular sitting baths in very warm water (up to 48°C or 45°C for 45 minutes). In the 1980s, a group of Zurich autonomists made use of the findings on testicular bathing and set up a study and also their own laboratory structures [14]. Currently, more research is being done on the water bath method at Chinese universities.

Heating pad
Another way to heat the testicles is to apply heat externally through a heating pad. The pants called SpermaPause[15] have a sewn-in compartment for such a hand-sized heating pad, which is powered by a small rechargeable battery stowed at waist height. Because the heat pad warms the testicles more than is possible using your own body temperature, it does not need to be used for as long. Four hours per day is recommended as a minimum. 

Effectiveness and reliability

It all sounds pretty easy at first, doesn’t it? But seriously, does it really work?

The scientific evidence[16] on thermal contraception is fairly good, but comprehensive long-term clinical studies are still lacking. Therefore, it has not yet been possible to calculate a Pearl Index[17]. Possible very rare side effects have not been recorded and reversibility for a period longer than four years has not been researched. So far, 539 ovulation cycles have been observed in various studies in 50 couples who could potentially become pregnant and who used only thermal contraception. Only one unintended pregnancy occurred. However, the person later stated that they had not worn the ring for seven weeks.

The previously presented methods can be used in a complementary way. For example, we have found that it makes sense to always have an AndroSwitch or slip chauffant with you in case there is no power socket nearby. For example, when hiking or travelling.

According to the sellers of the heating pad, the application can be interrupted for a day without losing the contraceptive effect. The reversibility of the method is currently proven for a maximum of four years of uninterrupted use[18]. It is relatively easy to check whether a person is using the method correctly and whether the contraceptive threshold has been underrun after about 2-3 months of uninterrupted use by means of a spermiogram[19]. It is recommended to have a spermiogram approximately every 3 months during the contraceptive period to check for infertility. Once the use of the method has been stopped, the recovery of fertility can also be checked with a spermiogram. There is currently no commonly accepted contraceptive threshold for the combination of the various relevant sperm parameters (e.g. sperm count per ml, motility, count of normally formed sperm). Studies to date suggest that a sperm count of less than 3 million sperm per milliliter has higher contraceptive efficacy than the use of a condom[20]. However, experts currently discuss a count of less than 1 million sperm per milliliter ejaculate as a target for highly effective contraceptives for people with sperm[21].

It is important for us to emphasise that thermal contraception does not protect against sexually transmitted infections. Therefore, this method does not replace regular testing and the use of condoms.

Social context or: Why don’t I know about it?

For people with sperm, the condom and vasectomy are considered the only effective means of contraception. Vasectomy is often linked to reaching a certain age (in Austria, the age of 25) and must be medically argued with a completed family planning. In fact, it is very difficult to find doctors who perform vasectomies on childless people under 35. All this reinforces the belief in the condom as an alternative.

Most people with sperm are cis men. It is mostly heterosexual interactions where pregnancies can occur. “Come on, condoms are impractical, unsexy and putting them on interferes with the flow of sex. Plus, it feels so much better to me without a condom.” Many cis men argue like this or something similar. In this argumentation, one’s own pleasure is placed above the physical integrity of the other person.

These narratives contribute to a situation where it is easy for many hetero cis men to hide their laziness and irresponsibility behind a seemingly unchangeable “reality”. This leads to a situation where the responsibility for preventing pregnancy is given solely to people with childbearing capacity and they are subsequently left to deal with it on their own. The psychological and physical consequences of an unwanted pregnancy, namely abortion or pregnancy and birth, are largely borne by people who are able to give birth. Patriarchal gender norms still assign tasks such as child care to so-called women. This allows hetero cis men to escape the consequences of their irresponsible ejaculations more easily. In addition, this reality is justified with male phantasms such as the untouchability of the testicles, while uteri are equipped with IUDs without question.

While most young persons with uterus are taken to gynaecologists to be told about all possible contraceptive methods at best, but are usually prescribed the pill quite quickly without any consultation, most urologists and androlgists do not even know about the existence of alternative contraceptive methods for people with sperm. Instead, alternative methods are sometimes even discouraged, if they are even mentioned at all. Existing study results are ignored (mostly they have not been read) and in other cases the side effects of (hormonal) contraceptive methods are willingly accepted.

Once again, and this is important to us: there are complemetary methods and alternatives to the condom and the vasectomy. Thermal contraception is curremntly available. It is non-invasive and a medium- to long-term method, i.e. mistakes cannot happen every time it is used. From more than 2 years of practice, we can also say for ourselves: it is effective, easy to control and absolutely painless. The cost of the product is relatively low and in winter we are usually nice and warm. Thermal contraception, whether in the form of the Andro-Switch or a heat pad in your pants, makes it possible to control your own fertility in the long term and and counteracts the contraceptive imbalance.

My body, my fertility, my responsibility.

[1] Contraception means in this article the prevention of pregnancies.

[2] For further information on the anatomy and reproductive processes of people with a penis, we recommend the brochure “wie geht’s – wie steht’s?” from the BZgA or First Love.

[3] Jonathan Bearak et al., “Unintended pregnancy and abortion by income, region, and the legal status of abortion: estimates from a comprehensive model for 1990–2019”, The Lancet Global Health, 8.9 (2020), e1152–61

[4] The Pearl Index (assessment measure for the effectiveness of contraceptives: the lower, the more effective) of condoms is given as up to 12. This is mainly due to incorrect application. For example, very few people with a penis bother to buy condoms in a suitable size (e.g. on

[5] With the symptothermal method, several factors are documented, such as the consistency of the cervical mucus, tightening in the breast and other symptoms. The infertile days can then be determined. On these days, potentially impregnating sexual practices can be carried out without using other contraceptive methods. The method requires some discipline and is only suitable for relatively regular daily routines, since, for example, drunken party nights and days can falsify the symptoms.



[8] Y. X. Liu, “Temperature control of spermatogenesis and prospect of male contraception”, Frontiers in Bioscience, S2.2 (2010), 97; Roger Mieusset, “Temperature and testis”, Encyclopedia of Reproduction, 1.1970 (2018), 573–78

[9] So also the author group of this text.

[10] Sewing instructions


[12] Video explaining the function of the Andro-Switch:

[13] On 10.12.21, the French Drug Agency temporarily stopped the sale of Andro-Switch. The reason given was the lack of CE certification (which can only be obtained through very expensive approval procedures).

[14] You can find their study results at the following link:


[16] CN: The research we cite speaks of men and women. We distance ourselves from these naturalizations. You can find a collection of scientific sources on thermal contraception here.

[17] The Pearl Index is the assessment measure for the effectiveness of contraceptives.

[18] J. C. Soufir and R. Mieusset, “Guide pratique d’une contraception masculine hormonale ou thermique”, Andrologie, 22.3 (2012), 211–15,

[19] In a spermiogram, the semen is examined for its quality, such as the number of living sperm, their motility, etc. Health insurances usually do not cover the costs in the case of a check of the contraceptive reliability.

[20] Eberhard Nieschlag, „Clinical trials in male hormonal contraception“, Contraception, 82.5 (2010), 457–70,

[21] P. Aaltonen u. a., „10th Summit Meeting Consensus: Recommendations for Regulatory Approval for Hormonal Male Contraception“, Journal of Andrology, 28.3 (2006), 362–63,

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