Risks of unprotected sex: STIs and pregnancy
Sex without a condom carries several risks, including a higher likelihood of transmitting or contracting sexually transmitted infections (STIs) such as chlamydia, gonorrhoea, HIV, and syphilis. While other contraceptive methods can prevent unwanted pregnancy, condoms are especially important as they are the only method that protects against both STIs and pregnancy. Particularly in light of rising STI numbers worldwide, condoms are of special importance (ZDF, 2014).
This article explores the risks associated with sex without a condom and answers frequently asked questions such as whether it is safe to have sex without a condom if both partners have been tested. STI testing plays a key role in the early detection and prevention of infections, as it can identify asymptomatic infections that would otherwise go unnoticed and continue to spread.
Table of Contents
- Sex without a condom and sexually transmitted infections (STIs)
- Which STIs do condoms protect against?
- How else can I protect myself from STIs?
- Is sex safe if both partners are healthy?
- Can you get infected without a condom if both partners were tested?
- What to do if you had unprotected sex
- Sex without a condom and pregnancy
- Summary
Sex without a condom and sexually transmitted infections (STIs)
Sex without a condom increases the risk of sexually transmitted infections (STIs), as condoms provide a barrier that prevents contact with infected bodily fluids and mucous membranes, thereby reducing the likelihood of transmission. While they significantly reduce the risk, they do not offer complete protection against all STIs (WHO, 2024).
Which STIs do condoms protect against?
Condoms offer varying levels of protection depending on how the STI is transmitted:
| STI | Mode of transmission | Risk reduction through condoms |
|---|---|---|
| HIV | Direct mucosal contact, especially via infected semen, vaginal fluids, or blood | Up to 98% – condoms prevent the exchange of bodily fluids |
| Chlamydia and Gonorrhoea | Contact with infected semen or vaginal fluid through mucous membranes | About 85% – even small amounts can transmit via external membranes |
| Herpes and HPV | Skin-to-skin contact with infected blisters or warts | About 70% – condoms offer partial protection but may not cover all infected areas |
| Syphilis | Contact with open sores or rashes on mucous membranes or skin | 50–70% – transmission can occur outside the condom-covered area |
| Trichomoniasis | Contact with infected semen or vaginal fluids through mucous membranes | 70–80% – trichomonads may reach areas outside the condom barrier |
| Hepatitis B | Contact with infected blood, semen, or vaginal fluids through mucous membranes | Up to 90% – condoms block exchange of infectious fluids |
Condoms only offer full protection when they are used correctly and consistently—put on before any genital contact and worn properly throughout the entire act of intercourse.
How else can I protect myself from STIs?
The following measures help reduce the risk of STI transmission:
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Being in a monogamous relationship with a tested, healthy partner
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Regular STI testing for both partners
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Abstaining from sexual activity if symptoms or suspicion of infection are present
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Vaccination against certain STIs (e.g. HPV, hepatitis B)
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Proper cleaning of sex toys and not sharing them
Source: NHS, 2024
Is sex safe if both partners are healthy?
Not necessarily. Some sexually transmitted infections such as chlamydia, HPV, gonorrhoea, genital herpes, and even HIV often show no symptoms. Seemingly healthy individuals may unknowingly carry and transmit these infections. Regular testing is therefore crucial to detect infections early and prevent unintentional transmission.
Can you get infected without a condom if both partners were tested?
If both partners have recently tested negative for sexually transmitted infections (STIs) and have had no other sexual partners since, the risk of infection is low. However, a residual risk remains due to what is known as the diagnostic window. This refers to the period between infection and the point at which it can be detected through testing. During this time, the concentration of viruses or antibodies may still be too low to be detected, meaning a test could return a false-negative result even though the person is already infectious ((CDC, 2024).
When testing, it’s important to consider the timing of the last potential exposure and the length of the diagnostic window, which can vary depending on the infection. For more detailed guidance, see our blog: "When can you be tested for STIs?"
What to do if you had unprotected sex
After unprotected sex, the next steps depend on your individual situation. Important factors include whether you and your partner get tested regularly for sexually transmitted infections (STIs), whether you are in a monogamous relationship or have multiple partners, and your personal goals—such as the desire for or avoidance of pregnancy. The following measures are important to know:
- STI test: Testing for sexually transmitted infections is recommended, but it should be done at the right time, as some infections can only be reliably detected after the diagnostic window.
- HIV prevention (PEP): Post-exposure prophylaxis (PEP) can reduce the risk of HIV infection if started within 48 hours of potential exposure. This treatment requires a prescription from a doctor.
- No further sexual contact: Until test results confirm whether an infection is present, further sexual contact should be avoided to prevent possible transmission.
- Open communication: Honest communication about potential risks ensures transparency and allows for shared prevention strategies.
- Prevention next time: To minimize future risks, condoms or other protective measures should be used consistently.
- Emergency contraception: In the case of unwanted pregnancy and in the absence of other contraceptive methods, emergency contraception (“morning-after pill”) is available without a prescription in German pharmacies. It contains one of two active ingredients: levonorgestrel (effective up to 72 hours after intercourse) or ulipristal acetate (effective up to 120 hours). The morning-after pill should only be used in emergencies, as it significantly affects hormone levels and is not intended for regular use.
Source: Cleveland Clinic, 2023
Would you like to get clarity yourself?
Regular STI testing is especially advisable if you have changing sexual partners, are in a new relationship, or have had unprotected sex. Testing is also recommended if you notice unusual symptoms or simply want clarity about your sexual health. With Homed-IQ’s discreet at-home tests—such as the Chlamydia Test, the Basic 4 STI Test, or the Comprehensive STI Test—you can easily test for one or more STIs from the comfort of your own home.
Sex without a condom and pregnancy
Sex without a condom always carries the risk of pregnancy—especially during the fertile days. To prevent unwanted pregnancy, additional contraceptive methods should be used. The most common include the pill, condom, intrauterine device (IUD), and vaginal ring. However, only condoms protect against both unwanted pregnancy and sexually transmitted infections (STIs).
How high is the risk of pregnancy without a condom?
The risk of pregnancy without a condom depends heavily on the timing within the menstrual cycle. During the fertile window—about five days before and up to one day after ovulation—the likelihood of becoming pregnant is much higher. Sperm can survive in the female body for up to five days, waiting for ovulation. Outside of this time frame, the risk is lower, but never completely eliminated. If pregnancy is not desired, other contraceptive methods should always be used (Medline Plus, 2024).
Is it true that you don’t need protection during your period?
No, that is not true. Pregnancy is still possible during menstruation, although the risk is lower. Since sperm can survive in the body for up to five days, fertilisation can occur in the case of a short cycle and early ovulation.
Summary
Sex without a condom carries significant risks, as it not only increases the chance of unwanted pregnancy but also raises the risk of transmitting sexually transmitted infections (STIs) such as HIV, chlamydia, and gonorrhoea. While other contraceptive methods can prevent pregnancy, condoms are the only method that protect against both STIs and pregnancy. Regular testing and awareness of the diagnostic window are essential, as many infections are asymptomatic and can be passed on unnoticed.
