If you had unprotected sex about one week ago, you likely still have options to prevent pregnancy. The most important factor is how many hours or days have passed since intercourse, because the most effective methods work within a 5-day (120-hour) window. Understanding where you actually are in the process will determine which options apply to you.
What “One Week Pregnant” Actually Means
Pregnancy timing is confusing because doctors count from the first day of your last menstrual period, not from the day you had sex. By that medical counting system, you’re already about two weeks “pregnant” before you even ovulate. So by the time you miss a period and take a positive test, you’re typically four weeks pregnant by medical standards, even though conception only happened about two weeks earlier.
If you had unprotected sex one week ago, you may not actually be pregnant yet. A fertilized egg takes 6 to 12 days to implant in the uterus, and a home pregnancy test won’t reliably detect pregnancy until about two weeks after conception. Testing too early can give you a false negative. This matters because your situation falls into one of two categories: either you’re still within the emergency contraception window, or you need to confirm pregnancy first and then explore your options.
Emergency Contraception Within 5 Days
If it has been 5 days (120 hours) or fewer since unprotected sex, emergency contraception can still work. There are three main types, and they differ in effectiveness and how long after sex they remain useful.
Over-the-Counter Pills
The most widely available option is a single-dose pill containing levonorgestrel (sold as Plan B and similar brands), available without a prescription at most pharmacies. It works best when taken as soon as possible. Within the first 24 hours, it prevents about 95% of expected pregnancies. That drops to 85% at 25 to 48 hours and 58% at 49 to 72 hours. After three days it still has some effect through day five, but pregnancy rates climb noticeably.
Body weight significantly affects how well this pill works. Research shows it begins losing effectiveness at around 70 kg (about 154 pounds) and may have essentially no effect for people weighing 80 kg (176 pounds) or more. At higher body weights, blood levels of the drug drop to roughly half of what lighter individuals achieve. UK clinical guidelines suggest doubling the dose for people at higher weights, but this isn’t standard practice everywhere. If weight is a concern, the two options below are more reliable.
Prescription Pill (Ulipristal Acetate)
A prescription alternative, sold as ella, works within the same 5-day window but holds its effectiveness better in those later days. Within the first three days, it performs similarly to levonorgestrel. Between days three and five, it is notably more effective. It also appears to work better for people at higher body weights, though it still requires a prescription and a quick visit or telehealth appointment.
Copper IUD
The copper IUD inserted within 5 days of unprotected sex is the single most effective form of emergency contraception. In studies, it prevented 100% of expected pregnancies when placed within that window. A hormonal IUD (the type that releases levonorgestrel directly in the uterus) also works well as emergency contraception, preventing 93% to 96% of expected pregnancies. Both require a clinic visit for insertion, but the advantage is significant: they’re far more reliable than pills regardless of body weight, and they double as long-term contraception for years afterward.
If the 5-Day Window Has Passed
If more than five days have passed since unprotected sex, emergency contraception is no longer an option. At this point, you’ll need to wait and take a pregnancy test. Home tests are about 99% accurate when used at the right time, which is roughly two weeks after conception, or around the time you’d expect your next period. Testing earlier than that risks a false negative because hormone levels haven’t risen high enough to detect.
If the test is positive, medication abortion is available up to 10 weeks of gestation (70 days from the first day of your last period). This involves two medications taken in sequence. The first blocks a hormone the pregnancy needs to continue. The second, taken 24 to 48 hours later, causes the uterus to empty. At very early stages, the process is similar to a heavy period with cramping. A healthcare provider can confirm your gestational age and walk you through the process, which in many areas can be done through a telehealth visit.
Access to medication abortion varies by state and country. In areas where it’s available, some providers can prescribe it as early as the pregnancy is confirmed, which can be just a few weeks after conception.
Side Effects to Expect
Emergency contraceptive pills commonly cause nausea, headache, fatigue, and breast tenderness. These symptoms typically resolve within a day or two. Your next period may arrive up to a week late, which can cause anxiety. If your period doesn’t come within three weeks of taking the pill, take a pregnancy test.
For medication abortion, expect cramping and bleeding heavier than a normal period, often with clots. This typically peaks within a few hours of taking the second medication and tapers over the following days, though lighter bleeding can continue for one to two weeks.
Signs That Need Medical Attention
After taking emergency contraception or early abortion medication, certain symptoms warrant a call to a healthcare provider: heavy bleeding combined with stomach pain, or ongoing spotting and irregular bleeding that doesn’t resolve. These can be signs of an ectopic pregnancy, where a fertilized egg implants outside the uterus, which requires prompt treatment. Soaking through more than two thick pads per hour for two or more hours, a fever lasting more than 24 hours, or severe pain that doesn’t respond to over-the-counter pain relief are also reasons to seek care.
Choosing the Right Option for Your Timeline
- Within 24 hours: Any emergency contraceptive pill works well. A copper IUD is the most effective choice if you can get an appointment quickly.
- 1 to 3 days: Levonorgestrel pills and ulipristal acetate have similar effectiveness. For people over 70 kg, ulipristal acetate or a copper IUD is the better choice.
- 3 to 5 days: Ulipristal acetate outperforms levonorgestrel in this window. A copper IUD remains the most reliable option at any point in the 5-day range.
- 6 to 7 days: Emergency contraception is no longer effective. Wait to test for pregnancy around the time of your expected period, then explore medication abortion if the test is positive.
The single most important variable is speed. Every hour matters with emergency contraception. If you’re within the window and unsure which method to pursue, taking an over-the-counter levonorgestrel pill immediately while arranging a clinic visit for an IUD or prescription is a reasonable approach, though you should not take ulipristal acetate after already taking levonorgestrel, as they can interfere with each other.