How early can you tell you’re pregnant?

For most people, the first clear sign is a missed period. Early tests can pick up some pregnancies a few days before that, and some people notice symptoms around the same time, but nothing is certain until you get a positive test.

How pregnancy weeks are counted

Pregnancy is dated from the first day of your last period, not from when you had sex. So in a 28-day cycle, you conceive at about 2 weeks pregnant, and you’re 4 weeks pregnant on the day your next period is due. When you read that symptoms start ‘at 4 to 6 weeks’, that’s counted from your last period too.

What has to happen first

After an egg is fertilised, it takes several days to travel to your womb. Once it implants, usually 6 to 12 days after ovulation, it starts making hCG, the hormone tests detect. It takes a few more days to build up. That’s why you can’t tell straight after sex. Our day-by-day guide explains each step.

The timeline

Here’s how it usually goes in a 28-day cycle. If your cycle is longer or shorter, everything moves with it.

The days after sex. Nothing to notice. Sperm can survive for up to 7 days, so conception can happen several days after you had sex.
About a week after conception. The fertilised egg implants in your womb, usually 6 to 12 days after ovulation. You won’t feel it happen. Some people notice light spotting or mild cramps around the time their period is due, but it isn’t certain these are caused by implantation, and many people notice nothing.
From about 5 days before your period is due (about 10 days after ovulation). The earliest you can use an early test. It picks up some pregnancies, but not all.
The day your period is due (4 weeks pregnant). The day most tests are designed for. A missed period is often one of the first signs.
4 to 6 weeks. When symptoms usually start, if you get them.

The earliest signs

A missed period. If your cycle is regular, this is often one of the first signs. Some people have a much lighter bleed or spotting around the time their period is due instead, often called implantation bleeding, though it isn’t certain that implantation is what causes it. If you could be pregnant, get any bleeding checked.
Breast changes. Your breasts may get larger and feel tender, just as they might before a period. Tommy’s says the veins may be more visible and your nipples may darken.
Tiredness. Feeling extremely tired after doing your usual daily activities.
Feeling or being sick. This can happen at any time of day, and most people start noticing it at around 4 to 6 weeks.
Cramping, a bit like period pains.
Needing to pee more often than usual, without pain or discomfort.
Changes in taste and smell. A metallic taste in your mouth, being sensitive to certain smells, cravings for new foods or losing interest in foods you usually enjoy.
Other changes, like more vaginal discharge without soreness or irritation, constipation, and mood changes.

To start with, you may not have any symptoms at all, and every pregnancy is different. Many of these signs also feel just like the days before a period, so on their own they can’t tell you. See pregnancy or PMS?

The earliest you can test

Some early tests can be used from 5 days before your period is due (the packet may say ‘6 days before your missed period’), but they won’t pick up every pregnancy that early. Testing from the day your period is due is more reliable, though a negative can still be wrong if there isn’t enough hCG yet. If your period doesn’t come, test again a few days later.

For more detail, see how early can I take a pregnancy test?

If your contraception changes your periods

If you use contraception that stops your periods or makes them irregular, a missed period isn’t a reliable sign. If you think your contraception might have failed, or you’ve had unprotected sex, take a test at least 21 days after the sex.

If you’re having fertility treatment

If you’re having fertility treatment, test on the date your clinic gives you. Testing early may give a false result. Your clinic will tell you what to do next.

What about apps and smartwatches?

Some wearables track changes in temperature and heart rate that can hint at pregnancy, but they can’t confirm it. A test is still the way to know. See can a smartwatch tell you’re pregnant?

Questions people ask

Can you tell you’re pregnant a week after sex?

No. A week after sex, a fertilised egg may only just be implanting, and your body won’t have made enough hCG for any test to find. Any symptoms you notice then are much more likely to be pre-period ones.

Can you have pregnancy symptoms before a missed period?

Some people do, but early pregnancy symptoms usually start around 4 to 6 weeks of pregnancy, which is around the time your period is due or after it. Before that, they’re very hard to tell apart from the days before a period.

Can you be pregnant and have no symptoms?

Yes. The NHS says you may not have any symptoms at all to start with, and not everyone gets every symptom.

I’ve had a period but still feel pregnant. What should I do?

If the bleed was lighter or shorter than usual, take a test. See pregnancy-like symptoms during your period.

When to get help

Mild cramps that ease with rest are usually nothing to worry about. But if you’re pregnant, or think you could be, get urgent advice from your maternity unit, an early pregnancy unit or NHS 111 if you have:

any bleeding or spotting, even if it’s light
tummy pain that’s severe, on one side, or hasn’t eased after resting for 30 to 60 minutes
pain in the tip of your shoulder

Call 999 if you have bleeding along with severe tummy pain, pain in your shoulder, or feeling sick, faint or dizzy, or if the bleeding is heavy (soaking a pad soon after putting it on). Also call 999 if you have sudden, sharp and intense tummy pain and you feel very dizzy or faint, feel sick or look very pale. These can be signs of an ectopic pregnancy or a miscarriage that need treating straight away.