Pregnancy Week 1: How the Weeks Are Counted
It may sound strange, but pregnancy week 1 begins on the first day of your last period, even though there’s no pregnancy yet at that point. That’s how doctors count the weeks, and understanding it will save you a lot of headaches from now on. Let me explain it calmly ❤️.
⚠️ Haven’t taken a test yet or already got a positive? If you have a missed period or a positive test, you’re probably in week 4 or beyond, not week 1. You can work out your week or go straight to pregnancy week 4.
Why is week 1 counted from your period?
For a very practical reason: the date of your last menstrual period (what doctors call your LMP) is the only date you can know for sure. Nobody knows the exact day of ovulation or fertilisation, so the first day of your last period is taken as the starting point.
This way, a pregnancy is counted as 40 weeks from your last period: ovulation happens around week 2, fertilisation in week 3, and implantation with the first symptoms in week 4.
What happens in pregnancy week 1?
Medically, in week 1 you’re having your period: the uterus is shedding the lining from the previous cycle and your body is already preparing for a new one. At this point there’s no fertilised egg, so you’re not pregnant yet, even if the calendar says “pregnancy week 1”.
What starts now is the countdown: in a few days you’ll ovulate (week 2) and, if you have unprotected sex during your fertile days, conception can happen.
Is it normal for a test to be negative in week 1?
Pregnancy tests detect the hCG hormone, which only starts being produced after implantation (around week 4). That’s why in week 1 a test will always be negative: there’s nothing to detect yet. If you take one too early, you’ll only get an unnecessary worry.
When can I take a pregnancy test?
Ideally, wait until the first day of your missed period, which is usually the start of week 5. If you don’t want to wait, a blood test (beta-hCG) can detect a pregnancy from about 10-12 days after conception. In the meantime, you can take our free online pregnancy test to get some guidance from your symptoms. And if you fancy a bit of fun, try your luck with our fun fingerprint game — it’s just a game, not a real test.
How do I know which week I’m really in?
To find out your exact week, use the date of your last period. You can use the calculator in our pregnancy week by week section and, once your doctor confirms your week, just look up that week. If you’re waiting for a test result or a period, continue with week 2, where I explain when ovulation is most likely.
Remember this article is for information only. If you have any questions about your health or your cycle, consult your doctor, who’s the best person to guide you ❤️.
