1 Week Pregnant
Reviewed by Safi Allah Khan
Medically reviewed by: Safi Allah Khan · Written by the Momi team · Last updated 20 October 2026
Quick answer: At 1 week pregnant, there is no baby yet. Pregnancy is counted from the first day of your last period, so weeks 1 and 2 come before conception and week 3 is when fertilisation and implantation happen. You're at the very start of the first trimester, with 39 weeks to your due date.
| Week 1 at a glance | |
|---|---|
| Trimester | First |
| Month | 1 |
| Weeks to due date | 39 |
| This week | Pregnancy dating starts with your period |
Your baby at 1 week
There is no baby yet. Week 1 is the week of your period. Pregnancy is dated from the first day of your last menstrual period because that date is easy to know, while the exact day of conception usually is not. That is why the first two weeks of a 40-week pregnancy happen before you conceive.
Your body at 1 week pregnant
You are having your period, and your body is preparing a new egg to be released later in your cycle. If you are trying to conceive, this is a good time to think about your health before pregnancy.
Things to do this week
- Start a daily folic acid supplement if you are trying to conceive. The NHS advises 400 micrograms a day before conception and until 12 weeks.
- Note the first day of this period. It is the date a due date calculator asks for.
- Talk to a doctor about any regular medicines before you try to conceive. Don't stop prescribed medicine without advice.
When to call your doctor or midwife
Contact your care team straight away if:
- you have severe pain low on one side of your belly, or pain in the tip of your shoulder, after a positive test or a late period
- you have bleeding that is heavier than spotting
- you get a positive test and take regular prescribed medicine (ask before stopping anything)
If something feels wrong, trust that feeling and call. In an emergency, call your local emergency number.
Track week 1 in Momi
If you later get a positive test, enter this period's start date in Momi and it will estimate your due date and count your weeks from here. Momi follows your pregnancy week by week with your baby's size and development, and keeps your diary, bump photos, appointments, kick counts and contractions in one place.
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Keep reading
All weeks · 2 weeks pregnant →
Sources
- ACOG Committee Opinion No. 700: Methods for Estimating the Due Date
- NHS: Signs and symptoms of pregnancy
- NHS Best Start in Life: Week-by-week guide to pregnancy
Medical disclaimer: Momi and this website provide general information, not medical advice. Always talk to your doctor or midwife; in an emergency call your local emergency number.
FAQ
Am I really pregnant at 1 week?
Not yet in the everyday sense. Doctors date pregnancy from the first day of your last period, so the first two weeks happen before conception and week 3 is when the fertilised egg implants. If you conceive this cycle, these weeks still count toward your 40.
How many months is 1 week pregnant?
1 week pregnant is in the first month of pregnancy and the first trimester. Months don't divide evenly into 40 weeks, so different sources may label the month slightly differently.
Related guides
Track this in Momi
Momi is a free pregnancy tracker app for iPhone and Android that follows pregnancy week by week, estimates the due date, and keeps a pregnancy journal, weight log, kick counter and contraction timer in one place.
