pregnancy week 1
1 weeks pregnant.
Pregnancy is counted from your last period — there is no baby yet this week. Your body is preparing the lining of the uterus for ovulation and conception.
Updated 29 July 2026 · Sources: NHS and ACOG
Your baby this week
There's no embryo yet — these first two weeks count from your last period. Your body is simply getting ready.
- Last period start (LMP)
- Uterine lining rebuilds
- Hormones begin shifting
- Take a prenatal vitamin
What may be changing in your body
You are technically not pregnant yet. Your period started this week and your uterus is shedding and rebuilding its lining for the next cycle.
Period bleeding
Week 1 begins on the first day of your last period, so bleeding is the main event. It usually lasts three to seven days and is completely expected.
Menstrual cramps
The uterus contracts to shed its lining, which can feel like a dull ache or waves of cramping low in your belly. A warm compress or gentle movement often helps.
Lower back ache
Prostaglandins released during your period can cause a heavy, dragging ache across the lower back. It typically eases as the bleeding tapers off.
Mood dips
Oestrogen and progesterone are at their lowest point of the cycle, which can leave you feeling flat or irritable. Levels start climbing again within days.
Tiredness
Blood loss and hormonal lows can sap your energy this week. Iron-rich meals and an earlier night can make a noticeable difference.
Very heavy bleeding — when to call
If you are soaking through a pad every hour for several hours, or passing clots larger than a 50p coin, call your midwife, GP or doctor. That level of bleeding deserves a check.
Your week 1 checklist
- Record the first day of this period — it becomes day one of your pregnancy dating
- Begin (or continue) a daily 400 mcg folic acid supplement
- Book a preconception check-up if you have a long-term condition or take regular medication
- Check whether any current medicines are safe when trying to conceive
- Download a cycle-tracking app or mark your calendar to spot your fertile window
A useful partner move this week
Conception is a shared project, so this is a good week to look after your own health too. Cutting back on alcohol, stopping smoking and eating well for two to three months before conception can improve sperm quality. Sit down together and agree on the habits you both want to change.
What comes next
Ovulation usually happens around week 2, when conception becomes possible. Knowing your fertile window helps you time things — or simply pay attention.
Common questions
Why does pregnancy start counting from my last period?
Doctors date pregnancy from the first day of your last menstrual period because it is a date most people can pin down, whereas the exact day of conception is rarely known. It means the first two weeks of a 40-week pregnancy happen before conception. Your due date is calculated as 40 weeks from that first day of bleeding.
Can I do anything in week 1 to improve my chances of conceiving?
Yes — the groundwork weeks matter. Taking folic acid daily, keeping alcohol and caffeine low, not smoking and eating a balanced diet all support conception and early development. Tracking your cycle now also helps you identify your fertile window around week 2.
How long should I take folic acid before getting pregnant?
Ideally you would start at least one month before trying to conceive and continue through the first 12 weeks of pregnancy. Folic acid lowers the risk of neural tube defects, which form very early — often before a positive test. If you have a higher-risk history, your doctor may recommend a higher dose, so ask before increasing it yourself.
How many months is 1 weeks pregnant?
Pregnancy months do not divide evenly into weeks, so clinicians date pregnancy in weeks. At 1 weeks, you are in trimester one.