you're 1 weeks pregnant.
last revised · baby is about 0.005 cm (0.00") · 0.001 g (0.00 oz)
At 1 weeks pregnant, your baby is about 0.005 cm and 0.001 g — Pregnancy is counted from your last period — there is no baby yet this week.
about the size of a…
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.
this week's highlights
- Last period start (LMP)
- Uterine lining rebuilds
- Hormones begin shifting
- Take a prenatal vitamin
how your baby looks
There's no embryo yet — these first two weeks count from your last period. Your body is simply getting ready.
body in focus
- head
- body
- hands
- feet
what's happening 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.
symptoms at 1 weeks
- 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.
gentle tips
- Start a prenatal vitamin with at least 400 mcg folic acid.
- Track your cycle so you'll know when ovulation hits.
- Cut alcohol and limit caffeine to one small cup a day.
- Stock the kitchen with iron and folate-rich foods like leafy greens and beans.
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
what to expect 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 at week 1
How big is the baby at 1 weeks?
At 1 weeks, the baby measures about 0.005 cm and weighs approximately 0.001 g (0.005 cm (0.00") · 0.001 g (0.00 oz)).
What is developing at 1 weeks?
There's no embryo yet — these first two weeks count from your last period. Key milestones this week include: Last period start (LMP); Uterine lining rebuilds; Hormones begin shifting; Take a prenatal vitamin.
What symptoms are common at 1 weeks pregnant?
You are technically not pregnant yet. Your period started this week and your uterus is shedding and rebuilding its lining for the next cycle.
What should I do at 1 weeks pregnant?
Ovulation usually happens around week 2, when conception becomes possible. Start a prenatal vitamin with at least 400 mcg folic acid. Track your cycle so you'll know when ovulation hits. Cut alcohol and limit caffeine to one small cup a day.
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.
helpful tools
- Due Date Calculator
Find your estimated due date from your last period or conception date.
- Baby Names
Start exploring names — an early, joyful ritual.
Medically aligned with guidance from WHO, NHS and ACOG. How we write.