1 weeks pregnant: the size of a not yet conceived
Pregnancy is dated from the first day of your last period, so in week 1 you are menstruating and your body is preparing to ovulate.
Reviewed against ACOG, NHS and WHO guidance · Updated November 2026
Typical size
—
3% of the way to your due date
Your baby this week
Pregnancy is dated from the first day of your last period, so in week 1 you are menstruating and your body is preparing to ovulate.
Your body this week
A normal period. Your body releases hormones that prepare an egg to mature.
Tip for week 1
Start a daily prenatal vitamin with 400 mcg folic acid now if you are trying to conceive.
Carry this guide in your pocket
Mamivaa is a free pregnancy app with a week-by-week tracker, vitamin and water reminders, a food scanner and a baby checklist.
Start freeThis guide offers general information and does not replace advice from your doctor or midwife. If something feels wrong, contact your provider or emergency services.