First trimester
Pregnancy Week 1
Your baby is about the size of a not yet conceived.
Size
not yet conceived
Length
—
Weight
— g
Baby in week 1
Week 1 of pregnancy is calculated from the first day of your last menstrual period. You are not actually pregnant yet — your body is preparing for ovulation.
What you may notice this week
Period begins. Hormones reset for the new cycle.
Tips for week 1
- Start prenatal vitamins with folic acid if you're trying to conceive
- Track the first day of your period — this is your reference point
- Cut alcohol and limit caffeine
Tools that pair with this week
Due Date Calculator
Estimate your delivery date by last period or conception date. Naegele’s rule plus cycle adjustments.
Week Tracker
See exactly how many weeks and days pregnant you are, plus your trimester and key milestones.
Contraction Timer
Tap once to start, once to stop. Tracks duration, frequency, and pattern over time.
Ovulation Calculator
Find your fertile window based on your cycle length. Plan or avoid with confidence.
Baby Name Generator
Filter by origin, style, length, and starting letter. Boys, girls, and unisex.
Growth Percentile
Plot your baby’s weight, length, and head circumference against WHO percentile curves.