Week 1 of Pregnancy
Not yet pregnant. This is the week of your last menstrual period — clinically counted as week 1 because the actual conception date is rarely known.
Fetal size
Seed stage
- Length
- Not yet measurable
- Weight
- Not yet measurable
Fetal development
- No conception yet. The uterine lining is shedding during menstruation.
- Ovaries begin maturing follicles for the next ovulation.
Maternal changes
- You are menstruating. Gestational age is counted from the first day of the last period (LMP).
- A daily 400–800µg folic acid supplement helps prevent neural tube defects if conception occurs.
Recommended checkups
- If you have had preconception counseling, continue the prenatal vitamins and lifestyle changes your clinician recommended.
Jump to week
Textbook averages. Individual variation is wide and this is not medical advice — confirm with your OB.