1st trimester · Week 1
1 week pregnant
Dating from your last period
Clinicians usually count pregnancy from the first day of your last menstrual period (LMP). Conception has typically not happened yet. This week is about your cycle, not an embryo.
How is your baby developing at 1 week?
There is no embryo this week. A follicle is being recruited and the uterine lining starts to rebuild after bleeding. The sesame-seed comparison is only a visual metaphor — it does not describe a baby yet.
What changes in your body at 1 week?
You may still be menstruating. Cramps, fatigue, and mood can follow your usual pattern. If you are hoping to conceive, this is a preparation week rather than a pregnancy week.
Tips for this week
If pregnancy is possible or planned, start or continue folic acid (often 400 micrograms daily, or the dose your clinician recommended). Review medicines and supplements with a clinician or pharmacist. Limit alcohol and avoid smoking. This is general information.
