Answering this question during week 1 isn't as simple as you'd think. That's because baby hasn't been conceived yet. Confused? That's understandable. It all comes down to how your doctor dates your pregnancy.
Instead of using the date of conception, doctors use the first day of your last menstrual period to estimate your due date. This tends to be more accurate.
So your first week of pregnancy is actually your period. During this week, your body is releasing last month's egg in order to make way for next month's new egg—that's the one that will grow to be your baby! At nearly the size of a fleck of pepper*, your eggs are the largest cells in your body.
*The size information and comparisons in this article are estimates. Fetal size may vary from pregnancy to pregnancy.
Source: American Pregnancy Association
Reviewed 12/6/2023