First trimester · Week 1 of pregnancy
1 weeks pregnant: body, feeding, and care
Week 1 is counted from the first day of the last menstrual period — conception has not happened yet, and the body is preparing the uterine lining.
Body and care — week 1
Week 1 is counted from the first day of the last menstrual period — conception has not happened yet, and the body is preparing the uterine lining. Development notes on this page are general education summarized from ACOG patient-education material; they describe typical development, not your pregnancy specifically. Anatomy and growth are confirmed by your own provider and ultrasounds.
This week's checklist
- Note one body question — sleep, appetite, movement, comfort — and bring it to your next prenatal visit rather than searching it at 3 AM.
- Keep prenatal appointments on the schedule your provider sets; bring your questions list.
- Anything that worries you — bleeding, pain, reduced movement later in pregnancy — goes to your provider or urgent care first, never to a website.
Week 1 questions
What is happening at 1 weeks pregnant?
Week 1 is counted from the first day of the last menstrual period — conception has not happened yet, and the body is preparing the uterine lining.
Which trimester is week 1?
Week 1 falls in the first trimester (weeks 1–13). See the first trimester hub.
How is a due date calculated?
A due date is typically estimated as 280 days (40 weeks) from the first day of the last menstrual period. It is an estimate — try the client-side due-date calculator; your provider's dating outranks it.
Educational information only — not medical advice. Every pregnancy and every baby develops on their own timeline. If you have any concern, talk to your obstetric provider or your baby's pediatrician.