Week-by-Week Your 40-Week Pregnancy Journey
Pregnancy is often described as lasting 40 weeks. Each week brings meaningful changes — both in your baby’s development and in your body. Understanding pregnancy week by week can help you feel prepared, informed, and connected as your baby grows.
If you would like to return to the Pregnancy guide, visit the Pregnancy hub.
Pregnancy Topics
How Pregnancy Weeks Are Counted
Pregnancy is measured from the first day of your last menstrual period (LMP), even though conception typically occurs about two weeks later. Gestational age helps healthcare providers monitor development and schedule tests appropriately.
This means:
- Weeks 1–2 occur before fertilization
- Ovulation usually happens around week 2
- Implantation occurs around weeks 3–4
Explore what happens in the earliest days of fetal development
First Trimester: Weeks 1–12
The first trimester is a time of rapid foundational growth. By the end of week 12, all major organ systems are formed, though development continues.
During these early weeks:
- The neural tube forms
- The heart begins beating
- Major organs start developing
- Hormone levels rise significantly
Many parents experience fatigue, nausea or morning sickness, breast tenderness, and increased urination.
Weeks 1–2
Week 3
Week 4
Week 5
Week 6
Week 7
Week 8
Week 9
Week 10 ·
Week 11
Week 12
Second Trimester: Weeks 13–27
The second trimester often brings renewed energy and visible physical changes. Fetal movement becomes noticeable, bones harden, hearing develops, facial features become more defined, and the belly begins to show.
Week 13
Week 14
Week 15
Week 16
Week 17
Week 18
Week 19
Week 20
Week 21
Week 22
Week 23
Week 24
Week 25
Week 26
Week 27
Explore detailed second trimester development milestones
Third Trimester: Weeks 28–40
The third trimester focuses on growth, maturation, and preparation for birth. Brain development accelerates, lungs mature, body fat increases, sleep cycles develop, and your baby moves into birth position.
Week 28
Week 29
Week 30
Week 31
Week 32
Week 33
Week 34
Week 35
Week 36
Week 37
Week 38
Week 39
Week 40
Explore detailed third trimester development milestones
What Changes in Your Body Week by Week
As your baby grows, your body adapts. Changes may include weight gain, skin changes, back discomfort, Braxton Hicks contractions, and disrupted sleep. Staying informed can help you feel prepared for each stage.
Get guidance on nutrition and health habits throughout every trimester
Staying Connected Throughout Pregnancy
Following pregnancy week by week can make the experience feel more tangible. Each milestone — from early heartbeats to first kicks — reflects steady progress. Pregnancy unfolds one week at a time, and each week brings you closer to meeting your baby.
Prepare for labor and birth when you are ready for the next stage
