5 Weeks Pregnant
You’re 5 weeks pregnant — in the first trimester, and 35 weeks to go until your due date. Your baby is about the size of a sesame seed this week.
★ The neural tube and early heart begin to form.
How big is your baby at 5 weeks?
Size of a
sesame seed
Length
~0.3 cm
Weight
—
Last week your baby was about the size of a poppy seed; this week it's grown to roughly a sesame seed.
Sizes are averages from standard fetal-growth references. Every baby grows at its own pace — your provider tracks yours at scans.
Baby development at week 5
The embryo's major systems start forming. The neural tube — which becomes the brain and spinal cord — begins to develop, and a tiny heart tube starts to form and will soon begin to beat. Three layers of cells are now differentiating into everything from the nervous system to the digestive tract. At about the size of a sesame seed, growth this week is rapid and foundational.
Your body at 5 weeks
Common symptoms many people notice around week 5 include:
- Rising fatigue as hormone levels climb
- Nausea may begin ('morning' sickness can strike any time)
- Frequent urination
- Heightened sense of smell and food aversions
Symptoms vary enormously from person to person and pregnancy to pregnancy. Not having a symptom on this list is just as normal as having it.
Tips for week 5
- Folic acid matters most now — the neural tube is forming
- Eat small, frequent snacks to manage early nausea
- Rest when you can; first-trimester fatigue is real
What trimester is 5 weeks?
Week 5 falls in the first trimester. As a quick map: the first trimester runs weeks 1–13, the second covers weeks 14–27, and the third is week 28 through birth (a due date is set at 40 weeks). Want your own dates? Our Pregnancy Due Date Calculator shows your due date and exactly how far along you are today.
The first trimester (weeks 1–13) is when the baby's major organs and body systems form, and when pregnancy symptoms like nausea and fatigue are usually strongest. It's also when most prenatal care begins — the dating scan, early bloodwork, and (if you choose) genetic screening all happen in this window.
Frequently asked questions
- How many months is 5 weeks pregnant?
- 5 weeks pregnant is about 2 months. Pregnancy months don't divide evenly into 4-week blocks, so week-to-month conversions are approximate — most providers track pregnancy by week, not month.
- How big is the baby at 5 weeks?
- At 5 weeks, the baby is about the size of a sesame seed, roughly 0.3 cm. These are averages — healthy babies vary, and your provider tracks your baby's own growth curve at scans.
- What trimester is 5 weeks?
- Week 5 is in the first trimester. The first trimester is weeks 1–13, the second is weeks 14–27, and the third is weeks 28 to birth (around week 40).