A big milestone: starting this week, the embryo is officially called a fetus. All the essential organs have begun forming, and the rest of pregnancy is about growth, maturation, and refinement. The tail is gone, and the fetus looks increasingly human. Use our Due Date Calculator to find your estimated delivery date.
Key Takeaways
- From week 9 onward, the developing baby is officially called a fetus — all major organ systems have been established during the embryonic period (weeks 3 to 8).
- The fetus is about 23 mm (cherry size), weighs around 2 grams, and can make small, jerky movements.
- The heart now has four fully formed chambers and is beating strongly.
- First-trimester screening (nuchal translucency ultrasound + blood test) is offered between weeks 11 and 14 and screens for chromosomal conditions like Down syndrome.
Your Baby This Week
Size: Cherry (about 23 mm, or just under 1 inch)
Weight: About 2 grams
- Muscles: Forming throughout the body. The fetus can make small, jerky movements.
- Bones: Cartilage is starting to harden into bone in some areas
- Heart: Four chambers are fully formed and beating strongly
- Face: Eyes are fully formed but fused shut. Earlobes are visible.
- Fingers and toes: Separated and distinct. Touch pads are developing on the fingertips.
- Reproductive organs: Internal development continues, though sex determination on ultrasound is still weeks away
Track your baby's growth with our Milestone Tracker.
Your Body
- Nausea still going strong for many, but relief is on the horizon
- Waistline thickening: Clothes may feel snug, even though a visible bump is still weeks away
- Emotional changes: Mood swings, irritability, or unexpected tearfulness are common
- Nasal congestion: Increased blood volume can cause stuffiness, called pregnancy rhinitis
- Visible veins: Blue veins may become more prominent on your breasts and abdomen
What to Do This Week
- Learn about first-trimester screening. Between weeks 11 and 14, you may be offered a nuchal translucency ultrasound and blood test to screen for chromosomal conditions like Down syndrome.
- Look into NIPT. Non-invasive prenatal testing (a simple blood draw) can screen for chromosomal abnormalities as early as week 10 with high accuracy.
- Move your body. Even a 20-minute walk daily supports circulation, mood, and sleep. Our exercise during pregnancy guide covers safe workouts for every trimester.
Common Questions
What is the difference between an embryo and a fetus?
The embryonic period (weeks 3 to 8) is when all major organ systems are established. From week 9 onward, the developing baby is called a fetus, and the focus shifts to growth and maturation of those existing structures.
Is it normal to not "feel" pregnant?
Absolutely. Symptoms fluctuate throughout pregnancy. Some weeks you may feel very pregnant, and others you may forget entirely. Both are normal.
Frequently Asked Questions
What is the difference between an embryo and a fetus?
The embryonic period spans weeks 3 to 8, during which all major organ systems are established from scratch. From week 9 onward, the developing baby is called a fetus — the organs exist and the focus shifts to growth, maturation, and refinement of existing structures.
What is NIPT, and when can I get it?
NIPT (Non-Invasive Prenatal Testing) is a blood test that analyzes fragments of fetal DNA in the parent's bloodstream. It can screen for chromosomal conditions like Down syndrome (trisomy 21), Edwards syndrome (trisomy 18), and Patau syndrome (trisomy 13). ACOG recommends offering NIPT to all pregnant patients; it is available as early as week 10.
Is it normal to have mood swings at 9 weeks?
Yes. Hormonal changes — particularly rising levels of estrogen and progesterone — affect brain chemistry and can cause irritability, tearfulness, or unexpected emotional responses. Mood swings are very common in the first trimester and typically stabilize as hormone levels even out.
Can I find out the baby's sex at 9 weeks?
Not reliably via ultrasound yet — the external genitalia are not distinguishable until around weeks 16 to 20. However, NIPT (available from week 10) can reveal chromosomal sex (XX or XY) with high accuracy if you choose to know.
Related Articles
- Pregnancy Week-by-Week Overview — see the full timeline
- Pregnancy Week 10: Fingers, Toes, and Teeth — what comes next
- Exercise During Pregnancy, safe workouts for every trimester
Sources
🔧 Helpful Tools
- Due Date Calculator — Calculate your estimated due date
- Contraction Timer — Track your contractions during labor
- All Baby Tools — Browse all free tools for pregnancy and baby care
