Baby Care Guide ↗
Evidence-based. References guidelines from ACOG, CDC, and WHO.
Informational only, not medical advice. Always consult your OB/GYN or healthcare provider.
Week 20 is a major milestone — you’re officially halfway through pregnancy. Most people feel relatively good in the second trimester, baby’s movements are becoming clearer, and the anatomy scan (also called the level 2 ultrasound) gives you the most detailed look at your baby yet.
Here’s what’s happening at 20 weeks pregnant: your baby’s growth, the symptoms you’re likely feeling, what to expect at the anatomy scan, and what’s coming next.
📌 Key Takeaway: According to March of Dimes data, about 10% of US babies are born preterm (before 37 weeks), making week-by-week monitoring important. This guide gives you evidence-based, practical guidance you can apply today. For a related deep dive, see our guide on 20 week ultrasound.
Baby’s Size at 20 Weeks Pregnant
At 20 weeks, your baby is roughly the size of a banana — about 6.5 inches (16.5 cm) crown-to-rump (or about 10 inches head-to-heel) and weighing around 10.5 oz (300 g).
| Measurement | Week 20 |
|---|---|
| Length (crown-heel) | 25 cm (10 in) |
| Weight | 300 g (10.5 oz) |
| Comparable to | Banana |
| Amniotic fluid | ~320 ml |
Note: Around now, doctors switch from measuring crown-to-rump to head-to-heel because baby’s legs are extended.
What’s Developing This Week
- Skin is developing layers, including a waxy coating called vernix caseosa that protects skin in amniotic fluid
- A fine downy hair called lanugo covers the body
- Hearing is functioning — baby can hear your voice, heartbeat, and digestion
- Taste buds are forming and baby can detect flavors in the amniotic fluid
- Gender-distinct genitals are clearly visible on ultrasound
- Brain regions for hearing, sight, taste, smell, and touch are developing
- Baby has regular sleep-wake cycles of about 20 minutes each
Symptoms This Week
The second trimester is often the most comfortable phase, but new symptoms appear as your bump grows.
Common Week 20 Symptoms
- Fetal movement (quickening) — flutters or “popcorn” sensations, becoming more defined
- Visible bump — your uterus reaches your belly button by 20 weeks
- Round ligament pain — sharp pulls on either side of the lower belly when you stand or twist
- Backache as posture shifts
- Leg cramps (often at night)
- Heartburn as the uterus presses upward
- Increased appetite and clearer cravings
- Stretch marks beginning to appear
- Linea nigra (dark line down the belly) and skin pigmentation changes
- Nasal congestion (“pregnancy rhinitis”)
- Mild swelling in feet and ankles
When to Call Your Provider
- Severe abdominal pain
- Heavy bleeding
- Persistent headaches with vision changes
- Sudden severe swelling in face or hands
- Fewer than expected movements once you’re feeling them daily
What to Do This Week
Attend the Anatomy Scan
The 20-week anatomy scan is the most thorough ultrasound of pregnancy. It typically takes 30–60 minutes and checks:
- All four heart chambers and major blood vessels
- Brain structures
- Spine (looking for spina bifida)
- Stomach, kidneys, and bladder
- Arms, legs, fingers, toes
- Placenta location
- Amniotic fluid level
- Cervical length
- Baby’s growth/measurements
- Sex (if you want to know)
For a deep dive, read our complete 20-week ultrasound guide.
Start Thinking About Baby Logistics
Halfway is a great time to:
- Book a childbirth class (many fill 8–12 weeks ahead)
- Plan your registry
- Tour hospitals or birth centers
- Discuss parental leave with HR
- Start considering pediatricians
Track Movements (Loosely for Now)
You don’t need formal kick counts yet, but you’ll start noticing patterns. Formal counting starts around 28 weeks.
Sleep on Your Side
After 20 weeks, ACOG recommends side-sleeping (left side ideal) to maximize blood flow. Use a pregnancy pillow if helpful — see our sleeping positions guide.
Doctor Visit at Week 20
Most people have a routine prenatal at 20 weeks plus the separate anatomy scan.
| Test or Activity | Purpose |
|---|---|
| Weight, blood pressure, urine | Routine screening |
| Fundal height measurement | Track uterine growth |
| Heartbeat | Confirm fetal well-being |
| Anatomy ultrasound | Detailed fetal assessment |
| Discussion of glucose screening | Plan for ~24-week test |
Looking Ahead: Weeks 20 to 28
The second half of the second trimester brings:
- Week 24: Viability milestone in many hospitals
- Week 24–28: Glucose screening for gestational diabetes
- Week 28: Tdap vaccine and possibly Rh immune globulin if you’re Rh-negative
- Strong, regular movements that partners can feel from the outside
For the full roadmap, see our pregnancy week-by-week guide.
Frequently Asked Questions
What if the anatomy scan finds something abnormal?
Most scans are reassuringly normal. If something is flagged, your provider will discuss next steps — often a follow-up scan, referral to maternal-fetal medicine, or additional testing. A “soft marker” alone often turns out to be nothing.
Can I tell the baby’s sex at 20 weeks?
Yes, with high reliability — usually 95–99% accurate. NIPT (a blood test from 10 weeks) is even more accurate if you wanted to know earlier.
Why does the bump look so different from other 20-weekers online?
Bump size and shape depend on body type, abdominal muscles, baby’s position, whether it’s your first pregnancy, and even the time of day. There’s a huge range of normal.
Is it safe to feel the baby move sometimes but not always?
At 20 weeks, movements are still subtle and irregular. Many people feel them more in quiet moments. Daily counting starts later (~28 weeks). Mention to your OB if you’re not feeling any movement.
Should I be sleeping only on my left side?
Left-side sleeping is ideal but right side is also fine. The main goal is to avoid lying flat on your back for long periods after 20 weeks. If you wake on your back, just roll to a side.
💡 Related Resources: After baby arrives, visit our sister site baby.chparenting.com for newborn care, sleep training, feeding guides, and developmental milestones.
References
- ACOG — Ultrasound Exams
- Mayo Clinic — 2nd Trimester Pregnancy
- NIH MedlinePlus — Fetal Development
- CDC — Pregnancy Health
- ACOG — Exercise During Pregnancy
Medical Disclaimer: This article is for educational purposes only and is not a substitute for professional medical advice. Talk to your OB/GYN about your specific scan results and pregnancy.
Written by
Vega LinFounder & Editor — Mother of 2 (Taiwan)
Vega writes Pregnancy Guide from the intersection of evidence-based research (ACOG, CDC, WHO) and her own experience as a mother of two. Completing her Master's in Digital Innovation at Tunghai University. Read more →
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