A beautiful milestone: the fetus can now hear sounds from the outside world. Your voice, music, and even loud noises can reach the baby through the amniotic fluid. The anatomy scan is typically scheduled around now, giving you a detailed look at your growing baby. Use our Due Date Calculator to track your timeline.
Key Takeaways
- At 18 weeks, your baby is about 14 cm long (the size of a sweet potato) and weighs roughly 190 grams
- The auditory system is functional — the fetus can hear external sounds and may startle at sudden loud noises
- Myelin (a protective nerve coating) is starting to form, which speeds up brain signal transmission
- The fetus is developing sleep-wake cycles, though they do not match yours
- The anatomy scan (weeks 18–22) checks the baby's brain, heart, spine, organs, and often the sex
Your Baby This Week
Size: Sweet potato (about 14 cm, or 5.6 inches)
Weight: About 190 grams
- Hearing: The ears are now positioned on the sides of the head (having migrated from the neck), and the auditory system is functional enough to pick up sounds. Sudden loud noises may cause the fetus to startle.
- Nervous system: Myelin, a protective coating, is starting to form around nerves. This speeds up signal transmission.
- Yawning: The fetus yawns frequently, which may help regulate brain temperature and blood flow
- Genitals: Usually identifiable on ultrasound now
- Sleep cycles: The fetus starts to develop patterns of sleeping and waking, though they do not match yours
Track your baby's growth with our Milestone Tracker.
Your Body
- Feeling the baby move. By week 18, many people feel definite movements. These may still be subtle, like tapping or popping.
- Growing belly. Your uterus is approximately at the level of your navel.
- Lower blood pressure in mid-pregnancy is normal and may cause lightheadedness.
- Leg cramps, especially at night, may start occurring.
- Swelling in the feet and ankles, particularly at the end of the day.
What to Do This Week
- Prepare for the anatomy scan. This detailed ultrasound during pregnancy (usually between weeks 18 and 22) checks the baby's organs, spine, limbs, brain, heart, and placenta position. It typically takes 30 to 45 minutes.
- Decide if you want to know the sex. Tell the sonographer at the start of the appointment. If you want it to be a surprise, make sure they know.
- Stretch before bed to help prevent leg cramps. Staying hydrated and getting enough magnesium (from nuts, seeds, and dark chocolate) can also help.
Common Questions
What does the anatomy scan check?
The mid-pregnancy ultrasound (also called the structural or morphology scan) examines the baby's brain, face, spine, heart, stomach, kidneys, bladder, limbs, and placenta. It also checks amniotic fluid levels and can often determine the sex. If anything looks unusual, your provider will explain the next steps.
Can the baby hear music?
Yes. Research shows that fetuses respond to music by changing their heart rate or moving. Some studies suggest babies may recognize music they heard frequently in the womb after they are born. Playing music or talking to your baby is a lovely bonding activity.
FAQ
Can the baby really hear me at 18 weeks?
Yes. By week 18, the auditory system is developed enough to detect sounds from outside the womb. The fetus hears sounds transmitted through the amniotic fluid — your voice, heartbeat, and external noises. Research shows that newborns recognize and prefer their mother's voice, which they have heard throughout pregnancy.
What does the anatomy scan check at 18 weeks?
The mid-pregnancy anatomy scan (also called the structural scan or morphology scan) is a comprehensive ultrasound that examines the baby's brain, face, spine, heart, lungs, stomach, kidneys, bladder, limbs, and placenta position. It also checks amniotic fluid levels. It typically takes 30 to 45 minutes.
What causes leg cramps during pregnancy?
Leg cramps — especially at night — are very common in the second trimester. They may be related to changes in circulation, pressure on nerves from the growing uterus, or low levels of magnesium, calcium, or potassium. Stretching before bed, staying well hydrated, and eating magnesium-rich foods (nuts, seeds, dark chocolate) can help.
Is swelling in the feet normal at 18 weeks?
Mild swelling in the feet and ankles (edema) is common and normal during pregnancy, especially by the end of the day. It occurs because increased blood volume and pressure from the uterus slow circulation in the legs. Elevating your feet, avoiding prolonged standing, and wearing supportive footwear all help. Contact your provider if swelling is sudden, severe, or accompanied by headaches or vision changes.
Should I feel my baby moving every day at 18 weeks?
Not necessarily. While many people begin to feel movement between weeks 16 and 22, daily consistent kicks are not expected until around week 28, when formal kick counting is typically recommended. At 18 weeks, movements may still be intermittent and subtle.
Related Articles
- Pregnancy Week-by-Week Overview — see the full timeline
- Pregnancy Week 19: Vernix and Senses — what comes next
- Ultrasound During Pregnancy, what to expect at your scans
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
