Week 23: Lung Maturation Begins

An important milestone this week — the lungs begin producing surfactant! This substance is absolutely essential for your baby to be able to breathe independently after birth. The brain is growing enormously fast, and your baby can now hear your voice clearly. Talk to your bump — your baby is listening!

Your baby now weighs around 500 grams — half a kilogram! That is a symbolic milestone. Length is approximately 29 cm from head to heel. The skin is gradually thickening, but is still transparent enough that the blood vessels underneath are visible.

Baby's Development

Size and Growth

• Length: About 29 cm from head to heel
• Weight: About 500 grams (half a kilogram!)
• Comparison: The size of a large mango

Key Developmental Milestones

• Surfactant production starts: The lungs begin producing surfactant, a substance that prevents the air sacs from collapsing when the baby exhales
• Blood vessels in the lungs: The network of blood vessels is developing and preparing to absorb oxygen
• Hearing established: Your baby hears voices, music, and sounds. Many babies react with movements to loud sounds
• Rapid brain development: The brain is forming millions of new nerve connections every day
• Skin thickening: Gradually less transparent as more layers form
• Movements: The baby is very active — up to 50 movements per hour during active periods
• Blood cell production: The bone marrow is gradually taking over production from the liver

Surfactant — Life-Essential for Breathing

Surfactant is a mixture of fat and proteins that lines the inside of the air sacs (alveoli):

What surfactant does:

• Prevents the air sacs from collapsing when exhaling
• Reduces surface tension in the lungs
• Makes it possible to breathe with minimal effort
• Protects the lungs from infections

Timeline for lung maturation:

If a baby is born prematurely, doctors can administer artificial surfactant through a tube in the airway.

Hearing Develops

Your baby now hears sound waves transmitted through amniotic fluid, tissue, and bone.

Sounds your baby hears best:

• Your voice (transmitted through your body and through the air)
• Your heartbeat
• Digestive sounds
• Deep, low voices
• Music with a clear rhythm

Sounds that are more muffled:

• High-pitched voices
• Conversations in the room
• TV and radio

Research shows that newborns prefer voices and music they heard regularly during pregnancy.

Your Body

Common Symptoms

• Swollen feet: Swelling in the feet and ankles is very common due to increased blood volume
• Braxton Hicks: Practice contractions may become more noticeable
• Snoring: Swollen mucous membranes in the nose (pregnancy rhinitis) can cause snoring
• Shortness of breath: The uterus is pushing the diaphragm upward
• Pelvic pain: Relaxin and increased weight cause pain in the pelvis and hips
• Carpal tunnel syndrome: Swelling in the wrists can cause tingling or numbness in the hands

Swollen Feet — Causes and Remedies

Swelling in the feet and ankles affects many pregnant women, especially in the second half of pregnancy.

Causes:

• The body is retaining more fluid (increased blood volume)
• The uterus puts pressure on blood vessels in the pelvis
• Gravity causes fluid to pool in the legs
• Warm days worsen the swelling

Tips that help:

• Elevate your legs above heart level when resting
• Avoid standing still for long periods
• Take short walks to keep circulation going
• Drink plenty of water (dehydration makes swelling worse)
• Compression stockings provide good support
• Avoid sitting with your legs crossed
• Lie on your left side at night

According to the NHS and ACOG, mild swelling is normal. But sudden severe swelling in the face and hands can be a sign of preeclampsia and should be checked immediately.

Pregnancy Rhinitis

A blocked nose and snoring affects up to 30 percent of all pregnant women.

Causes:

• Hormones cause mucous membranes in the nose to swell
• Increased blood volume gives more blood flow through the nose

Measures:

• Saline nasal spray is safe and can provide relief
• Sleep with your upper body elevated
• Use an extra pillow under your head
• Avoid nasal sprays with decongestants (ask your doctor)
• The condition resolves after birth

Good to Know

Braxton Hicks or Real Labor?

It is important to know the difference:

If you are unsure, contact your midwife or labor and delivery unit — they are there to help you assess.

Iron and Brain Development

Now that the brain is growing quickly, iron is especially important.

Recommended intake (WHO/AAP):

• Pregnant women generally need about 27 mg of iron daily
• Supplements may be recommended if ferritin levels are low
• Ferritin can be checked with a blood test at your prenatal checkup

Good iron sources:

• Red meat (best absorption)
• Lentils and beans
• Spinach and kale
• Whole grain bread
• Iron-fortified cereals

For better absorption:

• Combine with vitamin C (bell pepper, broccoli, orange)
• Avoid taking iron with milk, coffee, or tea (these inhibit absorption)

Exercise at Week 23

WHO and ACOG recommend at least 150 minutes of moderate activity per week during pregnancy.

Especially beneficial at week 23:

• Swimming: Water supports your body wonderfully and reduces swelling
• Walking: 20–30 minutes daily keeps circulation going
• Prenatal yoga: Gently strengthens and stretches
• Prenatal exercise classes: Workouts adapted for your level and trimester

Benefits of exercising now:

• Better sleep and more energy
• Reduces back pain and swelling
• Helps prevent gestational diabetes
• Prepares your body for birth
• Improves mood

Listen to your body and take breaks when you need them.

For Your Partner

• Offer a foot massage in the evening — it eases swollen feet
• Read aloud or play music near the bump — the baby can recognize voices after birth
• Help with comfortable sleeping positions
• Join exercise activities together — a shared walk is good for both of you
• Prepare for the next prenatal checkup together (typically around week 24)

Tips for Week 23

1. Elevate your legs: Lie with your feet up 15–20 minutes, ideally above heart level
2. Good shoes: Choose roomy, supportive shoes — your feet may grow during pregnancy
3. Talk and sing: Your baby will recognize your voice after birth
4. Compression stockings: Consider support stockings if you spend long hours standing
5. Iron-rich food: Red meat, lentils, and whole grains combined with vitamin C
6. Saline spray: Try saline nasal spray for a blocked nose and snoring
7. Pelvic floor exercises: Continue with daily exercises

When to Contact a Doctor

Contact your doctor or midwife if you experience:

• Regular, painful contractions that do not ease
• Sudden severe swelling in the face or hands (possible preeclampsia)
• Pressure or heaviness in the pelvis that does not go away
• Bleeding or watery discharge from the vagina
• Constant headache with vision disturbances
• Numbness in the hands that does not ease

Did You Know?

• Surfactant saves lives: Without surfactant, the air sacs would collapse like an empty balloon with every exhale. Production starts now, but the lungs are not fully mature until around week 34–36.
• The brain is a supercomputer: Your baby's brain is forming millions of new nerve connections every day. By birth, the brain will have over 100 billion nerve cells — as many as stars in the Milky Way!
• Your baby hears you: The baby can hear the difference between voices, music, and sounds. Research shows that newborns respond more strongly to music and voices they heard in the womb.
• Feet grow: Feet can grow half to a full shoe size during pregnancy. The hormone relaxin loosens ligaments, and increased fluid makes the feet wider. For some, the change is permanent.
• The half-kilogram milestone: Your baby passes 500 grams this week! Weight will more than sextuple over the next 17 weeks.

Common Questions About Week 23

Is swelling in the feet dangerous?

A little swelling in the feet and ankles is normal. However, sudden severe swelling in the face and hands should be checked by a doctor immediately — it can be a sign of preeclampsia (pregnancy-induced hypertension).

Can the baby really hear music already?

Yes! Hearing is well developed at week 23. Your voice is heard best because it is transmitted both through the air and through your body. Try singing a particular song regularly — the baby may recognize it after birth.

Why am I suddenly snoring?

Pregnancy rhinitis affects up to 30 percent of all pregnant women. Hormones cause the mucous membranes in the nose to swell. Saline spray and sleeping with your upper body elevated can help. The condition resolves after birth.

What is the difference between Braxton Hicks and real labor?

Braxton Hicks are irregular, short, and painless. Real contractions come regularly and get stronger. If you are unsure, contact your midwife or call your labor and delivery unit to have them assess the contractions.

Should I start a birth preparation class now?

It is a bit early for most classes (which typically start at week 28–32), but a good time to look into what is available and sign up. Many classes fill up quickly.

What can I do about tingling in my hands?

Carpal tunnel syndrome is common during pregnancy. Keep your hands elevated when you sleep, avoid repetitive movements, and talk to your midwife about a wrist splint.

Next week: A big milestone — your baby reaches the threshold of viability outside the womb!