23 Weeks Pregnant: Baby’s Lungs Are Developing
Medically reviewed by
Maureen Kelly, RN — 20+ years in L&D, postpartum, NICU, and women’s health.
Reviewed against ACOG, AAP, and Mayo Clinic guidance. Meet Maureen →
Medical Disclaimer: This article is for informational purposes only and should not replace professional medical advice. Always consult with your healthcare provider about your individual pregnancy.
At 23 weeks pregnant, your baby is about the size of a grapefruit—roughly 11.4 inches long and weighing just over 1 pound. Your baby’s lungs are developing surfactant, a critical substance that will help them breathe after birth. You’re likely feeling strong, regular movements and settling into the rhythm of your second trimester. The third trimester is approaching, and preparations are starting to feel more real.
Baby Development at 23 Weeks
Your baby measures about 11.4 inches and weighs approximately 1.1 pounds. The lungs are a major focus this week—they’re beginning to produce surfactant, a substance that keeps the air sacs open after birth. Without surfactant, breathing would be extremely difficult.
Your baby’s skin is still thin and wrinkled but is beginning to fill out with fat. Blood vessels in the lungs are developing to prepare for gas exchange. Your baby’s hearing continues to improve—they can now distinguish different sounds and may startle at loud noises. The brain is growing rapidly, creating billions of neural connections.
Your Body This Week
Your uterus extends about 1.5 inches above your navel. Weight gain is typically 12-18 pounds total. You may notice your feet growing—hormonal changes and weight gain can permanently increase foot size by half to a full size.
Swelling in your hands and feet may increase. Your skin may feel itchy as it stretches. If itching is severe (especially on palms and soles), mention it to your provider as it could indicate a liver condition called cholestasis.
Common Symptoms at 23 Weeks
Strong baby movements: Kicks, rolls, and stretches are becoming more powerful and regular. Partners may be able to feel them from outside.
Snoring: Nasal congestion and increased blood flow can cause snoring even if you never snored before. A humidifier may help.
Gum sensitivity: Pregnancy gingivitis causes swollen, bleeding gums. Maintain good oral hygiene and see your dentist.
Carpal tunnel symptoms: Fluid retention can compress nerves in your wrists, causing tingling, numbness, or pain in your hands.
What to Do This Week
Research childbirth classes. If you haven’t signed up, do so now. Popular classes fill up quickly, and most are attended during the third trimester.
Start planning the nursery. Research cribs (ensure they meet current safety standards), choose bedding, and consider room layout.
Prepare for the glucose screening test coming in weeks 24-28. See our gestational diabetes diet guide.
Continue exercise. Pregnancy-safe activities support your health and prepare you for labor.
Nutrition Spotlight: B Vitamins
B vitamins (B6, B12, folate, thiamine, riboflavin) support your baby’s brain development, nervous system formation, and energy metabolism. Good sources include whole grains, lean meats, eggs, legumes, leafy greens, and fortified cereals. Your prenatal vitamin provides a baseline, but dietary sources remain important. Visit our pregnancy nutrition guide.
When to Call Your Doctor
- Vaginal bleeding or fluid leaking
- Regular, painful contractions (more than 4-6 per hour)
- Severe headaches or vision changes
- Sudden severe swelling
- Severe itching, especially on palms and soles
- Decreased fetal movement
See our when to call your doctor guide.
Frequently Asked Questions
What is surfactant and why is it important?
Surfactant is a substance produced in the lungs that keeps air sacs open, enabling breathing. Without it, the lungs would collapse between breaths. Production begins around 23 weeks but doesn’t reach adequate levels until about 35 weeks.
Can my partner feel the baby kick?
By 23 weeks, kicks are often strong enough to feel from outside. Have your partner place their hand on your belly when the baby is active. It may take patience—babies sometimes stop moving when pressure is applied.
Is it normal for my feet to grow during pregnancy?
Yes. Hormonal changes (relaxin) loosen foot ligaments, and weight gain can flatten arches. Many women go up half to a full shoe size, and the change can be permanent.
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Key takeaways for the second trimester
- Energy typically returns. Many people feel their best during the second trimester.
- The anatomy scan (around weeks 18–22) is a comprehensive ultrasound that checks fetal organ development and confirms placenta position.
- Quickening — first felt fetal movement — typically begins between weeks 16 and 22, earlier in subsequent pregnancies.
- Glucose screening for gestational diabetes is usually scheduled between weeks 24 and 28.
- By 24 weeks, viability is reached with intensive NICU support; by 28 weeks, survival rates exceed 90% in well-equipped centers.
When to call your provider
Call your OB-GYN, midwife, or labor and delivery unit right away if you experience:
- Heavy vaginal bleeding (more than light spotting)
- Severe abdominal or pelvic pain
- A severe headache that doesn’t respond to acetaminophen
- Sudden facial, hand, or leg swelling
- Vision changes (spots, blurring, light sensitivity)
- Decreased fetal movement after 28 weeks (fewer than 10 movements in 2 hours during baby’s active period)
- Signs of preterm labor: regular contractions, pelvic pressure, low back pain, fluid leaking
- Fever over 100.4°F (38°C)
When in doubt, call. Your provider would always rather hear from you about a non-issue than miss something important.
Frequently asked questions about week 23
How big is the baby at 23 weeks pregnant?
At 23 weeks, your baby is roughly the size of a large mango (~11.4 inches, 1.1 lb). Size estimates vary from baby to baby and are based on standardized growth charts (ACOG, NICHD).
What symptoms are common at 23 weeks pregnant?
Common second-trimester symptoms include round ligament pain (sharp pulls in the lower belly), nasal congestion, mild leg cramps, increased appetite, and the first felt fetal movements. Many people report feeling their best in this trimester.
What prenatal appointments happen around 23 weeks?
The glucose challenge test for gestational diabetes is typically performed between weeks 24 and 28.
When should I worry at 23 weeks pregnant?
Decreased fetal movement after you have started feeling consistent kicks, severe headache, vision changes, sudden swelling, severe abdominal pain, vaginal bleeding, leaking fluid, or signs of preterm labor (regular contractions before 37 weeks) warrant immediate evaluation.
Is what I’m feeling at 23 weeks normal?
Most of the symptoms experienced at 23 weeks are part of typical pregnancy and reflect your body’s adjustments. If anything feels alarming, severe, or unusual for you, contact your provider — trust your instincts.
Sources
- American College of Obstetricians and Gynecologists (ACOG). Your Pregnancy and Childbirth: Month to Month (current edition). acog.org
- American Academy of Pediatrics. Caring for Your Baby and Young Child (current edition).
- Mayo Clinic. Pregnancy week by week. mayoclinic.org
- National Institute of Child Health and Human Development (NICHD). Pregnancy and Pregnancy Loss research and guidance.