Week 23
Your baby is the size of a grapefruit
At 23 weeks, your baby is grapefruit-sized, about a pound, and roughly 11 inches head to heel. Per Mayo Clinic, two big things start this week. The lungs begin making surfactant, and ridges form in the palms and soles that will become fingerprints and footprints. Meanwhile, your memory feels like a sieve. The science says you're not imagining it.
Key takeaways
- Your baby's lungs are starting to make surfactant, the slippery coating that keeps air sacs from collapsing. Mayo Clinic flags week 23 as when this begins. Full maturity comes much later.
- ACOG recommends resuscitation begin at 24 weeks, with consideration at 22 and 23 weeks. Per the ACOG/SMFM Periviable Birth consensus, survival to hospital discharge at 23 weeks is roughly 23% to 27%.
- Pregnancy brain is real. A 2025 BMC Pregnancy and Childbirth systematic review found measurable dips in working memory and processing speed in the second and third trimesters.
- Ridges are forming in your baby's palms and soles that will become the fingerprints and footprints they have for life, per Mayo Clinic.
Why the lungs your baby is building this week determine how a 23-week birth ends
At 23 weeks, your baby is grapefruit-sized, about a pound, and roughly 11 inches head to heel per Cleveland Clinic. Per Mayo Clinic, the lungs are starting to make surfactant this week, the slippery coating that lines the air sacs and keeps them from collapsing on exhalation. It's what your baby will need to breathe room air after birth. Production keeps ramping up and isn't fully mature until close to term.
This is also why week 23 sits inside the medical category called periviability.
Per ACOG, resuscitation is recommended starting at 24 weeks, with consideration at 22 and 23 weeks. The ACOG/SMFM Obstetric Care Consensus on Periviable Birth gives the survival-to-discharge range at 23 weeks as roughly 23% to 27%, climbing to 42% to 59% at 24 weeks and 67% to 76% at 25 weeks. Every additional week in the womb shifts those numbers a lot.
Mayo also notes that rapid eye movements are starting now, and ridges are forming in the palms and soles, the foundation of fingerprints and footprints. Those patterns are already unique. Already permanent.
None of this is meant to alarm you. The vast majority of pregnancies continue normally to term. It's meant to put the week in honest perspective. Your baby is real, working, and getting closer to the version you'll meet.
What pregnancy brain actually does, and the one move that helps more than willpower
You're not making it up.
The conventional joke is that pregnancy brain is hormones plus tiredness. Both real, both rough. The actual neuroscience is more specific. A 2025 systematic review in BMC Pregnancy and Childbirth (Younis et al.) found measurable dips in executive function, memory, and processing speed during pregnancy, with the biggest drops in the second and third trimesters. A 2024 brain-imaging study (Pritschet et al.) saw matching reductions in cortical volume in the regions that handle those tasks.
It's neurobiology, not character.
And it doesn't last.
What actually helps right now:
- Externalize as much as possible. A list in your phone, sticky notes on the door, a shared family calendar. Anything that gets the load out of your head.
- One inbox for to-dos. Single notebook or app. Not five running lists.
- Lower the bar. This is a season, not a personality.
Meanwhile, your skin is stretching faster than it's used to and your center of gravity has shifted forward. Daily belly moisturizer won't prevent stretch marks but does ease the itch. A wedge tucked under the bump or behind the lower back makes side-sleeping easier than wrestling a U-pillow all night. Daily walks and gentle pelvic mobility take some of the back-pain edge off.
Contact your provider right away if you have regular contractions that don't go away, a watery or bloody discharge, persistent low-back pain that comes and goes, or pelvic pressure. At 23 weeks, those can point to preterm labor and need same-day evaluation.
For dads
Here's your move:
At 23 weeks, your baby's lungs are starting the work that will let them take a first breath. That fact will hit your partner this week and tilt the abstract toward real. Use the moment. Pick one big decision you've been putting off and finish it. Pediatrician. Daycare waitlist. Stroller. Any one of those. The choice itself matters less than the relief of a thing crossed off. While you're at it, ask her what's on her mental list that you can take. Don't guess. Ask. She'll know the specific thing that'd help.
Real talk:
Pregnancy brain is real, and it lands harder than most people admit. Your partner may have been the planner in the relationship for years and is now forgetting words mid-sentence. That's not a failure of effort. A 2025 BMC review confirmed measurable cognitive changes through the second and third trimesters. So when she asks for help remembering an appointment, the answer isn't 'I told you yesterday.' The answer is to add it to a calendar you both share. Be the redundancy in the system. The forgetting will fade. The pattern you set now is what your partnership runs on later.
Common concerns
Is it normal that I can't remember anything anymore at 23 weeks?+
Yes, and there's research to back you up. A 2025 BMC Pregnancy and Childbirth systematic review found measurable dips in working memory, executive function, and processing speed during pregnancy, biggest in the second and third trimesters. It tends to resolve postpartum, though sleep deprivation with a newborn adds a different cognitive challenge. Externalize anything important onto a list, a calendar, or your phone, and lower your expectations about how much you can keep in your head.
What happens if my baby is born this week?+
At 23 weeks, your baby is in what's called the periviable window. Per ACOG, resuscitation is recommended starting at 24 weeks with consideration at 22 and 23 weeks. The ACOG/SMFM Periviable Birth consensus gives survival to hospital discharge at 23 weeks as roughly 23% to 27%, with outcomes very dependent on individual circumstances. The vast majority of pregnancies continue normally to term, but if you have any signs of preterm labor, call your provider immediately.
Will moisturizing prevent stretch marks?+
No. Research has not shown any topical treatment reliably prevents stretch marks, and genetics largely determine who gets them. Moisturizer does help with the itch as your skin stretches, so it's worth using just for that reason.
When should I call my provider this week?+
Regular contractions that don't go away, a watery or bloody discharge, low-back pain that comes and goes, persistent pelvic pressure, or any sudden change in how you feel. At 23 weeks those can be signs of preterm labor and need same-day evaluation. Your provider would rather hear from you unnecessarily than miss an early sign.
Product picks for week 23
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Palmer's Cocoa Butter Formula Massage Lotion (8.5 oz)
Cocoa butter, collagen, elastin, and argan oil belly cream. Most-reviewed pregnancy moisturizer on Amazon.
Skechers Women's Go Walk Joy Slip-On Sneaker
Lightweight slip-on with cushioned insole for the daily walks that take the back-pain edge off.
Hiccapop Pregnancy Wedge Pillow for Belly Support
Belly wedge that makes side-sleeping easier than fighting a full U-pillow all night, exactly as section 2 recommends.
Sources
- Mayo Clinic, Fetal Development: The 2nd Trimester (2025) — https://www.mayoclinic.org/healthy-lifestyle/pregnancy-week-by-week/in-depth/fetal-development/art-20046151
- ACOG, Facts Are Important: Understanding and Navigating Viability — https://www.acog.org/advocacy/facts-are-important/understanding-and-navigating-viability
- ACOG/SMFM Obstetric Care Consensus #6, Periviable Birth (Interim Update) — https://publications.smfm.org/publications/272-acog-smfm-obstetric-care-consensus-6-periviable-birth/
- Younis E et al., Exploring the influence of pregnancy on cognitive function in women: a systematic review, BMC Pregnancy and Childbirth (2025) — https://link.springer.com/article/10.1186/s12884-025-07181-3
- Cleveland Clinic, Fetal Development: Week-by-Week — https://my.clevelandclinic.org/health/articles/7247-fetal-development-stages-of-growth
A quick note: This content is for informational purposes only and is not a substitute for professional medical advice. Always talk to your healthcare provider about any questions or concerns. Content based on guidance from the American College of Obstetricians and Gynecologists (ACOG), the American Academy of Pediatrics (AAP), Mayo Clinic, and peer-reviewed medical literature. Learn how we create our content.