Week 28
Your baby is the size of an eggplant
Welcome to the third trimester. Per Mayo Clinic, at week 28 your baby's eyelids can partially open and the central nervous system can now control body temperature. This is also the visit where two routine shots typically arrive: anti-D immune globulin if you're Rh-negative per ACOG, plus Tdap for every pregnancy per CDC. Here's what's actually new this week, and what to expect when you walk in.
Key takeaways
- Week 28 starts the third trimester per ACOG. Eyelids can partially open this week per Mayo Clinic, and the central nervous system can now control body temperature.
- Anti-D immune globulin (RhoGAM) is offered to unsensitized Rh-negative pregnant patients at 28 weeks per ACOG. Roughly 15% of US pregnancies are Rh-negative.
- CDC recommends Tdap between 27 and 36 weeks of every pregnancy, as early in that window as possible. It prevents 78% of pertussis cases in infants younger than 2 months.
- Visits typically shift to every two weeks starting now per the traditional ACOG schedule. ACOG's 2025 tailored prenatal care guidance allows individualization for low-risk patients.
Your baby's eyes open this week, and the nervous system just took over temperature control
Per Mayo Clinic, at 28 weeks your baby's eyelids can partially open.
This is the milestone weeks 25 and 26 kept previewing.
Eyes have been structurally complete since week 26: retinas, lenses, eyebrows, and eyelashes all in place.
The lids stayed fused. They unfuse now.
By week 30 they'll open wide per Mayo Clinic. Week 33 is when pupils can change size in response to light.
Two other shifts arrive this week per Mayo Clinic:
- The central nervous system can control body temperature. That's the system that keeps a newborn warm against ambient air after birth.
- Breathing movements can be triggered by the central nervous system. They show up on ultrasound. Your baby is rehearsing the diaphragm motion for that first breath.
Crown-to-rump, your baby is around 10 inches (250 mm) and weighs about 2 1/4 pounds (1,000 g) per Mayo Clinic.
As covered at week 27, cortical gray matter is on its 4-fold ramp through the third trimester. Eyes open. Lungs rehearsing.
Why the 28-week visit feels heavier than the others
There's a reason this visit takes longer.
Shot one: anti-D immune globulin (RhoGAM). Per ACOG, anti-D is offered to unsensitized Rh-negative patients at 28 weeks. Roughly 15% of US pregnancies are Rh-negative. Before routine prophylaxis, sensitization happened in 10% to 15% of Rh-negative pregnancies delivering Rh-positive infants. The dose dropped that to about 1 per 1,000 births.
If your Rh status is positive, you skip this one.
Shot two: Tdap, for every pregnancy. Per CDC, Tdap is recommended between 27 and 36 weeks, as early as possible. It prevents 78% of pertussis cases in infants younger than 2 months. Antibodies cross the placenta and protect the baby until their own vaccine at 2 months.
Visit cadence shifts now. Traditional ACOG schedule: every two weeks until 36, then weekly. ACOG's 2025 tailored guidance allows individualization for low-risk pregnancies.
Here's the thing on movement: formal kick counting becomes the standard ask for low-risk pregnancies at 28 weeks per ACOG. Ten movements in two hours during your baby's active stretch. A simple printed kick chart on the fridge or a movement-tracking journal makes the daily count easier to share with your provider.
Contact your provider right away if you have a sustained drop in movement, regular contractions, fluid leakage, heavy bleeding, severe headache with vision changes, sudden swelling in the face or hands, or upper-belly pain.
For dads
Here's your move:
Block her calendar for the next 12 weeks. Visits move to every two weeks now, then weekly at 36 per the traditional ACOG schedule. A paper pregnancy planner works because she can keep notes from each visit in one place. The third trimester stacks up practical decisions: pediatrician, hospital tour, leave timing, who's in the delivery room. Book your Tdap if it's been over 10 years. CDC recommends it for close adult contacts at least two weeks before birth, grandparents included. If you haven't grabbed a pregnancy book yet, week 28 is the fair deadline. And install the car seat this weekend at a free local fire-department inspection.
Real talk:
Twelve weeks sounds like a lot. Then it isn't. The third trimester compresses time in a way the second never did. Her sleep is unlikely to get easier from here. If she hasn't tried a pregnancy support pillow or wedge, this is the week. Yours will too. You'll start sleeping lighter, waking up to refresh the contraction-tracker app. That's normal. What helps her most is not pretending the discomfort is small. Don't try to silver-lining the heartburn or back pain. 'That sounds miserable, I'm sorry' is a complete answer. So is doing the dishes without being asked. The unglamorous showing-up over the next 12 weeks is the work.
Common concerns
Why is the 28-week appointment so much longer than the others?+
Because this is the visit that bundles bloodwork, the anti-D injection if you're Rh-negative per ACOG, and the Tdap per CDC. Some practices also do a complete blood count and finish the gestational diabetes screen if it wasn't done at 26. It's a heavy visit.
Should my partner get Tdap too?+
Yes, per CDC. Adults in close contact with a newborn (partners, grandparents, older siblings, regular caregivers) should be up to date on Tdap, ideally at least two weeks before they meet the baby. Pertussis spreads from adults who don't know they have it, and newborns can't get their own vaccine until 2 months.
Do I still need RhoGAM if my partner is also Rh-negative?+
If your partner is confirmed Rh-negative, your baby will be Rh-negative too and anti-D isn't strictly necessary. In practice, providers typically still give the 28-week dose unless paternal Rh status is certain (which usually requires testing). Talk to your provider about whether to skip it. The dose itself is safe either way.
My baby is moving less today. Is that an emergency?+
Not necessarily. Babies have quieter stretches, especially when you're moving (the motion rocks them to sleep) or right after a meal. Try the reset: something cold or sweet to drink, lie on your side, count for two hours in your baby's typically active window. If you don't reach 10 movements or the drop feels significant compared to the normal pattern, call your provider. Don't wait until morning.
Product picks for week 28
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What to Expect When You're Expecting (Updated 2025)
The both-parents reference the third trimester actually rewards. Newly updated 2025 edition with over 30,000 reviews.
Hiccapop Pregnancy Pillow Wedge for Belly Support
Wedge under the belly or behind the back. Targeted support for the side-sleep position that gets harder as the bump moves forward in the third trimester.
Momcozy Pregnancy Pillows for Sleeping, U Shaped Full Body Maternity Pillow, 57 Inch
Full-body U-shape with the deepest review base in the category. Replaces the back-leg-belly setup that gets fragile in the third trimester.
Sources
- Mayo Clinic, Fetal Development: The 3rd Trimester (March 2025) — https://www.mayoclinic.org/healthy-lifestyle/pregnancy-week-by-week/in-depth/fetal-development/art-20045997
- ACOG, Management of Alloimmunization During Pregnancy (Practice Bulletin) — https://www.acog.org/clinical/clinical-guidance/practice-bulletin/articles/2018/03/management-of-alloimmunization-during-pregnancy
- CDC, Tdap Vaccination for Pregnant Women — https://www.cdc.gov/pertussis/vaccines/tdap-vaccination-during-pregnancy.html
- ACOG, Tailored Prenatal Care Delivery for Pregnant Individuals (Clinical Consensus, April 2025) — https://www.acog.org/clinical/clinical-guidance/clinical-consensus/articles/2025/04/tailored-prenatal-care-delivery-for-pregnant-individuals
- Andescavage NN et al., Complex Trajectories of Brain Development in the Healthy Human Fetus. Cerebral Cortex (2017) — https://academic.oup.com/cercor/article/27/11/5274/2354954
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.