Week 27: Third Trimester Approaching
Last week of the second trimester! Your baby is sleeping and waking at regular intervals, may suck their fingers, and their lungs continue to mature.
Medically reviewed by Samantha L. Fox, RN, BSN, MSN
Nursing Informaticist · United States Navy Nurse Corps · Last reviewed
Your baby is the size of a...
🥔 Rutabaga!
👶 Baby Development
- ✓Regular sleep-wake cycles are established
- ✓Baby sucks their thumb and fingers
- ✓Lungs continue maturing
- ✓Brain is very active — forming more neural connections
- ✓Can hiccup — you might feel rhythmic movements
- ✓Baby can recognize your voice and your partner's voice
💊 Common Symptoms
- •Swelling in hands, feet, and face
- •Restless leg syndrome
- •Brain fog and forgetfulness ('mommy brain')
- •Itchy belly as skin stretches
- •Shortness of breath
- •Increased Braxton Hicks
🩺Clinical Context — From a Nurse's View
Last week of the second trimester. Tdap vaccine is recommended between 27 and 36 weeks, optimally early in this window, to maximize transfer of pertussis antibodies across the placenta to the baby (ACOG 2017). Pertussis (whooping cough) is potentially fatal to newborns who can't be vaccinated until 2 months — your immunity buys them their first 8 weeks. Get it. Same time frame: if you're Rh-negative and your antibody screen is still negative, you'll get RhoGAM (anti-D immunoglobulin) at 28 weeks to prevent isoimmunization. If you have any bleeding before then, that earns RhoGAM sooner. Sleep is getting harder — left-side sleeping is technically optimal in the third trimester to maximize blood return, but the difference between left and right is small in healthy pregnancies; what matters is not back-sleeping for long stretches. A pregnancy pillow between the knees and behind the back helps.
Written by Samantha L. Fox, RN, BSN, MSN — Emergency Department nurse, US Navy Nurse Corps officer.
🚨 When to Call (or Go to the ER)
- !Severe headache, vision changes, RUQ pain, swelling — call (preeclampsia)
- !Decreased fetal movement — call
- !Regular contractions, fluid leak, bleeding — call
✅ Normal — Even If It Feels Worrying
- ✓Swelling that comes on by evening and resolves overnight
- ✓Brain fog and forgetfulness
- ✓Itchy stretching belly
- ✓Insomnia from positioning and bathroom trips
✅ To-Do This Week
- Get the Tdap vaccine (whooping cough protection for baby)
- If Rh-negative, get the RhoGAM shot
- Start buying postpartum recovery supplies
- Attend childbirth preparation classes
- Discuss cord clamping preferences with your doctor
- Prepare for the third trimester — the home stretch!
🩺 Questions for Your Doctor
- ?When should I get the Tdap vaccine?
- ?Do I need the RhoGAM injection?
- ?Is the baby in a good position?
- ?How is my weight gain overall?
- ?Should I be doing anything to prepare for preterm labor?
- ?What changes should I expect in the third trimester?
📚 References
- [1]ACOG Committee Opinion No. 718: Update on Immunization and Pregnancy: Tetanus, Diphtheria, and Pertussis Vaccination. Obstet Gynecol. 2017;130(3):e153-e157.
- [2]ACOG Practice Bulletin No. 222: Gestational Hypertension and Preeclampsia. Obstet Gynecol. 2020;135(6):e237-e260.
Editorial review: Samantha L. Fox, RN, BSN, MSN. Last reviewed: see footer.
Your baby is the size of a...