Week 33 of Pregnancy
Learn about your baby's development and what to expect at 33 weeks pregnant.
Baby's Size This Week
Baby Development at Week 33
- ● At week 33, your baby is about 43.7 cm long and weighs around 1918g.
- ● The immune system is strengthening as your body transfers increasing amounts of antibodies across the placenta — this passive immunity protects your newborn in the first months of life.
- ● Most major organ systems are maturing; the lungs are nearly ready for independent breathing, with surfactant production at a functional level.
- ● Your baby is likely positioned head-down (vertex) and may already be engaging in the pelvis in preparation for birth.
- ● The bones of the skull remain flexible and will overlap slightly (molding) during birth to fit through the birth canal — a normal and temporary phenomenon.
- ● Rapid weight gain continues — your baby is adding approximately 220–250g per week at this stage as fat stores build for temperature regulation and energy after birth.
Your Body at Week 33
- ● As week 33 approaches, you may notice increased pelvic pressure as the baby descends and the head engages in the pelvis.
- ● Nesting instincts often kick in — a strong urge to clean, organize, and prepare your home for the baby's arrival is a common and normal experience.
- ● Cervical changes may begin; your doctor or midwife will monitor effacement and dilation at prenatal visits from this point onward.
- ● Braxton Hicks contractions are intensifying and may become more uncomfortable — rest, hydration, and position changes typically provide relief.
- ● Frequent urination returns with increased intensity as the baby's head descends deeper into the pelvis and puts pressure on the bladder.
- ● Trouble sleeping is nearly universal at this stage — consider short naps, a wind-down routine, and relaxation techniques to maximize the rest you do get.
Week 33 Checklist
- ☐ Pack your hospital bag if not already done — aim to have it ready by 35 weeks but earlier is better.
- ☐ Install the infant car seat and have it inspected at a certified car seat safety check station.
- ☐ Finalize your birth plan: pain management preferences (epidural, nitrous oxide, unmedicated), pushing positions, and newborn care choices such as delayed cord clamping and skin-to-skin.
- ☐ Choose your pediatrician and confirm they accept your insurance — schedule a prenatal meet-and-greet visit.
- ☐ Confirm you have received your Tdap vaccine (whooping cough booster), ideally between weeks 27–36.
- ☐ Practice relaxation and breathing techniques for labor: slow breathing, visualization, and hypnobirthing exercises can be effective labor coping tools.
Frequently Asked Questions
What should I expect at 33 weeks pregnant?
At 33 weeks pregnant, you are in the third trimester. Your baby is about the size of a Pineapple (43.7 cm) and is developing immune function, near-mature lungs, and positioning for birth. Common symptoms include pelvic pressure, nesting urge, frequent urination, intensifying Braxton Hicks contractions, and difficulty sleeping. Always consult your healthcare provider for personalized guidance.
How big is my baby at 33 weeks?
At week 33, your baby is approximately 43.7 cm in length and weighs around 1918g — roughly the size of a Pineapple. These measurements are averages based on WHO fetal growth charts; individual babies vary naturally in size.
What is the nesting instinct and is it medically significant?
The nesting instinct is an overwhelming urge to clean, organize, and prepare the home before birth. It typically intensifies in the last 4–6 weeks of pregnancy and is thought to be driven by hormonal changes involving oxytocin and estrogen. While it is harmless, it is important to avoid overexertion — delegate heavy tasks and avoid chemical-heavy cleaning products. Nesting can also be a sign that labor is approaching, particularly if it comes on suddenly.
How do Braxton Hicks contractions differ from real labor at 33 weeks?
Braxton Hicks contractions are typically irregular, do not increase in frequency or intensity over time, and ease with rest, hydration, or a warm bath. True labor contractions follow a pattern: they come at regular intervals, grow longer and stronger, and do not stop with rest. If contractions are more frequent than 4–6 per hour before 37 weeks, are accompanied by fluid leaking or bleeding, or do not resolve with rest, contact your provider immediately.
What does lightening feel like at 33 weeks?
Lightening refers to the baby dropping lower into the pelvis in preparation for birth — also called engagement. When it happens, women often report breathing becoming easier as the uterus no longer presses as hard against the diaphragm. However, increased pelvic pressure, a sensation of heaviness in the pelvis, and more frequent urination typically accompany it. In first-time mothers, lightening may occur weeks before labor; in subsequent pregnancies, it may happen just hours before delivery.
Track Your Exact Pregnancy Week
Use our free Pregnancy Week Tracker to find out exactly how far along you are based on your last menstrual period or due date.
Track My Pregnancy →Sources
- ACOG
- WHO Fetal Growth Charts
- Mayo Clinic
Medical disclaimer: This content is for informational purposes only and is not intended as medical advice. Always consult a qualified healthcare provider for guidance specific to your pregnancy.