GUIDE
Your baby's bones are hardening and their immune system is developing with help from your antibodies.
At 33 weeks your baby is the size of a pineapple, weighing about 4.25 pounds. Their bones are becoming stronger — except the skull, which stays soft and flexible for delivery. Your antibodies are crossing the placenta, giving your baby a head start on immune protection.
Be prepared from day one
Your baby is now about the size of a pineapple — roughly 17.2 inches long and weighing approximately 4.25 pounds. This week is all about strengthening and immune preparation.
Your baby's bones are hardening significantly this week, with one important exception: the skull. The skull bones remain separate and connected by flexible cartilage membranes called fontanelles — the "soft spots" you'll feel on your newborn's head. This design is intentional. During delivery, these skull plates can overlap slightly (called molding), allowing your baby's head to fit through the birth canal. It's one of nature's most elegant engineering solutions.
The immune system is an exciting development this week. Your antibodies — specifically IgG immunoglobulins — are actively crossing the placenta and entering your baby's bloodstream. This passive immunity means your baby will be born with some protection against the same diseases you're immune to, whether from vaccination or previous infection. This protection lasts for the first few months of life, bridging the gap until your baby's own immune system kicks in and begins responding to vaccines.
Your baby continues to gain weight rapidly, adding about half a pound per week. Most of this weight is fat — both the brown fat that will help regulate temperature after birth and the white fat that fills out your baby's limbs and cheeks. Your baby's skin is smoother and less wrinkled than even a week ago.
The lungs continue to mature. Surfactant production is increasing, and the air sacs are developing more completely. While a baby born at 33 weeks has excellent survival rates, the lungs benefit enormously from every additional week of development.
At 33 weeks, space is at a premium. Your uterus is pushing up against your rib cage and down on your bladder simultaneously, which explains why you might feel short of breath and need to pee at the same time.
A new symptom many people notice around this time is carpal tunnel syndrome — tingling, numbness, or aching in the hands and wrists, especially at night. This is caused by fluid retention putting pressure on the median nerve as it passes through the carpal tunnel in your wrist. It's annoying but usually temporary, resolving within weeks or months after delivery.
Braxton Hicks contractions may be more frequent and noticeable. Some people find them uncomfortable enough to pause what they're doing. Remember: if they become regular, progressively stronger, or don't stop with rest and hydration, call your provider.
Pelvic pressure is increasing as your baby grows and moves lower. This can cause a sensation of heaviness or "fullness" in your pelvis, especially when standing or walking. Support garments designed for pregnancy can help distribute the weight. You may also notice more swelling in your feet and ankles — elevation and compression socks can provide relief.
You may be feeling overheated more often. Your basal metabolic rate is significantly higher now, and the increased blood volume means your body generates more heat. Dress in layers, stay in air conditioning when possible, and keep cold water handy.
Sleep continues to be challenging. The combination of physical discomfort, frequent bathroom trips, anxiety, and hormonal changes makes quality rest elusive. If you can, nap during the day — your body needs the rest.
Every pregnancy is different. You may experience all, some, or none of these symptoms.
Seven weeks to go. You're in the home stretch, and preparation is shifting from abstract planning to concrete action.
Your body is doing something remarkable right now: passing antibodies to your baby through the placenta. This passive immunity will protect your newborn for the first few months of life. If your provider recommends a Tdap booster or flu vaccine in the third trimester, this is why — the antibodies you produce will cross to your baby.
Pregnancy-related carpal tunnel is caused by fluid retention that puts pressure on the median nerve in your wrist. If you're experiencing tingling, numbness, or pain in your hands — especially at night — try wrist splints, elevating your hands, and gentle stretches. It typically resolves after delivery.
If you started your birth plan last week, now is the time to refine it and discuss it with your provider. Make sure your preferences are realistic for your birthing facility. Remember that flexibility is important — birth rarely goes exactly as planned, and having a calm, informed approach to unexpected changes is just as valuable as the plan itself.
If you're interested in cord blood banking (storing your baby's umbilical cord blood), now is the time to research options and make arrangements. Cord blood contains stem cells that may be used in future medical treatments. You can bank privately (paid service) or donate to a public bank (free). Discuss the options with your provider.
When in doubt, call your provider. It's always better to check and be reassured than to wait and worry.
Next week at 34 weeks, your baby will be the size of a cantaloupe. Their lungs will be nearly mature, the vernix coating will be thickening, and the central nervous system will be making significant strides. It's also a great time to start thinking about your hospital bag.
Looking back, week 32 was when most babies turned head-down and the birth plan conversation started in earnest.
If you haven't started already, our guide on how to prepare for labor covers what you can do now to feel confident when the big day arrives.
Seven weeks is close. Your baby is growing stronger every day, building immunity, hardening bones, and preparing for the world. You're doing the same.
This guide is for informational purposes only and is not a substitute for professional medical advice. Always consult your healthcare provider with any questions about your pregnancy.
