Week 33: Lung Development
The thirty-third week is a time of active development of the lungs and respiratory system.
Baby size: Melon (135-140 mm)
Baby development
Little smarty with chubby cheeks
Your baby continues to grow actively and prepare for birth. He can already distinguish day from night thanks to how light penetrates through the wall of your belly.
What’s happening this week:
- Immune system: Actively receiving your antibodies for protection in the first months of life.
- Bones: Continuing to harden, except for the skull bones.
- Amniotic fluid: Its volume reaches its maximum. Now the baby’s weight will increase faster than the amount of amniotic fluid.
- Position: Most babies at this term already assume a head‑down position.
Your fetus weighs about 1.9 kg, and its length is over 43 centimeters.
Changes for mom
Wrist pain and nesting syndrome
Your body continues to surprise you with new sensations, and instincts are preparing you for meeting the baby.
What you may notice:
- Carpal tunnel syndrome: Swelling can press on the nerves in the wrists, causing numbness or tingling in the fingers.
- Increased "nesting": The desire to clean, cook, and set up the home may reach a peak.
- Fatigue and insomnia: Finding a comfortable sleeping position becomes a real quest.
- Weight gain: You continue to gain weight steadily.
It’s important to take care of yourself and your comfort. Learn more about coping with discomfort in the article "Physical changes of the body during pregnancy".
Overview
Week 33: Immune System and Strong Bones
In the thirty-third week your baby receives a powerful boost of immunity from you. Your antibodies are transferred to him through the placenta, creating reliable protection against illnesses during the first months of life.
He is now the size of a pineapple. His skeleton continues to harden, so now, more than ever, it is important that you get enough calcium. The bones of the skull remain soft and unfused, allowing the head to pass safely through the birth canal.
For you, this is a week when you may feel "big" and clumsy. The growing uterus presses on all organs, causing shortness of breath, heartburn, and frequent trips to the bathroom. Rest is your main task.
Transfer of immunity is a wonderful gift of nature. You share your protection with the baby, helping him stay healthy in a world that is new to him.
You are on the home stretch. To know what to prepare for at this stage, read our detailed overview "Third Trimester: What You Need to Know".
Tips for mom
Preparing the space and the body
This is a great time to finish setting up the "nest" and pay attention to your body.
What to do:
- Set up a feeding area. Prepare a comfortable chair, a nursing pillow, and a table for essentials (water, phone, snack).
- Do hand exercises. If you’re bothered by wrist pain, do gentle stretching exercises.
- Discuss the baby’s position with the doctor. At the scheduled visit the doctor will check whether the baby is in the correct position.
- Finish shopping. Make sure you have everything needed for the baby’s first weeks of life.
Creating a comfortable space will help you get into a positive mindset. Ideas can be found in the article "Preparing the home and the room".
Tips for partner
Main helper in "nesting"
Your practical help right now is worth its weight in gold. Help your partner realize her ideas for setting up the home.
Your contribution to the joint effort:
- Be a "handyman". Assemble the crib, install the changing table, hang shelves.
- Go shopping together. Help her choose and carry heavy items.
- Be patient. The nesting instinct can make her very demanding. Approach it with understanding.
- Review your action plan for the "D‑day". Make sure both of you know what to do when labor starts.
Readiness for labor is also your responsibility. Reread the article about signs of the start of labor, to be fully prepared.
Checklist
Your action plan for week 33
The finish line is getting closer.
- ✅ Finish setting up the baby’s room or corner.
- 🤱 Arrange a comfortable feeding spot.
- 🛒 Make the final purchase of necessary items for the baby.
- 鈣 Make sure your diet contains enough calcium.
- 🚗 Check that the car seat is installed correctly.
- 📚 Refresh your knowledge about newborn care, for example by reading the article about spit-ups in infants.