33 weeks pregnant: symptoms and baby development
Brain and nerves fully developed.
Third trimesterMonth 85 min read
By Solesia, from public clinical guidanceUpdated
Quietly, under everything else, your baby is growing a proper skeleton. It is hardening all over, bone replacing the soft cartilage they began with, and there is one careful exception: the skull. Its plates stay separate and a little soft on purpose, so the head can shape itself to fit through the birth canal when the day comes. Their brain and nervous system are finished. You are carrying a few extra pounds of baby, water and placenta, and if the head is down you feel it as a settled weight low in your pelvis, a kind of quiet ballast for the seven weeks that are left.
How big is your baby at 33 weeks
About the size of a pineapple
17.2 in long·4.7 lb
Baby development at 33 weeks
At 33 weeks your baby measures about 17.2 inches from head to heel and weighs around 4.7 pounds, roughly a pineapple. Their bones are hardening as calcium is laid down, which is why your own need for it is high right now. The skull is the exception: its plates stay soft and unfused, sliding over each other during birth, and they do not close fully until well into the second year.
The brain and nervous system are fully developed, and they are busy. Your baby can tell light from dark through the wall of your bump, they respond to your voice, and their sleep now includes the rapid-eye-movement stage in which adults dream.
Fat keeps building, and their skin is pinker and smoother. Their immune system is taking on antibodies from your blood across the placenta, and that transfer speeds up over the last weeks, which is one reason the Tdap shot before 36 weeks does so much good. The amount of fluid around them has reached its peak and will slowly fall from here.
Your body at 33 weeks
A heavy, dragging feeling low in your pelvis is expected if your baby is head down, and it gets stronger the lower they settle. Sitting on a firm chair rather than a soft sofa helps, as does lying on your side to take the weight off. A maternity support belt eases it for some women; a warm bath at the end of the day does for others.
Practice contractions are common now, and expected: a tightening across the bump that lasts twenty to thirty seconds and then eases, at no particular interval. They may come more often after a busy day or when you need the bathroom. Change position, drink a glass of water, and they settle.
Sleep is broken for many reasons at once, and the tiredness that follows is part of the week. Keep the bedroom cool, get to bed earlier than feels necessary, and use pillows generously: under the bump, between the knees, behind the back. Swollen feet by evening are also expected; put them up, and keep walking during the day so the fluid keeps moving.
Common pregnancy symptoms at 33 weeks
- Pelvic pressure. The head settling low. A firm chair, side lying, and a support belt if it helps.
- Braxton Hicks. Painless tightenings with no pattern. A change of position and a glass of water.
- Backache. Weight in front and loose joints. Warmth, gentle stretching, and no heavy lifting.
- Swollen feet. Fluid gathering by evening. Feet up, and comfortable shoes a half size up.
- Broken sleep. Bladder, bump and baby. Pillows everywhere, and an earlier bedtime.
- Feeling hot. More blood, faster metabolism. Light layers, and a fan by the bed.
- Headaches. Tiredness and tension. Water, rest, acetaminophen if needed.
When to call your provider at 33 weeks
Painless tightenings are practice. Regular or painful ones before 37 weeks are worth a call, in case labor is starting early.
Two things are worth a same-day call at any point in pregnancy: bleeding that is more than spotting, and pain that is severe or does not ease. From the second trimester, add fluid leaking and any change in your baby’s usual pattern of movement. You do not need to be sure something is wrong to call; that is what the number is for.
What to do at 33 weeks
- Pack the hospital bag. Your ID and insurance card, your records, phone charger, loose clothes for you, a going-home outfit and a blanket for the baby. Keep it by the door from now.
- Install the car seat. A rear-facing infant seat, new or from someone you trust. Many fire stations and hospitals check installations for free; book it now rather than the week you are due.
- Numbers in your phone. Your provider’s office and after-hours line, the labor and delivery unit, and whoever is driving you. Save them where your partner can find them too.
- Tdap deadline near. The shot is given between 27 and 36 weeks; if it is still to come, ask at this visit so your baby gets the antibodies before birth.
Common questions at 33 weeks
What should I pack in my hospital bag?
For you: ID, insurance card and any paperwork, a phone charger, toiletries, a robe or loose clothes, comfortable underwear, nursing bras if you plan to nurse, and snacks. For the baby: a going-home outfit, a hat, and a blanket. The hospital supplies diapers and wipes for your stay. Leave the car seat in the car.
Why does my pelvis feel so heavy at 33 weeks?
If your baby is head down, the weight of their head rests on your pelvic floor, and the ligaments there are looser than usual. It is expected and gets more noticeable as they settle lower. Sitting on a firm surface, lying on your side and a support belt all take some of the load.
Is it too late for the Tdap vaccine at 33 weeks?
No. The window is 27 to 36 weeks, and earlier in it is better, but 33 weeks still gives your body time to make antibodies and pass them across the placenta before birth. If you have not had it, ask at your next visit.
How many months is 33 weeks?
Around eight months, at the start of the eighth. You are in the third trimester with seven weeks to your due date, and about four weeks from early term, when a baby born on their own schedule is considered ready rather than early.
Written from public clinical guidance, including NHS: Week 33, ACOG: How your baby grows, ACOG: Changes in your body, ACOG: The Tdap vaccine and pregnancy, ACOG: Preterm labor, NHS: Pelvic pain and NHS: Swelling in pregnancy. This page is general information, not medical advice, and does not replace your provider.