The Size of Your Uterus During Pregnancy: A Week-by-Week Guide
Lucy Woodbridge
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What is the uterus?
Positioned just above the vagina, it measures approximately 7 cm in length and 5 cm in width at its broadest point. It’s located between the bladder and the rectum, and it’s kept in place within the pelvis by several ligaments.
Also within the pelvis are the other internal parts of the female reproductive system, including the vagina, the ovaries, and the fallopian tubes. The external parts are collectively known as the vulva.
On a monthly basis, the uterus sheds its lining. This results in menstruation, commonly referred to as a period.
Where is the uterus located when you’re not pregnant?
When you’re not pregnant, your uterus sits within the pelvis, which is the area below the abdomen and between the hip bones.
You have 3 layers to your uterus:
The perimetrium. This is the thin lining connecting the uterus to your body.
The myometrium. This is a thicker layer of muscle on the outside of your uterus, and is important for contractions during childbirth.
The endometrium. This is the layer of your uterine wall that sheds monthly when the released egg isn’t fertilised (also known as your period).
What happens to the uterus when you’re pregnant?
During pregnancy your uterus grows an astonishing amount. It goes from being quite a small little pocket of muscles to stretching right up into your ribs. Week by week, your uterus expands as your baby develops.
Amazingly, during pregnancy your internal organs move out of the way as your uterus grows, creating space for your baby. This might mean you find that you’re a little short of breath or can’t eat as much as usual, because the capacity of your lungs is limited as a result of the reduced space, and your stomach can’t expand as it normally would. But this is all for a reason – to make way for your baby!
The size of your uterus during pregnancy: a week-by-week guide
It’s impossible to say exactly how big your uterus will be at every stage of pregnancy, because it’s a physiological process that’s hard to predict. You may have heard that by week 40 your baby is the size of a watermelon – but this is completely inaccurate. Remember that your uterus contains your baby plus amniotic fluid, tissues, fats, and your placenta – all of this collectively might be the size of a watermelon, but not your baby alone!
So, to gauge the size of your uterus (not your baby) – let’s use fruit and veg to make some comparisons! We’re going to start at week 4, because from weeks 1-3 you’re not pregnant yet, or could still be ovulating.
Week 4: a poppy seed – 0.01 inches
Week 5: an apple seed – 0.05 inches
Week 6: a sweetpea – 0.14 inches
Week 7: a blueberry – 0.51 inches
Week 8: a raspberry – 0.62 inches
Week 9: an olive – 0.98 inches
Week 10: a prune – 1.21 inches
Week 11: a strawberry – 1.60 inches
Week 12: a lime – 2.14 inches
Week 13: a lemon – 2.95 inches
Week 14: a satsuma – 3.40 inches
Week 15: a pear – 3.99 inches
Week 16: an avocado – 4.58 inches
Week 17: an onion – 5.15 inches
Week 18: a cucumber – 5.60 inches
Week 19: a mango – 6.04 inches
Week 20: a sweet potato – 6.54 inches
Week 21: a banana – 10.52 inches
Week 22: a red pepper – 10.85 inches
Week 23: a grapefruit – 11.39 inches
Week 24: a pomegranate – 11.82 inches
Week 25: an eggplant – 13.63 inches
Week 26: an acorn squash – 14.03 inches
Week 27: a cabbage – 14.42 inches
Week 28: a lettuce – 14.82 inches
Week 29: a cauliflower – 15.05 inches
Week 30: a broccoli – 15.20 inches
Week 31: a coconut – 15.80 inches
Week 32: a cantaloupe – 16.20 inches
Week 33: a butternut squash – 16.80 inches
Week 34: a pineapple – 19.50 inches
Week 35: a romaine lettuce – 20.01 inches
Week 36: a bunch of kale – 20.80 inches
Week 37: canary melon – 21.20 inches
Week 38: small watermelon – 21.50 inches
Week 39: honeydew melon – 22.10 inches
Week 40-42: small pumpkin – 22.50 inches
What happens to the uterus during labour?
During labour, the muscles in the uterus physically move up with every contraction until they’re gathered right at the top, helping to open the cervix for the baby to come out. When you’re fully dilated, those muscles at the top of the uterus begin to push your baby down through the birth canal.
After birth, something incredible happens. The uterus starts contracting and getting smaller again, fitting back into the pelvis. It’s like our bodies know just what to do to take care of us and our babies!
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