Pregnancy is a time of incredible growth and change, both for you and your baby. For expecting mothers and parents-to-be, understanding the week-by-week milestones can be both exciting and reassuring. From the size of a sweet pea to the length of a leek, the growth of your baby is an amazing process. Join us as we take a closer look at this extraordinary journey.
Discover more about each trimester:
- First Trimester Of Pregency What To Expect
- Expecting the Unexpected: Navigating Your Second Trimester with Ease
- Navigate Your Third Trimester With Ease
Week 1 & 2
Technically, during the first two weeks of your pregnancy, you haven’t yet conceived. These weeks represent the time of your menstruation and the preparation for ovulation.
Week 3
Fertilization occurs, and your baby is now a tiny cluster of cells called a blastocyst. It’s about the size of a pinhead.
Week 4
The blastocyst has implanted in your uterine lining. It’s now an embryo and roughly the size of a poppy seed.
Week 5
Your baby’s heart starts to beat. Although still tiny, being about the size of an orange seed, the foundational structures of the brain, spinal cord, and heart are forming.
Week 6
Resembling more of a sweet pea in size, your baby develops nubs which will grow into little arms and legs.
Week 7
Facial features begin to take shape. The baby is about the size of a blueberry now. Tiny nostrils and eye lenses start to form.
Week 8
Nerve cells are branching out, and the baby resembles a kidney bean, now measuring close to half an inch.
Week 9
The bones of your baby start to harden from cartilage to bone tissue. Your little one is about the size of a green olive.
Week 10
Your baby’s size is comparable to a strawberry, and the foundations for its teeth are forming. You might be ready for your first ultrasound.
Week 11
With a length close to that of a Brussels sprout, your baby now has fingers and toes which are no longer webbed.
Week 12
Entering the last week of the first trimester, your baby is the size of a lime and has more defined facial features.
Week 13
Your baby is now as big as a pea pod. Vocal cords are developing, and tiny fingerprints are forming.
Week 14
Your baby is developing soft, fine hair called lanugo. In size, it’s comparable to a lemon.
Week 15
The baby begins to move, although you might not feel it yet. Roughly the size of an apple, it’s busy practicing breathing and swallowing.
Week 16
Your little one is now the size of an avocado. Its eyes are beginning to work and can make side-to-side movements.
Week 17
About as big as a pomegranate, your baby’s cartilage is turning to bone, and fat stores begin to develop.
Week 18
The baby is about the size of a sweet potato. You may start to feel slight movements as the baby gets more active.
Week 19
Approaching the size of a mango, your baby’s senses are developing, and it can hear your voice.
Week 20
You’re at the halfway point! The baby, now the size of a banana, might make you feel kicks as it becomes more active.
Week 21
The baby can swallow now and is as big as a carrot. It’s absorbing sugars from the amniotic fluid.
Week 22
The size of a papaya, your baby’s grip is becoming more refined, and it’s starting to look more like a newborn.
Week 23
At about the size of a large mango, the baby’s hearing is well-developed, and it may startle at loud sounds.
Week 24
Your baby is about the length of an ear of corn. Its brain is rapidly developing, and taste buds are forming.
Week 25
At the size of a rutabaga, the baby’s hair is becoming thicker, and it may respond to your touch through movement.
Week 26
Now the size of a scallion, your baby’s lungs are developing rapidly in preparation for breathing.
Week 27
Entering the third trimester, your baby is about as big as a head of cauliflower and can open and close its eyes.
Week 28
Weighing about as much as an eggplant, your baby’s brain is busy developing billions of neurons.
Week 29
The baby’s muscles and lungs are maturing, and it’s about the size of a butternut squash now.
Week 30
At around 15 inches long, the size of a large cabbage, your baby is gaining weight and is very active.
Week 31
The size of a coconut, your baby’s senses are fully developed, and it’s moving into the head-down position for birth.
Week 32
Your baby, the size of a jicama, is getting ready for its descent and may have a full head of hair.
Week 33
About the size of a pineapple, your baby’s bones are hardening, and it might have a wake/sleep schedule.
Week 34
The baby is roughly the size of a cantaloupe. Its skin is becoming less wrinkled as fat accumulates.
Week 35
Comparable to a honeydew melon in size, your baby’s kidneys are fully developed, and liver function is maturing.
Week 36
The size of a head of romaine lettuce, your baby is shedding most of the lanugo and vernix caseosa.
Week 37
Considered early-term, the baby is the size of a stalk of Swiss chard and may weigh around 6.5 pounds.
Week 38
Nearing the due date, your little one is as long as a leek and continues to build fat layers for warmth and energy.
Week 39
About the size of a small pumpkin, your baby is full-term and may arrive any day now.
Week 40
Congratulations, you’ve made it to your due date! Your baby, possibly weighing 7 to 8 pounds, is ready to meet the world.
We hope this guide helps paint a vivid picture of your baby’s weekly development throughout your pregnancy. Remember, every baby grows at their own pace, and these sizes are just averages. If you have any concerns or questions about your baby’s growth, be sure to consult your healthcare provider.
Wishing you a healthy and happy pregnancy!
For advice of support during pregnancy take a look at nhs.uk
We have lots more information on how to get pregnant or how to care for your newborn on our Parenting Tips page.
