Pregnancy week by week
Discover how your baby grows and how your body changes in every week of pregnancy. Pregnancy lasts 40 weeks divided into three trimesters, and each week brings its own signs.
Weeks are counted from your last menstrual period, not from when you took a test or first noticed something. Not sure which week you're in? Use the calculator below.
Calculadora de semanas de embarazo
Introduce la fecha de tu última menstruación
First trimester
Pregnancy Week 1: How the Weeks Are Counted
Pregnancy week 1 starts on the first day of your last period. I'll explain how pregnancy weeks are counted and why there's no baby yet at…
Pregnancy Week 2: Ovulation and Your Fertile Days
In pregnancy week 2 you ovulate. I'll explain when your fertile days are and what happens in this stage before conception.
Pregnancy Week 3: Fertilisation and Implantation
In pregnancy week 3, fertilisation and implantation happen. I'll explain what goes on in your body and why the test can still be negative.
Pregnancy Week 4: Symptoms, Tests and Baby Size
Find out what happens in pregnancy week 4: when to take the test, the first symptoms, the baby's size and the signs that everything is…
Pregnancy Week 5: Symptoms, Tests and Baby Size
Everything that happens in pregnancy week 5: when to take the test (it's time!), the first symptoms, the baby's size and tips for this moment.
Pregnancy Week 6: Symptoms, Ultrasound and Baby Size
Everything that happens in pregnancy week 6: the most intense symptoms, when you can see the heartbeat on your first ultrasound and the…
Pregnancy week 7: symptoms, ultrasound and baby size
Everything that happens in pregnancy week 7: the heart beats strongly, symptoms at their peak and how big your baby is. A calm, detailed guide.
Pregnancy week 8: symptoms, ultrasound and baby size
Everything that happens in pregnancy week 8: your little one is now the size of a raspberry…
Pregnancy week 9: symptoms, ultrasound and baby size
Everything that happens in pregnancy week 9: your little one is now the size of an olive, eyelids are forming and you're entering month…
Pregnancy week 10: symptoms, ultrasound and baby size
Everything that happens in pregnancy week 10: your baby is now the size of a strawberry, stops being an embryo and becomes a fetus.
Pregnancy week 11: symptoms, ultrasound and baby size
Everything that happens in pregnancy week 11: your baby is now the size of a fig, it's time for the nuchal scan, and nausea finally starts to ease.
Pregnancy week 12: baby size and end of first trimester
Pregnancy week 12 closes the first trimester: your baby is around 6 cm, the size of a lime, nausea eases and the risk drops.
Pregnancy week 13: symptoms, baby size and tips
Everything that happens in pregnancy week 13: your baby is now the size of a peach, the second trimester begins…
Second trimester
Pregnancy week 14: symptoms, baby size and tips
Everything that happens in pregnancy week 14: your baby is now the size of a lemon, grows fine lanugo hair and makes faces…
Pregnancy week 15: symptoms, baby size and tips
Everything that happens in pregnancy week 15: your baby is now the size of an apple, its skeleton is growing firmer…
Pregnancy week 16: symptoms, baby size and tips
Everything that happens in pregnancy week 16: your baby is now the size of an avocado, can start to perceive light…
Pregnancy week 17: symptoms, baby size and tips
Everything that happens in pregnancy week 17: your baby is now the size of a pear, starts to store fat…
Pregnancy week 18: symptoms, baby size and tips
Everything that happens in pregnancy week 18: your baby is now the size of a red bell pepper…
Pregnancy week 19: symptoms, baby size and tips
Everything that happens in pregnancy week 19: your baby is now the size of a mango, their skin is protected by the vernix and they're…
Pregnancy week 20: symptoms, baby size and tips
Everything that happens in pregnancy week 20, the halfway point: your baby is the size of a banana…
Pregnancy week 21: symptoms, baby size and tips
Everything that happens in pregnancy week 21: your baby is now the size of a carrot, tastes what you eat and their movements get stronger…
Pregnancy week 22: symptoms, baby size and tips
Everything that happens in pregnancy week 22: your baby is now the size of a papaya, has defined features and you can feel their…
Tools and calculators
What you'll find each week
Every weekly article follows the same structure, so you can jump straight to what you need:
- Your baby's development: how big it is, what it weighs and which organs are forming.
- Your symptoms: the most common ones that week and why they happen.
- What the scan shows when one is due, and which tests are coming up.
- Practical tips for those seven days in particular.
And if an easy size reference helps, each week uses an everyday comparison — from a poppy seed to a watermelon — so you can picture how much it has grown.
Frequently asked questions
How many trimesters are there?
Three. The first runs from week 1 to 13, the second from 14 to 27, and the third from 28 until birth. Each has its own symptoms and tests, and knowing which one you're in helps you understand what's coming.
When do symptoms start?
The first ones usually show up between weeks 5 and 6, once hCG is circulating in quantity. Tiredness is the most common, often ahead of nausea, which tends to appear a little later.
Why doesn't my week match my doctor's?
Because it's counted from the first day of your last period, not from conception. That means you weren't actually pregnant during the first two weeks — it's the standard way of counting and it avoids confusion.
What if I'm expecting twins?
Weeks are counted the same way, but monitoring is closer and some tests are brought forward. Your midwife or doctor sets the schedule for your case.
Every week we explain your baby's development, the most common symptoms and practical tips. If you have any questions about your pregnancy, remember this content is for information only: always consult your doctor.