First trimester
Weeks 1–13
Everything about the First trimester: your baby's development, how you may feel, and what to expect week by week.
The First trimester month by month
Month 1Weeks 1–4
Everything about month 1 of pregnancy: weeks 1 to 4, your baby’s development, the changes you may notice, and practical tips for each week.
By the end of the month your baby is about the size of a poppy seed, around 0.1 cm and 0 g.
- Week 1There is no baby yet this week, because doctors count pregnancy from the first day of your last menstrual period. Right…
- Week 2There is still no baby this week, but your body is approaching ovulation. An egg is maturing inside the ovary and the…
- Week 3This is the week when fertilization may actually take place. When sperm meets egg, they form a single cell that already…
- Week 4a poppy seedYour baby is now too small to see, about the size of a poppy seed, and is called a blastocyst that has just implanted…
Month 2Weeks 5–8
Everything about month 2 of pregnancy: weeks 5 to 8, your baby’s development, the changes you may notice, and practical tips for each week.
By the end of the month your baby is about the size of a raspberry, around 1.6 cm and 1 g.
- Week 5an apple seedYour baby is now about the size of an apple seed and beginning to take on a small elongated shape. The neural tube…
- Week 6a sweet peaYour baby is now about the size of a sweet pea and developing very quickly. The tiny heart has begun to beat and its…
- Week 7a blueberryYour baby is now about the size of a blueberry and nearly doubling in size each week. The brain is developing rapidly…
- Week 8a raspberryYour baby is now about the size of a raspberry and looking more and more like a tiny human. Fingers and toes are…
Month 3Weeks 9–13
Everything about month 3 of pregnancy: weeks 9 to 13, your baby’s development, the changes you may notice, and practical tips for each week.
By the end of the month your baby is about the size of lemon, around 7.4 cm and 23 g.
- Week 9cherryAt week 9 your baby is about the size of a cherry and is moving from the embryo stage toward becoming a fetus. The…
- Week 10strawberryYour baby is now about the size of a strawberry and has officially become a fetus, with most of the essential organs…
- Week 11limeYour baby is now roughly the size of a lime, with a head that's still fairly large compared to the body. Tiny nails are…
- Week 12plumYour baby is now about the size of a plum, and this is a special milestone: most of the essential organs are formed and…
- Week 13lemonYour baby is now about the size of a lemon, and this is the last week of the first trimester. The vocal cords are…
This guide is for general information and reassurance — it isn't medical advice. Always follow your doctor or midwife for your own pregnancy.