First trimester: weeks 4 to 13
The first trimester runs to the end of week 13. It is when the baby's main organs and body systems start to form, and many people feel tired, queasy or both.
4 weeks 5 weeks 6 weeks 7 weeks 8 weeks 9 weeks 10 weeks 11 weeks 12 weeks 13 weeks
Second trimester: weeks 14 to 27
The second trimester covers weeks 14 to 27. Many people find it the more comfortable stretch, and baby movements are often first noticed around this time.
14 weeks 15 weeks 16 weeks 17 weeks 18 weeks 19 weeks 20 weeks 21 weeks 22 weeks 23 weeks 24 weeks 25 weeks 26 weeks 27 weeks
Third trimester: weeks 28 to 40
The third trimester runs from week 28 until birth. The baby gains most of its weight now, and your body prepares for labour.
28 weeks 29 weeks 30 weeks 31 weeks 32 weeks 33 weeks 34 weeks 35 weeks 36 weeks 37 weeks 38 weeks 39 weeks 40 weeks