The three pregnancy trimesters last around about 266 days from conception. This means that on average your three pregnancy trimesters will cover about 40 weeks from the first day of your last period (LMP).
During your pregnancy you'll often hear reference being made to pregnancy trimesters. This section will outline the different stages of pregnancy, pregnancy trimesters, what to expect in each trimester and the changes both you and your baby will experience during your pregnancy.
Our pregnancy online forums are bursting with women at all different pregnancy trimesters and beyond. Read what they have to say and don't forget to join your birth club where women due in the same month as you meet and chat.
You Pregnancy Trimesters Week By Week
First Pregnancy Trimester
Second Pregnancy Trimester
Third Pregnancy Trimester
The Pregnancy Trimesters Stages Outlined
This is the way the stages of your baby's growth in the womb are measured. Each pregnancy trimester is roughly three months long: the first and second trimesters are 13 weeks and the third trimester, 14 weeks.
Each of the pregnancy trimester brings new changes for you and your growing baby: morning sickness in the first trimester, because of pregnancy hormones; in your second trimester, you'll be lucky enough to feel your baby move in the womb for the first time; and in the third, you might feel breathless as your baby begins to take up rather a lot of space, pushing everything else out of the way. These are all part and parcel of pregnancy: think about the changes changes your baby has to undergo during the nine months! Starting as an embryo no longer than 2mm in length at five weeks, by the time you reach 36 weeks, your baby is fully mature and up to 50cm long.
A normal or 'term' pregnancy typically lasts for 280 days, or 40 weeks (which is roughly nine calendar months) and is calculated from the first day of your last menstrual period, or LMP. The reason for this is because the exact date of conception can be hard to pin down, although in women with regular four-weekly cycles, conception has usually occurred two weeks after your LMP. You'll find that healthcare professionals refer to completed weeks of pregnancy. Again, they calculate this from the first day of your LMP.
Pregnancy isn't 'one size fits all'. Every pregnancy is different, and your baby will develop at his/her own pace. Making regular antenatal visits, and talking to your healthcare professional will help to reassure, and to ensure that you and your baby get the care that you both need.