During your pregnancy you’ll often hear reference being made to pregnancy trimesters. Each trimester of pregnancy is associated with certain features and changes experienced in both you and your growing baby.
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 online forums are bursting with women at all different stages of pregnancy 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 congregate.
The Stages Outlined
A normal or ‘term’ pregnancy typically lasts for 280 days, or 40 weeks (which is roughly nine calendar months), if calculated from the first day of your last menstrual period (LMP). It can be divided into three main stages commonly known as trimesters. Each trimester lasts for roughly three months: the first and second trimesters comprise 13 weeks each and the third trimester lasts for 14 weeks. Trimesters represent growth of your baby rather than calendar months.
By convention, your pregnancy is referred to in terms of completed weeks of pregnancy (weeks from the first day of your last period), rather than weeks from conception, since the exact date of conception is often not known. In women with regular four-weekly menstrual cycles, conception usually occurs around two weeks after your LMP.
Your baby is referred to as an embryo for the first eight weeks of pregnancy (in fact for six weeks following conception). After this time your baby is called a fetus.
In a typical pregnancy, an embryo will grow from a minute size, roughly equivalent to a pinhead, to an average length of 50 cm and a weight of about 3.5 kg. At the same time, your body will change to accommodate and support your developing baby. The average weight increase for a pregnant woman is 10-12.5 kg (22-28 lb), with almost 70% of this put on in the last 20 weeks. However, if there are no serious underlying problems, even a weight gain of as much as 20 kg can be considered normal (remember, the more weight that you gain during pregnancy, the more difficult it will be to lose it after you have given birth!).
Each trimester of pregnancy is associated with certain features in you and your growing baby. A pregnant woman will undergo a series of changes that allow her to support her pregnancy, nourish her developing baby and prepare her for breast-feeding. These changes are influenced by increased levels of various hormones, principally oestrogen, progesterone, human chorionic gonadotrophin (hCG) and human placental lactogen (hPL).
Remember that every woman and pregnancy is unique, and different babies develop at their own pace, so don’t worry if you find that certain things you experience or feel vary from those of a previous pregnancy, another pregnant woman or what you read.
Attending regular antenatal check-ups, and/or informing your healthcare professional if you feel that something isn’t quite right, will help to reassure you as well as allowing any potential problems to be identified and addressed at an early stage.