Baby's Development - First Trimester

First Trimester

Congratulations! You’re going to be a parent! You have embarked upon one of the most significant journeys of your life, welcome to the first trimester of pregnancy! This is the first 12 weeks or 10 weeks if you start from when your baby was conceived. Pregnancy is described as having 3 trimesters due to the development that is happening for your baby.

Something extraordinary is happening inside your body, a new life, is creating itself from the genetic gifts in the sperm and egg and from the type of internal environment that you provide your baby with as it develops over the next 9 months or so.

The two cells which met at conception have divided and divided again and just 18 days after fertilization (4 ½ weeks gestation) your baby’s nervous system begins to form. At this point your baby becomes highly susceptible to the impact of harmful chemicals or viruses in your partner’s body, whereas previously, when you probably didn’t even know you were pregnant, your little baby was less affected by these threats.

At this early stage, your baby’s heart cells have developed sufficiently for them to start to beat.

In this next 4 four week period, all your baby’s major organs are laid down in a primitive form. Your baby’s head makes up almost half of its size and a rudimentary brain develops which directs the first movements of your baby’s limbs.

By the end of the first trimester of pregnancy, your baby’s kidneys begin to function and the small amounts of amniotic fluid that it has been swallowing from its surroundings, are passed out of its body as urine. Your baby’s liver has been growing and accounts for 10% of your baby’s body weight. Your baby’s lungs are now able to make intermittent breathing movements, though your baby will receive all its oxygen via the placenta and cord until it is born, these movements are practice for when your baby takes its first breath on its birthday.