Pregnancy usually lasts 40 weeks, counting from the first day of your last period and is grouped into three trimester. Find out everything about your baby’s development in the first trimester.
Week 1 – 2
The weeks of your pregnancy are calculated starting from the first day of your last period. This means that in the first two weeks or so, you aren’t actually pregnant. During this time your body prepares itself for ovulation, as any other month.
Conception usually takes around 2 weeks after your period during ovulation. When you ovulate, an egg gets released from the ovaries around two weeks after the first day of your period, depending on the length of your menstrual cycle.
Week 3 – 5
During the third week, your fertilised egg moves along the fallopian tube towards the womb. The egg begins as a single cell, which divides again and again, and by the time the egg reaches the womb, it has grown into a mass, that consist around 100 cells or more. At this point it’s classified as an embryo. Once the embryo reaches the womb, it burrows into the lining of the womb. This phase is called implantation.
During the 4th and 5th week, the embryo grows and develops within the lining of the womb. The embryo is attached to a tiny yolk sac that provides nourishment and is surrounded by fluid inside. It’s the outer layer of this sac that develops into the placenta. A few weeks later, the placenta will be fully formed and will take over the transfer of nutrients to the embryo.
During the 5th week, you’ll have noticed that you missed your period. By this time, the baby’s nervous system is already developing, and the foundations for its major organs are in place. At this stage, the embryo is around 2mm long.
The embryo’s outer layer of cells develop a groove and folds to form a hollow tube called the neural tube, which will eventually become the baby’s brain and spinal cord. The heart is also starting to form. In the beginning it is only a simple tube-like structure, but at this stage the baby already has some of its own blood vessels and blood begins to circulate. A string of these blood vessels connects the baby and mother. This bond later on will be known as the umbilical cord.
Week 6 – 7
By the 6th week of pregnancy, the embryo has developed a large mass where the heart is and a bump that will become the brain and the head. At this stage, the embryo is curved and has a tail.
The limbs are already visible in the form little swellings as they’ve started developing. Little dimples on the side of the head will become the ears, and there are thickenings where the eyes will be. By now the embryo is covered with a thin layer of see-through skin.
By the 7th week, the embryo has grown to about 10mm. The brain is starting to grow, that results in the head growing faster than the rest of the body. The inner ear starts to develop, however the outer ear on the side remain the same dimples.
Cartilages start to form inside the limbs, which are going to be leg and arm bones later on, and the shape of the limbs start to flatten out, to later form the hands. Nerve cells continue to multiply and develop as the the nervous system starts to take shape.
Week 8 – 9
By the time you’re 8 weeks pregnant, the baby is called a foetus. The legs are getting longer, but the different parts aren’t properly distinct yet.
The foetus is still inside its amniotic sac, still receiving nourishment, and the placenta is continuing to develop, so that it can attach to the wall of the womb later on.
By the 9th week, the baby’s face is slowly forming. The eyes are bigger and some pigmentation can be found in them. The a mouth and a tongue with tiny taste buds have also started developing. Tiny ridges identify where the fingers and toes will be on the hands and toes, although they haven’t separated out yet. Most major internal organs continue to develop. By this stage the baby has grown to about 22mm long in size.
Week 10 – 12
The ears and ear canals are starting to develop. The jawbones are forming and already contain all the future milk teeth.
At this stage, the heart has fully developed and the baby is making small movements that can be detected on an ultrasound scan.
During week 11, the baby grows quickly and the placenta is rapidly developing until it’s fully formed by week 12. The facial bones are formed, and the eyelids are closed. They won’t open for a few months yet.
Your baby’s head makes up one-third of its length, but the body is growing fast too. The fingers and toes are separating, with fingernails present. The body itself is also starting to straighten out.
The foetus is fully formed by the 12th week. All the organs, muscles, limbs and bones are in place, and the sex organs are well developed, although the sex of the baby can’t be told yet. The baby’s skeleton is made up of cartilage and it starts to develop into bone. From now on, the baby only has to grow and mature. You won’t be able to feel the baby’s movements yet, however rest assured, there’s plenty of movement!
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