Congratulations on your pregnancy! Your body is going to go through some phenomenal changes over the next 9 months as it allows your baby to grow and develop. Understanding what’s happening to both you and your baby will go a long way to help you feel at ease. This article is going to take a closer look at the foetal development during the all-important first trimester of pregnancy.
Weeks 1 and 2
Conception usually occurs around two weeks after your last period and so during these weeks, you’re not actually pregnant! However, your health care provider will count these initial two weeks towards your due date until you can have a more accurate scan.
This is when fertilisation takes place and the sperm joins with the egg to form a zygote. The zygote consists of 46 chromosomes – 23 from the mother and 23 from the father – to determine its gender and other characteristics.
At week 4, the gestational sac will begin to form and this will eventually become part of the placenta. Other cells will be for the amniotic sac which will provide cushioning to your baby whilst it develops. It’s at this stage your pregnancy test is likely to come back as positive!
Week 5 is crucial as this is when the cells that will form the heart and central nervous system will begin to develop. There will also be an increase in HCG hormone in your body that is often the first sign that you’re in your first trimester of pregnancy.
By week 6, your baby’s heart will begin to form, the neural tube that will contribute to the development of the brain and spinal cord closes up and your foetus takes on a curved C shape. By this stage there will also be a measurable heartbeat.
During week 7, your baby’s head will grow larger and become more identifiable. The brain and face will begin to develop and you will be able to see limbs taking shape. This is an important turning point during the first trimester of pregnancy as your baby gradually becomes more recognisable.
At this stage, fingers will begin to form – although initially they’ll look like paddles. Other features such as elbows and ears are also starting to take shape and there may be some small, jerky movements.
At week 9, facial features will continue to develop and become more prominent. Elbows will become more formed and toes will become visible.
By week 10, the umbilical cord is clearly visible and your baby will now be able to bend their elbows. Their fingers and toes will also lose their webbing and start to grow longer.
At week 11, many of your baby’s facial features will appear disproportionate to the rest of their body and red blood cells will begin to form your baby’s liver. This week also signifies when your baby’s genitalia will start developing.
By week 12, fingernails will begin to form and the genitalia will continue to develop – although they will not be visible on an ultrasound. The kidneys will also start to function and you may even find that your baby starts to suck their thumb!