Pregnancy Week 5 – The Baby’s Progress

Pregnancy week 5 will see the first layer of skin appear protecting his developing internal organs. The head and brain are currently the most rapidly growing and are out of proportion to the rest of the body. The face and neck have taken shape with the earliest sign of the nasal plate in place although the jawline is yet to become defined.


5 Week Fetus

As this is still part of the critical development stage there is a lot going on with the organs this week. 30 somites will be in place by the end of pregnancy week 5 so the neural tube will have been zipped closed and the hindbrain, which regulates the heartbeat, breathing and movement will now been to form. As the embryo’s spinal cord begins to fold and fuse together your body will need to draw on all the reserves of folic acid that you have so it is essential to ensure that you have sufficient amounts of this in your diet.

It is suggested that 0.4mg (400 micrograms) a day are needed throughout your entire first trimester, ideally starting from around 12 weeks before conception takes place. Insuffecient amounts of folic acid can raise the chances of your baby having neural tube defects such as Spina Bifida by 50-70%. See what else can effect your baby’s development at this crucial time.

Tissue muscle has also now begun to form around the spine and back, increasing the width of the torso. The spinal cord is now defined by 3 sections: the ventricular, the mantle and the marginal with each zone being responsible for it’s own set of differentiated cell and neuron formation. It is said that the embryo is unable to experience any sensation until the nervous system takes shape and connects up to the nerves and muscles. Once this process has taken place, many believe that sensation is still not present until the brain has developed sufficiently enough in order to be able to process the information from the nerves.

The earliest signs of the pituitary gland’s frontal lobe appears, along with 2 ureteric buds that will later develop into the kidneys. The digestive layer begins to differentiate where the stomach, lungs, liver and pancreas are to be located. The esophagus (from where food is swallowed) has begun to form and lengthen and now has 2 lung sacs either side of it.

The undeveloped eyeballs, known as ‘optic vesicles’ appear in the optic cup and begin to increase in size and the upper limbs begin to lengthen and taper at the ends where the hand plates will begin later forming into the hands although at this stage, the hand plate, arm and shoulders are quite distinguishable in the limbs. The lower limb buds develop slower but are in place and nerve distribution has began throughout.

During pregnancy week five your embryo is now measuring in at around 0.28” (7 mm) crown to rump.

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(See 5 Weeks Pregnant – The Mother’s Progress)

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