Christopher’s Journey.

Your baby measures about 3.5 cm (or 1.4 inches) and weighs about 5 grams (or 0.18 ounces). By the end of this week all your baby’s major organs will be in place. Over the following months before birth, they will continue to grow and mature.

Your baby’s legs are now longer than their arms and the large muscles in their arms and legs have developed, forming thick bands of padding between their skin and underlying bones. Your baby’s brain and nervous system are maturing, their muscles and nerves now working together to facilitate your baby’s first movements. Initially the movements are only small, jerky and uncoordinated and the baby is far too small for the mother to feel any movements within. Your baby now has primitive reflexes and can respond to touch if stroked on the palm of their hands or the soles of their feet.

Your baby can now open their jaw and stretch. Their body is straighter and small ribs can be seen through their chest. Their digestive system is developing rapidly and they are about to have a growth spurt!

Your baby now measures more than 2.5 cm from crown to rump (or 1 inch) and the webbing between their fingers and toes has now disappeared, creating separate digits. Your baby’s nail beds are starting to form, but actual nails will not be present until they are about 20 weeks.

Your baby’s heart now has 4 distinct chambers as well as the valves within their aorta and pulmonary blood vessels. These direct blood flow ‘one way’ to and from their body and lungs. The yolk sac has now disappeared and your baby’s blood is being produced by their liver. Their blood production will eventually be taken over by their bone marrow, once their bones fully mature. Your baby’s lungs are growing, as the ‘bronchi’ branch out, spreading through their chest.

Your baby is now developing elbows, knees, wrists and ankles. Their bones are initially soft and flexible (made of cartilage) and muscle tissue is now forming between their skin and bones. Your baby’s neck is more developed, allowing them to slightly lift and turn their head! Your baby may now be able to touch their own face with their hand (the beginnings of thumb sucking!)

Your baby now has an anus and their ovaries or testes are well developed. However, both sexes look the same at this early stage because their external sex organs are just beginning to form.

Your baby has grown to measure 1.5 cm (or 0.6 inches) and their head is now more rounded, making up about 25% of their entire body. Your baby’s face is becoming recognisably human. Their cheeks, mouth, lips and chin are more defined, and they now have nasal passages that create the tip of their nose. Your baby develops eyelids this week, which will remain fused and closed until they reach 24 weeks of pregnancy.

The internal and external parts of your baby’s ears begin to form, including their middle ear which is responsible for their hearing and balance. However, your baby will not be able to hear until they are somewhere between 19 to 24 weeks. Your baby now has immature taste buds on their tongue and under their smooth, translucent skin many tiny blood vessels can be seen networking through their body.

Your baby’s skeleton is starting to form and their arms and legs are now longer, extending forwards and across their body, appearing slightly bent. Your baby’s hands and feet now have 5 ridges on each, separated by narrow grooves, making them appear webbed.

Your baby has more than doubled in size during the last week, to be just over 1 cm in length (or 0.4 inches) and is now looking more human. Each eye now has an optic cup, retina and lens and your baby’s nasal pits are now present. These will extend to become their nostrils. Your baby’s inner ears and tongue are starting to form and their upper jaw and palate come together this week, fusing as one. (If this fails to happen, the baby may be born with a cleft lip and/or palate.)

Your baby’s tadpole-like ‘tail’ is noticeably receding and their trunk is now slightly straighter. Your baby now has a pancreas and an appendix and the beginnings of their reproductive organs, although not distinctly male or female yet. By the end of this week a fine, transparent layer of skin covers their body and their fingers (although still webbed) are now being defined as distinct thumbs and fingers.

Your baby’s crown to rump length is about 5 mm (or 0.2 of an inch) and their facial features are gradually building up around a wide mouth. Their lower jaw forms first, shortly followed by their upper jaw. Your baby’s head and forehead are comparatively large and their brain is now forming within, with the start of bulging eyes on each side of their head. Some scientists have compared the look of unborn babies at this stage to that of E.T!

Your baby’s limbs start to lengthen to form arms and then legs, with their hands and feet resembling ridged paddles, that will eventually become fingers and toes. Their internal organs are also taking shape. Their gullet (or ‘oesophagus’), stomach, kidneys and bowel are being defined, as well as 2 small buds which will form into lungs. Their heart is forming chambers and is beating away efficiently at 120 to 180 beats per minute! An ultrasound at this stage can detect an unborn baby’s heart beat relatively easily, unless the pregnancy is less advanced than first thought.

You are now 5 weeks pregnant (21 days after conception), which is the beginning of week 6. This is when the woman’s period is 1 week late. By now, you may begin to wonder if you are pregnant, or a pregnancy test may confirm that you definitely are! I

During week 6, your baby’s heart develops and first begins beating at around 24 days after conception. At this point, their heart is simply a long tube, rhythmically expanding and contracting. By the end of the 10th week their heart will have its various chambers and valves and be connected to a network of blood vessels supplying your baby’s body. The baby’s blood is initially produced by the yolk sac. Their blood stream remains completely separate from their mother’s. They do not mix, with the baby often having a different blood type from their mother and/or father.

Your baby’s neural tube now closes at the top (over their brain) and over the base of their spinal cord. This is an important time for the mother to have sufficient folic acid in her diet to support this process and avoid neural tube defects. During this week, small hand and feet buds start sprouting from your baby’s upper and lower body. Their body stalk elongates and starts to form 2 arteries and a vein inside, creating their umbilical cord, which will transport oxygen and nutrients from mother to baby and take away carbon dioxide and waste products from baby to mother. These are filtered through the placenta, along with many other substances that may be in the woman’s system (such as nicotine, alcohol, vitamins, herbs or medications).

At this early stage, an ultrasound image may only show a gestational sac and a heart beat may not be detected yet. During the next week your baby becomes visible and is seen to be bent and curled in the shape of the letter C.

You are now 4 weeks pregnant (14 days after conception), which is the beginning of week 5. This is when the woman’s next period would have been due (and is now late!) The blastocyst is now called an ‘embryo’, and your baby inside measures about 1.5 mm (or 0.06 inches). On day 18 after conception, your baby’s spinal cord and brain (called the ‘neural tube’) begin to form. The top layer of cells (or the ‘ectoderm’) forms the back of the embryo. It is a flat sheet of cells that folds in the middle and curls around to start forming a tube (which will house your baby’s spinal cord). The top end of the tube balloons out and enlarges to form the beginnings of your baby’s brain (although it is quite primitive at this point). By the end of this week (day 21 after conception), the 2 sides of the ‘sheet’ meet and fuse to complete the neural tube.

At the same time, the endoderm (or bottom layer of cells) balloons out the front of your baby at chest level, to form a yolk sac and a body stalk protrudes from your baby’s waistline. The body stalk is the beginning of your baby’s umbilical cord that will nourish them once the placenta is fully developed. In the meantime, the yolk sac provides some nourishment and is eventually reabsorbed into your baby’s body to form their bowel, liver, lungs and bladder. The yolk sac is also where the baby will start producing their own blood supply.

The earliest time possible to detect a pregnancy with ultrasound images is about 5 ½ weeks. A tiny sac can be seen, but the baby and their heart beat are not able to be detected yet. Sometimes a pregnancy of this stage is missed by an ultrasound, because the sac is so tiny.