The fetus is now around 2 inches long and weighs roughly 0.5-0.6 ounces.
All organs are in place and continue to mature until they are fully functional. Around week 13 of pregnancy, the vocal cords form in the larynx. Furthermore, your baby can already swallow and is practicing breathing by now – the chest rises and falls. However, it will continue to be supplied with oxygen by the umbilical cord until birth.
These exercises in the amniotic fluid are important for the organs, muscles, and joints to develop well, and for the baby to master all the skills that are vital after birth. Swallowing amniotic fluid helps teach the stomach, intestine, and kidneys how to function. The breathing movements train the lungs and the gymnastic exercises in the amniotic sac stimulate the muscles to grow.
Your baby is now about the size of a small peach.
The amniotic fluid itself serves not only as a "training ground" for development, but also like a cushion that provides protection against external influences, regulates heat, and prevents the fetus growing together with the sensitive fetal membranes.
By now, the yolk sac, which previously supplied the baby and produced blood cells, has fully dispersed – the liver, bone marrow, and spleen have taken over blood production.
What does the placenta do?
The placenta is now fully developed and supplies the baby via your bloodstream. Figuratively, the placenta can be imagined as a tree with many boughs, which in turn divide into many branches. These extensions have access to the mother's blood, enabling nutrients and oxygen to be supplied to the baby and toxins to be removed. Furthermore, the placenta is like a filter or protective shield against various pathogens and harmful substances (although not all of them!). The placenta also produces important hormones for pregnancy, birth and breastfeeding.
A good blood supply is essential for the placenta to perform these tasks, which are vital for the fetus. High blood pressure, smoking, and diseases can reduce blood supply and can therefore be detrimental to the baby's development.
Have you stopped having morning sickness? Then you will definitely be happy about being able to eat more food: Your body now needs roughly 300 additional calories (equivalent to around three bananas or a slice of bread with cheese). Weight gain varies greatly between women and depends not only on nausea in the early weeks but also on your starting weight. On average, you can expect to have gained around 6 pounds by now. Your baby bump may slowly also become visible now, depending on your physique.
You not only require more calories now, but you also need lots of vitamins and minerals. Talk to you doctor to find out whether you can get all your nutrients through your diet or whether a nutritional supplement is necessary.
Your veins may become visible under the skin due to the increased blood volume.
Although the pregnancy hormone HCG is decreasing, the remaining hormone production responsible for pregnancy is running at full speed – the placenta can now also work without help from the ovaries. The higher progesterone levels result in an increased constipation and low blood pressure.
Hormonal factors also increase the production of the skin pigment melanin. This causes the skin's pigmentation to become more pronounced, and the nipples and labia in particular to become darker.
If you are rather unhappy with this, do not worry: These changes usually disappear after pregnancy, just as quickly as they came.
Your pregnancy week by week, Prof. Lesley Regan, DK Limited London, 2019, p. 110 f.
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