Fetus – The name given to the embryo after the first three months of gestation

The embryo develops inside the cavity surrounded by a membrane called amnion.

Placenta – an organ made up of cells from the embryo and the mother◦ Allows the embryo to receive nutrients and oxygen and

removes carbon dioxide and other waste◦ Acts as a defense barrier◦ Secretes the hormones responsible for fetal development and

controls the changes in the mother’s body

The trophoblast secretes enzymes that erode the uterine walls and make the implantation of the embryo easier

The embryo buries itself into the vascular layer of the uterus and the placenta starts to develop

The placenta receives substances from the mother and removes the embryo’s waste.◦ It also acts as a filter for the substances that are not meant to

reach the embryo. However, some small molecules (drugs, tobacco, toxins, alcohol,

certain medicines, and viruses) may still reach the fetus

The embryo’s cells start to specialize On day 16, the neural tube (precursor to the central

nervous system) appears One of the most important processes in this phase is

cellular migration – cells change their position inside the embryo

From day 19, the somites (precursors to the spine) develop

Around day 20, the structure of the future heart appears; it starts beating around day 25

The connection between the embryo and the placenta now takes place through a tube (later known as the umbilical cord)

Between day 25 and 40, the brain begins to develop and the face, ears and neck are visible

The precursors to the digestive organs, lungs, and kidneys start to appear

From day 61, the embryo becomes a fetus◦ Almost all parts of the future individual are present

At week 28, the fetus measures around 35 cm and weighs more than a kilogram.

Inside its brain, folds are forming, which make it possible to increase the area of the brain within the same volume (which is key to intellectual development)

8 weeks 12 weeks

32 weeks

Childbirth consists of three phases:◦ Phase 1: Also called dilation phase, because uterine

contractions widen the neck of the uterus The amnion breaks and releases the amniotic fluid

◦ Phase 2 Uterine contractions before stronger, longer and more frequent.

The mother also contracts her abdominal muscles. Between these two forces, the baby is pushed out of the womb

Once the baby is born, its umbilical cord is clamped and its general state of health is checked

◦ Phase 3 The last contractions of the uterus push the placenta out of the

mother’s body (about 15 minutes after the baby is born)

A Caesarean, or C-section, is a surgical operation in which the baby is taken out of the mother’s body by means of an incision

This is done when the baby is unable to be born in the normal way, whether this is due to the health of either the mother or the baby