Unit 4.6 pregnancy & 4.7 childbirth

• Biologie
• Middelbare school
• vwo
• Leerjaar 2

Pregnancy

• Pregnancy is the period of development from embryo to birth. 

• zygote = fertilized egg travels from the oviduct to the uterus

learning objectives

• What four stages in labour do we distuingish?
  
• What happens in each of these stages?

zygote -> morula-> blastocyst -> embryo

When?

7 days after fertilization there is the implantation of the embryo in the uterus lining. 

implantation

The first phase: embryo

• When an embryo reaches the uterus, it implants itself into the uterus lining.
• The uterus lining develops into a placenta, which is able to provide the nutrients and oxygen through the umbilical cord to the embryo. Through the umbilical cord the embryo get rid of waste. 

So the umbilical cord is the connection between the mother and the child. Different substances can pass from mother to child through the umbilical cord, like alcohol, drugs and even some virusses.

Membranes

2 thin membranes form the amniotic sac. The amniotic sac is filled with amniotic fluid.

Membranes

In the amniotic fluid the embryo floats.

placenta

The third phase: foetus

• After 2 months is the embryo is called a foetus. 
• The next 7 months the foetus will develop further into a fully grown baby.

So the umbilical cord is the connection between the mother and the child. Different substances can pass from mother to child through the umbilical cord, like alcohol, drugs and even some virusses.

To who does the placenta belong? The mother or the baby?

Explain how the placenta helps in delivering oxygen and nutrients to the baby

What comes out during childbirth?

Childbirth

• Birth of the baby
• Birth of the placenta (this includes the membranes     that held the baby, placenta and the water during the pregnancy).

Actual picture coming up on the next slide.

Membranes = vliezen. We also call this the amniotic sac. This surrounds the foetus and placenta inside of the uterus. Think of it like a big balloon keeping all the water in.

Childbirth

• Birth of the baby
• Birth of the placenta (this includes the membranes     that held the baby, placenta and the water during the pregnancy).

Membranes = vliezen, these surround the foetus and placenta inside of the uterus. Think of them like a big balloon.

Childbirth

4-stage of childbirth:

contractions: amniotic fluid leaks 

out

dilation: cervix become wider

expulsion: rapid contraction push

baby out

afterbirth: placenta chorion and amnion leave

Stage 1+2: contraction & dilation

• This can take a long time (sometimes more than 24 hours!)
• The contractions (which are just muscle cramps of the uterus) slowly start, and increase in strenght slowly. Later on they will also increase in frequency, happening more often.
• The cervix and vagina will widen, slowly making space for the baby 

In Dutch, we call this process 'ontsluiting'

Stage 3: expulsion

• When the dilation phase has widened the cervix far enough, the contractions will get very powerful and rapid.
• This is a sign for the mother to start pushing, and the baby will come out quickly.
• This stage does not take very long, as soon as the head comes out the rest follows fast.

Stage 4: afterbirth

• A little while (minutes) after the expulsion phase, the placenta will be 'born'. We call this the afterbirth.
• Again, contractions come with this. These are not as bad as the contractions of the baby's birth, of course.

And then..?

• When the baby is born, the umbilical cord is cut. This is because now the baby can breathe and eat/drink, so it doesn't need the nutrients via the placenta anymore.
• The end of the umbilical cord will slowly deteriorate and fall off eventually. This then forms the belly button as we know it.
• Fun fact: the differences in belly buttons that we have depend on the person who folds it after birth!

And then..?

• The uterus wil quickly shrink back to its normal size (no bigger than a hand)
• However, the belly muscles and skin will take some more time.
• Due to this, the mother often looks a bit pregnant for a few more weeks.

Difficult births

• Normally, the baby is positioned with its head first.
• However, sometimes the baby is on the wrong side (butt first, feet first, or even completely turned to the side).

Difficult births

• Normally, the baby is positioned with its head first.
• However, sometimes the baby is on the wrong side (butt first, feet first, or even completely turned to the side).
• Another problem that can occur is that the umbilical cord is wrapped around the baby's throat, legs or arms
• This could cut off oxygen supply, which is dangerous.

How to solve that?

• A caesarian section is the way to solve that (keizersnede)
• This involves an operation where the surgeon opens up the uterus and takes the baby out.

What have we learned?

1. What pregnancy is and how a foetus develops in the uterus.
2. How the placenta belongs to the mother and the umbilical cord belongs to the baby.
3. The different phases of childbirth (contractions, dilation, delivery)
4. What is born along with the baby - umbilical cord, amniotic sac and placenta