Pregnancy and Birth
A fertilised egg develops over about nine months supported by the placenta.
About this topic
After fertilisation, the zygote divides as it travels to the uterus, and implants in the lining about a week later. The placenta forms, allowing exchange of oxygen, nutrients and waste between mother and foetus without mixing blood, while the amniotic fluid protects the foetus. Birth takes about 40 weeks after conception, and begins with contractions.
The embryo becomes a foetus after about eight weeks, when the main organs have formed. The umbilical cord links the foetus to the placenta, carrying oxygenated blood and nutrients in and waste out. Substances such as alcohol, nicotine, some drugs and viruses like rubella can cross the placenta and harm development, so mothers are advised to avoid them.
Birth has three stages: contractions widen the cervix, the baby is pushed out through the vagina, and the placenta is delivered. Hormones such as oxytocin cause contractions, and the baby then starts to breathe. Breast milk contains antibodies and nutrients ideal for the newborn, and colostrum is the first rich milk. Caesarean section is a surgical alternative when needed.
Antenatal care includes scans, folic acid to prevent spina bifida and healthy habits. A common misconception is that the mother's and baby's blood mix; they are separated by thin membranes, and substances move by diffusion, osmosis and active transport.
Key ideas
- Zygote to embryo to fetus
- The placenta exchanges nutrients and waste
- Labour begins with contractions
Quick check
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Biology underpins medicine, farming, conservation and biotechnology.
Frequently asked questions
What is Pregnancy and Birth?
A fertilised egg develops over about nine months supported by the placenta.
What will I learn in Pregnancy and Birth?
Zygote to embryo to fetus. The placenta exchanges nutrients and waste. Labour begins with contractions.
Is Pregnancy and Birth part of Biology?
Yes. It is one of 150 Biology topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Pregnancy and Birth lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Pregnancy and Birth?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
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