Gestation and birth

• Fertilisation

  • Can be internal or external
  • The sperm and egg meet in the fallopian tube or the oviduct
• Embryo development

  1. A fertilised ovum divides to form a ball of cells called an embryo

  2. The embryo attaches to the lining of the uterus and begins to develop into a fetus

  3. The fetus becomes a baby when it is born
• It takes about 40 weeks for a fetus to develop in the uterus
• Gestation

  The time it takes for a fetus to develop in the uterus
• What the fetus relies upon its mother for

  • Protection against knock and bumps, and temperature changes
  • Oxygen for respiration
  • Nutrients - food and water
  • Removal of waste substances
• Amniotic fluid


  A liquid that protects the fetus
• Placenta

  • An organ responsible for providing oxygen and nutrients, and removing waste substances
  • It grows into the wall of the uterus and is joined to the fetus by the umbilical cord
• Substances that pass between the mother and fetus

  • Oxygen and nutrients diffuse across the placenta from the mother to the fetus
  • Carbon dioxide and other waste substances diffuse across the placenta from the fetus to the mother
• The blood of the mother and fetus do not mix, but substances diffuse across the placenta
• Other substances that can pass through the placenta include recreational drugs and alcohol
• Drugs can affect the fetus by slowing its growth, reducing the amount of oxygen, and causing bleeding, which can be life-threatening
• Drinking alcohol or smoking while pregnant can increase the risk of stillbirth, premature birth, and long-term health conditions
• Birth

  1. After gestation, the baby is ready to be born

  2. The cervix relaxes and muscles in the wall of the uterus contract

  3. Waves of muscle contractions push the baby out of the mother's body through the vagina

  4. In some cases, a caesarean section is performed if a vaginal birth is not possible for health or medical reasons