Biology 12: Pregnancy, Embryo Development and BirthPart A: Fetal Development

*Can you distinguish between different animal embryos? Check out NOVA: Guess the Embryo

-Teratogens are agents causing a birth defect and are usually something in the environment that the mother is exposed to during pregnancy (e.g. prescribed medication, drugs, alcohol or some diseases).

-Once a common blood supply exists between the mother and fetus after implantation, anything in the maternal blood supply can diffuse into the fetal circulation. This occurs about 10 to 14 days after fertilization of the egg.

-As the chart above indicates, there are specific times in which certain organs can be affected by teratogens.

Part B: Female Body Changes with Pregnancy

*View Crash Course: Pregnancy and Development

Part C: Birth

-Labour is induced by a positive feedback loop that involved the hormones estrogen and oxytocin.

-Birth can take place either naturally or by caesarean section, depending on what is best for the health of the mother and baby.

*View Natural Birth Animation

*View Caesarean Animation

*View BBC: Caesarean births ‘affecting human evolution’

Part D: Breast Feeding

-Lactation is unique in mammals and is in response to mechanoreceptors and the hormones prolactin and oxytocin.