Prenatal Development

Stage 1: Germination: Approx. 2 weeks

Fertilisation to implantation

2 Gametes join, forming a Zygote (46 chromosomes in 2 pairs)

Week 1 - 100 cells (now a Blastocyst)

Cells arrange in to either:

-skin, hair, nervous system, sensory organs

-digestive and respiratory system

-circulatory and excretory system, muscles

Stage 2: Embryonic: 2-8 weeks

Heart beat at 4 weeks

Brain function

Body structures form

Become reactive to noise

Most susceptible to Teratogens at this stage, but many women won't even know their pregnant

Stage 3: Foetal: 7 months

Bone starts to appear

Month 4-6 is the 'quickening development' as foetus nearly doubles in size

Teratogens are external agents that influence development

Most result in restrictions of oxygen/lack nutrients

Thalidomide: 1960s drug used to alleviate morning sickness. Tested on rats and produced no side effects. Human babies born with serious defects e.g. missing limbs, heart defects. Resulted in low life expectancy. If the drug was taken later on in pregnancy then less defects occurred.

Diet: Severe malnutrition stunts prenatal growth and increased the risk of still births. Scans on still birth babies showed fewer than average brain cells.

Smoking: Increase risk of miscarriage, prenatal death and sudden infant death. Nicotine and carbon monoxide goes in to the foetus's blood stream which impairs functioning of the placenta. This can result in genetic damage (Chica et al 2005)

Alcohol: Results in Foetal Alcohol Syndrome (FAS). More alcohol consumed = more symptoms (Jones et al 1973). Symptoms are malformations of the heart, limb defects, seizures and below average intellegence.

Drugs: 1/3 of cocain exposed babies born prematurely and some show withdrawal symptoms (Ukeje et al 2001)

Chromosomal errors: 3 copies of an autosome, most common known as Down Syndrome. Women age 40 have 1 in 106 chance of giving birth to a child with Down Syndrome. Womed age 45 have a 1 in 30 chance of giving birth to a child with Down Syndrome (Chen 2007)