First 2 Years: Biosocial Development

Birthweight doubles by month 4 and triples by 1 year
Height typically increases by 10 inches in the first year
- Substantial variation, depending not only on genes and nutrition but also on birthweight; catch-up growth
Compared to themselves
- Growth often expressed in percentile; comparison with previous percentile is important
Failure to thrive
- Many organic conditions, such as allergies, the microbiome, and liver problems, combine with nonorganic factors
Obesity also has many causes

Varies due to biology and social environment
Newborns sleep about 15-17 hours a day
- Primarily active Sleep
Newborns have a high proportion of REM sleep
Sleep problems…
- First born infants typically receive more attention and this may contribute to sleep problems
- Parent reactions to infant sleep shape the baby’s sleep patterns, which in turn affect the parents
Co-Sleeping
- Asian and African mothers worry more about separation
- European and North American mothers worry more about sex
  - Pros…
    - Easier Response Time
    - Less parental exhaustion
    - More convenient for breast-feeding
  - Cons…
    - Higher SID risk

Head-Sparring
- Biological mechanism
- Protects the brain when malnutrition disrupts body growth
- Brain is the last part of the body to be damaged by malnutrition