Testosterone has a profound effect on the developing brain of a young male
infant. Most guys equate testosterone with muscles and erections, but
don't realize how much it affects that "muscle between their ears",
especially to their expectant male child.
In the last five to ten years, researchers have made one groundbreaking discovery
after another in this area. In 2001 researchers found that fetal
testosterone levels were negatively correlated with eye contact even amount
genders.  The latter study literally "opened the eyes" of the research world
and demonstrated how
testosterone affected how the brain interacts with the world.
Other related traits such as empathy and
lowered social skills were also found to
be linked. 
The importance of this cannot be emphasized enough, because it is so critical to
the health and development of your child. Subsequent studies, for example,
found that (in females) a number of autistic traits correlated with fetal
testosterone.  Finally, in 2009 a team of researchers concluded that fetal
testosterone levels were very likely one of the key contributing factors to
autism.  A young male needs testosterone desperately, but not too much
So what can increase fetal testosterone levels? Smoking is a definite risk
factor and has been shown in animal studies to increase fetal testosterone. 
One study even showed a weak association between autistism and smoking. 
There simply is no reason to expose your child to nicotine and smoke. By
the way, smoking is also a risk factor for ADHD 
and behavior problems  as
my link on Smoking for what it does to adult males as well.)
Low testosterone can be just as devastating for a male infant. Researchers have
found evidence that phthalates, a common family of chemicals in plastics that
lower testosterone  are
linked to effeminizing behavior in boys. (See number 10 in my
link on Child
IQ for more details.) Animal studies have shown nasty effects from
phthalates as well, including permanent reproductive disorders  and a recent
human study showed lowered sperm counts as verification.  In other words,
the damage seems to be permanent.
Even more frightening is the fact that initial studies show a correlation between
phthalate exposure and autism  and schizophrenia. 
What can you do? Tell anyone you know who is pregnant to avoid smoking and plastics
Recommended cooking and drinking materials are glass
and stainless steel whenever possible, especially around children.
1) Infant Behavior and Development, 2002, 25(3):327-335, "Foetal testosterone eye
contact in 12-month-old infants"
2) Hormones and Behavior, May 2007, 51(5):597-604, "Elevated rates of
testosterone-related disorders in women with autism spectrum conditions"
3) Brit J of Psychology, 2009, 100:1-22, "Fetal Testosterone and autistic traits"
5) J Child Psychol Psychiatry, Feb 2005, 46(2):198-210, "Foetal testosterone,
social relationships, and restricted interests in children"
6) Nicotine & Tobacco Research, 2003, 5(3):369-374, "Prenatal nicotine increases
testosterone levels in the fetus and female offspring"
7) Amer J of Epidemiology, 2005, 161(10):916-925, "Risk Factors for Autism:
Perinatal Factors, Parental Psychiatric History, and Socioeconomic Status"
8) Am J Psychiatry, 1996, 153:1138-1142, "Is maternal smoking during pregnancy a
risk factor for attention deficit hyperactivity disorder in children?"
9) PEDIATRICS, Dec 1993, 92(6):815-822, "Maternal Smoking Before and After
Pregnancy: Effects on Behavioral Outcomes in Middle Childhood"
10) Toxicology, 1 June 2006,223(1-2):144-155, "Mechanisms underlying the
anti-androgenic effects of diethylhexyl phthalate in fetal rat testis"
11) Toxicological sciences, 2008, 105:(1)153-65, "A Mixture of Five Phthalate
Esters Inhibits Fetal Testicular Testosterone Production in the Sprague-Dawley
Rat in a Cumulative, Dose-Additive Manner"
12) Neurotoxicology, Sep 2009, 30(5):822-31, Epub 2009 Feb 10, "Associations
between indoor environmental factors and parental-reported autistic spectrum
disorders in children 6-8 years of age"
13) Progress in Neuro-Psychopharmacology and Biological Psychiatry, January 2004
14) J of Environmental Health Perspectives, 2005, "Phthalate Exposure during
Pregnancy and Lower Anogenital Index in Boys: Wider Implications for the General