So what exactly causes asthma anyway? The truth is scientists still don't know for sure. Yet a growing stack of evidence suggests events that occur before birth, or just after birth, may increase the risk of your baby getting asthma.

Thus, according to various studies, the following are now believed to cause asthma (Learn more by clicking on the links provided):

1.  Cleanliness:  The hygiene hypothesis and microflora hypothesis both propose lack of exposure to bacteria may set off an immune response that causes asthma.  This is especially true in the first year of life when the immune system is developing.   

2. Antibiotics: Kids who received even one dose of antibiotics before 6 months were 40 percent more likely to develop asthma and allergies. The theory here is antibiotics wipe out bacteria that are needed to help the immune system develop. (I wrote more about this here.  Also, to learn what bacteria have to do with causing asthma, click here and here for a quick refresher)

3. Cesarean sections may cause asthma: A study showed that children born by C-Section are 80 percent more likely to develop asthma. The theory here is these kids are not exposed to bacteria that kids born vaginally are exposed to. (for more click here)

4. Slow growth in utero: Fetus's that are slow growing late in pregnancy when the lungs are developing are 27 percent more likely to develop asthma later in life. The theory here is lungs that develop more slowly may be narrower and more prone to be susceptible to irritants that might result in airway hypersensitivity and therefore narrowed airways (or asthma).

A more recent study at the University of Aberdeen found that a fetus that's 10 percent smaller than average at 10 weeks gestation and stayed small during the pregnancy was five times more likely to develop asthma. 

5. Premature birth: Kids born prematurely at weights of 2.2 pounds had a 21 percent chance of developing asthma, compared to a 9 percent risk for those born a normal weight. The theory here is the inability of the lungs and immune systems to develop properly.

6. Not breast feeding: Children breast fed at least six months had a reduced risk for developing asthma. The theory here is these children are exposed to maternal bacteria needed for the immune system to develop properly. Other studies, however (like this) show breastfeeding might actually cause allergies.

7. Smoke inhalation: Infants exposed to cigarette smoke before birth and after birth had almost a 50 percent increased risk for developing asthma and allergies by the age of four. Smoke exposure in early childhood also increases the risk for allergies, in some cases as much as 50 percent over kids not exposed to second-hand smoke.

This is a sure sign that chemicals inhaled by mom before birth, and passive smoking after birth, can damage the immune system and the lungs of babies.