What things increase a woman's risk of infertility?

Female fertility is known to decline with:

• Age. Many women are waiting until their 30s and 40s to have children. In fact, about 20% of women in the United States now have their first child after age 35, and this leads to age becoming a growing cause of fertility problems. About one-third of couples in which the woman is older than 35 years have fertility problems. Aging not only decreases a woman's chances of having a baby but also increases her chances of miscarriage and of having a child with a genetic abnormality. 
  

Aging decreases a woman's chances of having a baby in the following ways:

• Her ovaries become less able to release eggs.
• She has a smaller number of eggs left.
• Her eggs are not as healthy.
• She is more likely to have health conditions that can cause fertility problems.
• She is more likely to have a miscarriage.

• Smoking.
• Excessive alcohol use.
• Extreme weight gain or loss.
• Excessive physical or emotional stress that results in amenorrhea (absent periods).

Source
Infertility FAQs
Centers for Disease Control and Prevention  

GeoSalud, August 12, 2013