It is estimated that 10% of all birth defects are caused by a prenatal exposure to a [ Select ] ["teratogen", "toxin", "risk factor"] , which is defined as any environmental factor that can put the baby's development at risk. How much damage might result from exposure depends on the [ Select ] ["timing and amount of the exposure", "the health status of the father", "the age of the mother"] and whether the fetus is male or female ( [ Select ] ["females", "males"] experience more damage). One example is [ Select ] ["sexually transmitted diseases", "alcohol", "tobacco"] , which may lead to neurocognitive and behavioral difficulties in the child, especially if consumed during the [ Select ] ["ninth", "first", "second"] month of prenatal development. Another example is [ Select ] ["drugs", "environmental chemicals", "tobacco"] , which reduces the blood oxygen levels to the fetus and may result in low birth weight, birth defects, and even sudden infant death syndrome. One final example is [ Select ] ["maternal diseases", "environmental chemicals", "maternal stress"] which threatens the homeostasis of the organism and can lead to preterm birth and low birth weight. And it has been correlated with changes to the child's [ Select ] ["brain", "intelligence", "emotional regulation"] (putting them at risk for things like behavioral problems, learning disorders, anxiety, etc.), as well as correlated with a variety of immune and metabolic disorders. The best way to improve maternal outcomes for both mother and baby is to stay away from toxic substances, eat a healthy diet, and exercise regularly. Next