A family history is a record of medical information about an individual and their biological family. Human genetic data is becoming more prevalent and easy to obtain. Increasingly, this data is being used to identify individuals who are at increased risk for developing genetic disorders that run in families.

A chromosomal abnormality in one or both parents increases the risk, even if the affected parent is healthy and has no physical sign of the abnormality. Doctors suspect such an abnormality when couples have had several miscarriages, problems with infertility, or a baby with a birth defect.

This term refers to a woman who gives birth at the age of 35 years or older. The fetus of a woman of advanced maternal age may be at increased risk of genetic changes ( mutations ). The mother is also at risk of health complications during the pregnancy and birth.

A man who is age 40 years or older at the time of conception. (There is no universally accepted definition of advanced paternal age but this criterion is often used in genetic counseling.) Advanced paternal age is associated with an increased risk of new mutations in the offspring

The risk of having a baby with a birth defect greatly increases if you're unable to control your blood sugar levels. Even if your diabetes is well-controlled, your baby is 3 times more at risk of having major birth defect. If you do not have diabetes but develop high blood sugar levels during pregnancy (gestational diabetes) your baby is not at risk of having a major birth defect.

We do not know why an obese woman is at a greater chance of having a baby with a birth defect. The risk to your baby increases as your increases body mass index (BMI) increases. BMI is calculated according to the following formula: your weight in kilograms divided by your height in metres; then, this sum is divided by 2. If you're obese, you're chances of having a child with a neural tube defect (NTD), such as spina bifida is double than that of a non-obese woman. You also have a small but increased risk for having a baby with a heart defect or cleft palate. Obesity during pregnancy can contribute to the childhood – adolescent – adult obesity cycle.

Alcohol affects an unborn baby's development. If you're pregnant or breastfeeding your safest choice is to drink no alcohol at all. Your baby is vulnerable throughout your pregnancy. Any reduction in alcohol consumption at any stage of pregnancy is good. Alcohol exposure during pregnancy increases the risk of major birth defects which include: brain damage; heart defects; and eye defects. Many things will influence the effects that alcohol will have on a baby, including: the quantity of alcohol consumed; the time period over which the alcohol was consumed; your genetic make-up and your ability to digest alcohol; your baby's genetic make-up and their ability to digest alcohol; and if your eating well or has any deficiencies. About 1% of all births in Canada and the United States are affected by fetal alcohol spectrum disorder (FASD). People with fetal alcohol spectrum disorder are not always diagnosed. Diagnosing fetal alcohol spectrum disorder early means people with this disorder can get help to reach their full potential.

Exposure to mercury during pregnancy can affect a baby’s brain development. A fetus is much more sensitive to mercury than an adult.