Planning a Pregnancy Planning ahead and taking care of yourself before becoming pregnant is the best thing you can do for you and your baby. Nutrition Before Pregnancy You need about 300 extra calories a day to maintain a healthy pregnancy. These calories should come from a balanced diet of protein, fruits, vegetables, and whole grains. Pregnancy Over Age 30 Many women today are waiting until later in life to have children. In the United States, birth rates for women in their 30s are at the highest levels in three decades. Genetics Genetics is the study of the patterns of inheritance - how traits and characteristics are passed from parents to their children. Types of Genetic Diseases Genetic diseases are classified by type: chromosomal abnormalities, single gene defects, problems caused by exposure to certain substances, or a combination of these. Overview of Birth Defects A "birth defect" is a health problem or physical change that is present in a baby at the time he/she is born. The Difference Between a Chromosome Abnormality and a Single Gene Defect A person can have normal chromosomes in number and structure, but still have a disease or condition caused by a mutation in one or more of the genes on the chromosomes. How Chromosome Abnormalities Happen: Meiosis, Mitosis, Maternal Age, Environment Chromosome abnormalities usually happen as a result of an error in cell division. When to Seek Genetic Counseling A family history of certain diseases or disorders or certain factors affecting the pregnancy itself may be reasons to visit a genetic counselor.