A pregnant woman's diet may not meet her need for folates. A good source of this nutrient is:

Choice A reason: This is not the main reason, as the use of contraceptives for an extended time does not necessarily affect the fertility of a woman. Most contraceptives are reversible and do not cause permanent damage to the reproductive system. However, some contraceptives may take longer to wear off than others, and some may have side effects that can interfere with ovulation or implantation.

Choice B reason: This is the main reason, as the aging process can affect the ovaries and the quality and quantity of the eggs. As a woman ages, her ovarian reserve (the number of eggs in the ovaries) declines, and the eggs become more prone to chromosomal abnormalities. This can reduce the chances of conception and increase the risk of miscarriage or birth defects.

Choice C reason: This is not the main reason, as prepregnancy medical attention is not a prerequisite for achieving pregnancy. However, prepregnancy medical attention can be beneficial for a woman who is older than 35 years, as it can help identify and manage any existing or potential health problems that may affect the pregnancy, such as diabetes, hypertension, or thyroid disorders.

Choice D reason: This is not the main reason, as personal risk behaviors are not specific to a woman who is older than 35 years. Personal risk behaviors are factors that can negatively affect the fertility of any woman, regardless of age. Some examples of personal risk behaviors are smoking, drinking, using drugs, having multiple sexual partners, or having sexually transmitted infections.

Choice A reason: A previous birth of a large infant (macrosomia) is a risk factor for gestational diabetes mellitus (GDM). A large infant may indicate that the mother had high blood glucose levels during pregnancy, which can cause the fetus to grow larger than normal. Women who have had a large infant are more likely to develop GDM in subsequent pregnancies.

Choice B reason: Underweight before pregnancy is not a risk factor for GDM. In fact, being overweight or obese before pregnancy is a risk factor for GDM, as it increases insulin resistance and makes it harder for the body to use glucose effectively.

Choice C reason: A previous diagnosis of type 2 diabetes mellitus is not a risk factor for GDM. It is a contraindication for GDM, as it means that the woman already has diabetes before pregnancy. GDM is a condition that develops during pregnancy and usually resolves after delivery.

Choice D reason: Maternal age younger than 25 years is not a risk factor for GDM. In fact, being older than 25 years is a risk factor for GDM, as it increases the risk of insulin resistance and other metabolic changes that can affect glucose tolerance.