Fats are important components of your diet during pregnancy, supplying essential fatty acids for fetal growth and neural development as well as enhancing your absorption of certain vitamins. But not all fats are equally healthy.

Fats are composed of building blocks called fatty acids. There are three main types of fatty acids and they’re classified as saturated, monounsaturated or polyunsaturated, based on their chemical make-up. Foods naturally contain a mixture of these fatty acids. Animal products contain mostly saturated fats, while plant-based foods and some seafood predominately contain the healthier monounsaturated and polyunsaturated fats.

Your body’s response to fat depends on the quantity and type of fat you eat. Saturated fats raise LDL cholesterol, the “bad” cholesterol linked to heart disease. Monounsaturated fats, found in olives, avocados and nuts, can help lower your LDL cholesterol. Polyunsaturated fats, found in fish and flax seeds, contain two fatty acids that are essential for your health: omega-3 fatty acids and omega-6. Omega-3 fatty acids are particularly beneficial in pregnancy: they’re required for optimal fetal brain and eye development, and have been associated with lower rates of maternal depression.

There is a fourth type of fat that is artificially manufactured. Trans fats (or trans fatty acids) are formed when liquid oils are heated in the presence of hydrogen, creating solid fats such as hard margarine or shortening. While a small amount of trans fat is found naturally in dairy and beef fat, the majority of trans fats are produced commercially to make foods creamier or enhance their shelf-life. Trans fats are found in vegetable shortenings, some margarines, commercially baked goods, crackers, candies, cookies, snack foods, fast foods, fried foods and other processed foods.

Unfortunately, trans fats are not good for your health. The Institute of Medicine (IOM) reported that eating trans fatty acids raises LDL cholesterol, the “bad” cholesterol which has been linked to coronary heart disease and strokes, and lowers the level of HDL or “good” cholesterol. The IOM recommends we eat as little trans fatty acids as possible.

Different foods and different brands of foods can vary widely in their content of trans fats. Until recently, it was difficult to estimate your intake of these “hidden fats” because they were not labeled on foods. The FDA (Food and Drug Administration) has decided that consumers have a right to be informed about the trans fats in their foods. By 2006, all packaged food products will carry nutritional labels revealing the amount of trans fat per serving. In the meantime, look for the words “partially hydrogenated oil” or “hydrogenated oil” on packaged foods; this will tell you whether trans fats are present. If consumers select foods with lower levels of trans fat, the FDA predicts that 600 to 1200 cases of coronary heart disease and hundreds of deaths will eventually be prevented each year.

Pregnant moms should be aware that trans fat does cross the placenta and has been found in umbilical cord blood. While babies do need healthy omega-3 and omega-6 fatty acids for their development, they do not need trans fatty acids. Additionally, one study of pregnant women reported that diets higher in trans fatty acids may be linked to increased rates of preeclampsia. If you’re pregnant or breastfeeding, it’s best to reduce the amounts of unhealthy fats in your diet. Read nutrition labels carefully to help you select foods low in saturated fat, trans fat and cholesterol.

The following guidelines can help you to make healthy choices:

• Avoid trans fat foods with hydrogenated or partially hydrogenated oils as ingredients. These include cookies, crackers, commercially baked goods, and processed foods, fast foods, and deep-fried chips.
• Limit your intake of saturated fats and high cholesterol foods. Saturated fats are high in meats, poultry skin, butter, whole-milk dairy products (ice cream, cheese, milk), and certain oils (coconut and palm).
• Choose healthier fats including monosaturated fats (olive oil, canola oil) and polyunsaturated fats (corn, safflower, soybean, and sunflower oil). Foods with these nutritious fats include nuts, olives, avocado, flax seed and fish.
• Substitute olive oil and other vegetable oils for butter or margarine whenever you can. Choose foods that are grilled, steamed or baked rather than higher fat options which may be pan-fried, deep-fried, or covered in creamy sauces.
• Include some fish in your diet, which contain omega-3 fatty acids that are important for your baby’s visual and neural development. Take an omega-3 supplement if you are vegetarian or you don’t eat fish or flax seeds. (Also see my response on this web site to the question, “Is it safe to eat fish during pregnancy?”)
• Limit your intake of fats to four servings a day. A typical “serving” size of healthy fats is: 1/8 avocado, 1 teaspoon of olive or canola oil, 8 almonds, 10 peanuts, 1 tablespoon of sesame seeds or 2 teaspoons of tahini.

By including small quantities of healthier fats in your diet you’ll provide an optimal start for your baby, a boost to your mood, and benefits for your long-term health.