Carbohydrate counting is an excellent method of meal planning during pregnancy. Carbohydrate is the primary nutrient that affects postprandial (after-meal) blood glucose level; fat and protein have less of an immediate effect. Consuming an adequate and consistent amount of carbohydrate helps to keep blood glucose levels in the recommended target range and is important in promoting a healthy pregnancy outcome. Food sources of carbohydrate include grains, vegetables, fruit, milk, and sweets. Work with your registered dietitian to plan a diet that has the correct amount of carbohydrate for your pregnancy. Generally, 40% to 45% of your total calories should come from carbohydrate, although that amount depends on your individual food needs, preferences, and blood glucose levels. A dietitian can determine the target amounts of carbohydrate you need at each meal and snack throughout the day.
Equally important to learning which foods are sources of carbohydrate is learning how to measure out proper portion sizes—to make sure you’re eating enough but not too much. You will also need to know how to make adjustments in your insulin doses based on the amount of carbohydrate you choose to eat. A typical insulin-to-carbohydrate ratio is 1 unit of fast-acting insulin for each 10–15 grams of carbohydrate consumed. However, this number is individual and can vary throughout your pregnancy. Self-monitoring of your blood glucose levels is key to using carbohydrate counting as a meal planning method while you are pregnant and pumping.
Changing insulin needs. The normal hormone production and weight gain that occur during pregnancy increase insulin resistance, causing a woman’s insulin needs to change during the pregnancy. As the graph “Insulin Requirements During Pregnancy” illustrates, insulin needs during the first several weeks of pregnancy are usually not different from those before conception. However, in the latter part of the first trimester, you may have a higher risk of hypoglycemia because of an increase in sensitivity to insulin, rapid fetal growth, and a reduction in eating associated with morning sickness. Around the 16th week of pregnancy, insulin requirements gradually climb because of increasing insulin resistance (due to weight gain) and increasing levels of hormones, including human placental lactogen (hPL), a form of “growth hormone” for the baby. During the last six months of pregnancy, basal and bolus insulin doses may need to be increased every 7–10 days.
Blood glucose monitoring. To keep tabs on increasing insulin requirements and facilitate adjustments, blood glucose self-monitoring should be done 7–10 times daily. Fasting, premeal, and bedtime blood glucose values can assist in evaluating basal insulin infusion requirements. Checking blood glucose values 1–2 hours after eating can determine the adequacy of your bolus amounts. Many women find that as pregnancy progresses they are up going to the bathroom at least once per night; some take advantage of that time to check their blood glucose. Too-high or too-low blood glucose levels in the middle of the night may signal a need for a basal rate adjustment.
Checking for ketones. In addition to blood glucose monitoring, pregnant women with diabetes are usually advised to do a urine ketone check every morning before eating and additionally if blood glucose is high (above 200 mg/dl) or if they are ill. Ketones are acid substances that collect in the bloodstream when the body is unable to break down glucose properly and begins using fat for energy. If the body cannot get rid of the ketones, they build up and can cause a condition called ketoacidosis. Ketones in the blood during pregnancy are associated with decreased intelligence in the baby. The best approach to preventing and treating ketones is to treat elevated blood glucose levels aggressively, to check for ketones when blood glucose is high, and to promptly use the treatment recommended by your diabetes management team if ketones are present.