Introducción

In pregestational diabetes (PGD) glycemic control should be strict, with frequent monitoring of glucose levels to adjust treatment as pregnancy progresses¹. Capillary glucose monitoring is the most commonly used method for glucose monitoring and is recommended up to 7 times per day². Continuous glucose monitoring (CGM) is an alternative that measures interstitial glucose³. The sensor contains the enzyme glucose oxidase, which causes interstitial glucose to react with oxygen and the electrons released from this reaction are measured by the sensor in a glucose concentration-dependent manner⁴.

The American Diabetes Association (ADA) and the American College of Obstetrics and Gynecology (ACOG) have established specific goals for pregnant women using CGM.

The use of CGM during pregnancy in Peru is limited. The present case study evaluated the glycemic parameters of CGM in patients with pregestational type 2 diabetes mellitus for 2 weeks during gestation, as well as the impact it had on diabetes management.

Case report

This communication presents four cases of pregnant women over 18 years of age with PGD seen at the endocrinology clinic of the Hospital Nacional Docente Madre Niño San Bartolomé, Lima, Peru. The pregnant women were fitted with a FreeStyle 2 CGM for two weeks and participated in weekly nutrition education videoconferences that included nutrition concepts, carbohydrate counting and daily food intake records. Additionally, they had weekly checkups with their endocrinologist. Insulin was initiated when the time above 140 mg/dL was >20%.

The study was approved by the Hospital Ethics Committee. All participants signed an informed consent form.

Case description

Pregnant 1: 34 years of age, without previous treatment. The CGM was placed at 32 weeks of gestation, insulin detemir was started and the dose was decreased 3 times due to nocturnal hypoglycemia (Figure 1). The outcome was cesarean section at term, with a newborn weighing 4.3 kg.

Figure 1 Report of average glucose and hypoglycemia events in pregnant women 1. 

Pregnant 2: 29 years old, with a history of hypothyroidism, previous treatment with metformin and glibenclamide. During gestation, treatment was started with NPH and regular insulin; the dose was adjusted 2 times prior to the use of the CGM. The CGM was placed at 22 weeks of gestation. The outcome was a 3 kg fetal death at 37 weeks of gestation.

Pregnant 3: 39 years old, previously treated with metformin and glibenclamide, with a history of hypothyroidism. During gestation she was started on NPH and regular insulin and the doses were adjusted 8 times before the CGM. CGM was placed at 8 weeks of gestation. The outcome was a missed abortion at 10 weeks gestation.

Table 1 Glucometric characteristics of continuous monitoring of pregnant women. 

Pregnant 4: 31 years old, previously treated with metformin. The sensor was placed at 17 weeks gestation; the sensor did not calculate the estimated HbA1c. The patient required only dietary management. She was admitted at 39 weeks and 3 days for suspected intrahepatic cholestasis, polyhydramnios and fetal macrosomia. During hospitalization, she developed placental insufficiency and underwent an induced cesarean section, with a newborn weighing 3.9 kg.

Discussion

In our study, the CGM helped to establish glycemic patterns and treatment adjustments. These devices served as positive feedback to patients, who modified their diet by seeing in real time the effect of food on their glucose level. Previous studies have shown how the CGM helps to establish early pharmacological treatment in PGD⁴.

One pregnant woman achieved adequate glycemic control with only nutritional education supported by the use of the sensor (Figure 2). In another patient, insulin dose was reduced due to nocturnal hypoglycemia identified with the CGM, a previously reported finding⁵.

Figure 2 Glucose pattern comparison in pregnant woman 2 and pregnant woman 4. 

Pregnant 2 had a fetal outcome of fetal death; her time in range (TIR) was the lowest of the group (Figure 2). High TIR and low average daily glucose are associated with a lower risk of neonatal complications⁶.

Pregnant woman 3 had uncontrolled diabetes, requiring insulin adjustments prior to the use of the CGM. After sensor placement, the patient maintained adequate glycemic control with a TIR of 92%. It is likely that glycemic dyscontrol prior to sensor use may have contributed to the missed abortion, supporting the need for good glycemic control even at preconception².

The main benefit of CGM is the reduction of maternal-perinatal pathologies such as preeclampsia, macrosomia, cesarean delivery, and preterm delivery^7-9. The CGM has been related to better glycemic control and lower glycemic variability in pregnant women and consequently better outcomes in neonates¹. The pregnant women in this case series reported a better understanding between their dietary intake and postprandial glycemia values.

In conclusion, the CGM is useful for the management of patients with type 2 diabetes mellitus during pregnancy, allowing the identification of glycemic patterns that require early intervention to avoid maternal-neonatal complications.