📘 Understanding gestational diabetes

Gestational diabetes is a form of diabetes mellitus that appears for the first time in the 2nd or 3rd trimester of pregnancy [1]. Your body produces insulin, but hormones secreted by the placenta partially block its action. When your pancreas cannot produce enough insulin to compensate for this increased resistance, your blood glucose rises above normal values [2].

The process occurs gradually, as the placenta grows and releases increasing amounts of diabetogenic hormones [1]. Factors such as overweight before pregnancy, age over 25 years and family history of type 2 diabetes increase the risk of developing this condition. However, gestational diabetes can occur even in women without obvious risk factors.

Gestational diabetes differs fundamentally from other types by its temporary cause specific to pregnancy [2]. In type 1 diabetes, the immune system destroys insulin-producing cells, and this destruction is permanent. In type 2 diabetes, the body becomes resistant to insulin over several years due to lifestyle and genetic predisposition.

In gestational diabetes, insulin resistance is caused by placental hormones and usually disappears after birth [1]. It is not an autoimmune disease and does not involve destruction of pancreatic beta cells. Treatment is generally necessary only during pregnancy, although the risk of subsequently developing type 2 diabetes remains increased [3].

Before pregnancy, your pancreas produced enough insulin for your body's needs. There were no placental hormones interfering with insulin action. Your body maintained a balance between insulin production and your cells' glucose needs [4].

Pregnancy creates an additional metabolic demand on the body. Placental hormones progressively increase insulin resistance, and the pancreas must double or even triple its insulin production [1]. If this adaptive capacity is exceeded, hyperglycemia occurs, that is gestational diabetes.

Gestational diabetes is by definition a temporary condition, which resolves in most cases after birth [2]. When the placenta is expelled, the hormones responsible for insulin resistance disappear rapidly [1]. Blood glucose usually returns to normal values in the first days after birth.

However, temporary does not mean without long-term consequences. Between 30% and 50% of women with a history of gestational diabetes will develop type 2 diabetes in the next 15-20 years, and the lifetime risk can reach up to 60% [3]. That's why blood glucose monitoring after birth and adopting a healthy lifestyle are essential for type 2 diabetes prevention.

Gestational diabetes most frequently appears in the second trimester, usually between weeks 24 and 28 of pregnancy [2]. This is the period when the placenta reaches a sufficient size to produce significant amounts of diabetogenic hormones. That's why the glucose tolerance test (OGTT) is performed precisely in this interval [3].

In the third trimester, insulin resistance continues to increase, at a slower rate and reaches maximum in weeks 32-36 [1]. Some cases of gestational diabetes are diagnosed later, if standard screening was negative, but risk factors persist and manifest later. Diagnosis of diabetes in the first trimester is actually pre-existing diabetes, not diagnosed before pregnancy.

Gestational diabetes affects between 10% and 14% of pregnancies globally, with variations depending on the population studied and the diagnostic criteria used [5]. Prevalence varies significantly between regions, being higher in the Middle East, North Africa and Southeast Asia [2].

In recent decades, the incidence of gestational diabetes has constantly increased, parallel with the global obesity epidemic [2]. Lifestyle changes, more advanced maternal age and increased obesity prevalence all contribute to this trend. Standardization of IADPSG diagnostic criteria has allowed a more accurate global estimate of this condition [5].

Several hormones secreted by the placenta interfere with insulin action [4]. Human placental lactogen (hPL) is the main culprit, increasing insulin resistance by stimulating lipolysis and free fatty acid release into circulation [1]. Progesterone and estrogen also contribute to reducing tissue sensitivity to insulin.

Cortisol, produced especially by the adrenal glands, also increases in pregnancy and amplifies insulin resistance by activating glucocorticoid receptors [6]. The placenta produces an enzyme that increases local cortisol level. Placental growth hormone and leptin complete this complex hormonal picture, which puts pressure on the pancreas's capacity to secrete insulin [4].

Yes, gestational diabetes can theoretically occur in any pregnancy, including in women without apparent risk factors. However, the risk is significantly higher if you had gestational diabetes in a previous pregnancy [7]. Between 30% and 50% of affected women will develop this condition again in subsequent pregnancies, with higher rates in high-risk populations [8].

Other factors that increase probability include overweight, age over 35 years, family history of type 2 diabetes and polycystic ovary syndrome [3]. The fact that you had a pregnancy without gestational diabetes does not guarantee that the next pregnancies will be the same. Each pregnancy must be monitored individually, and blood glucose testing remains mandatory.

The placenta influences glucose metabolism to ensure a continuous supply of nutrients to the fetus [6]. The fetus depends exclusively on maternal glucose for growth and development, not being able to produce what it needs itself. By increasing the mother's insulin resistance, the placenta directs more glucose to the fetal circulation [4].

This mechanism is an evolutionary adaptation that works perfectly when the maternal pancreas can compensate [6]. The placenta acts as a complex endocrine organ, secreting hormones that reconfigure maternal metabolism. When this reconfiguration exceeds the mother's adaptive capacity, the result is gestational diabetes [1].

After placental expulsion, the hormones responsible for insulin resistance disappear rapidly from circulation [1]. In most cases blood glucose returns to normal in the first hours or days after birth. Treatment with insulin or oral antidiabetics is usually stopped immediately after birth, with blood glucose monitoring [2].

However, it is essential to perform a glucose tolerance test at 6-12 weeks after birth, to confirm problem resolution [3]. The risk of developing type 2 diabetes remains increased long-term, which is why annual long-term control is recommended. Breastfeeding, maintaining normal weight and regular physical activity can significantly reduce the risk of developing type 2 diabetes in a mother with a history of gestational diabetes [9].