Pregnancy is associated with insulin resistance (IR) and hyperinsulinemia that may predispose some women to develop diabetes. Gestational diabetes has been defined as any degree of glucose intolerance with an onset, or first recognition during pregnancy.1 This definition does not exclude the possibility that unrecognized glucose intolerance may have antedated the pregnancy, and so, the term hyperglycemia in pregnancy emerges to be more appropriate as suggested lately by the Endocrine Society. The International Association of Diabetes and Pregnancy Study Groups (IADPSG) classify hyperglycemia first detected during pregnancy as either ‘overt diabetes’ or ‘gestational diabetes mellitus (GDM)’.
In 2013, the World Health Organization (WHO) recommended that hyperglycemia first detected during pregnancy be classified as either ‘diabetes mellitus (DM) in pregnancy’ or ‘GDM’. The prevalence of GDM varies from 1-20%, and is rising worldwide, parallel to the increment in the prevalence of obesity and type 2 diabetes mellitus (T2DM). The amount of GDM varies in direct proportion to the prevalence of T2DM in a given population, or ethnic group.
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A worldwide rising trend in obesity has been reported from 1975 to 2016, affecting females and males alike. In women, the rising obesity has led to an increase in the incidence of gestational diabetes mellitus (GDM) as well as associated pregnancy and perinatal complications. Known non-modifiable risk factors for predisposition to GDM include advanced maternal age, ethnicity, and family history of type 2 diabetes mellitus . Maternal obesity independently contributes to the development of GDM. The Center of Disease Control (CDC) estimates that the incidence of GDM in the United States (US) is about 10%. It is reported to be higher in some countries with rates as high as 17.8–41.9% when using the International Association of Diabetes in Pregnancy Study Groups (IADPSG) GDM criteria.
The American Diabetes Association (ADA) formally classifies GDM as “diabetes first diagnosed in the second or third trimester of pregnancy that is not clearly either preexisting type 1 or type 2 diabetes”. However, the exact threshold for a diagnosis of GDM depends on the criteria used, and so far, there has been a lack of consensus amongst health professionals. It is now advised by the ADA, the World Health Organization (WHO), the International Federation of Gynaecology and Obstetrics, and the Endocrine Society, that the International Association of Diabetes and Pregnancy Study Group (IADPSG) criteria be used in the diagnosis of GDM. The IADPSG criteria were developed based on the results of the Hyperglycemia and Adverse Pregnancy Outcomes (HAPO) Study a large multinational and multicenter study of 23,000 pregnant women. One major finding of the HAPO Study was a continuous risk of adverse maternal and fetal outcomes with increasing maternal glycaemia even below the diagnostic threshold for GDM suggesting that criteria for intervention needed to be adjusted. The IADPSG therefore recommends that all women undergo a fasting plasma glucose (FPG) test at their first prenatal visit (where a reading ≥92 mg/dL is indicative of GDM), and that women with FPG the highest prevalence of GDM at 24.2%, while the lowest prevalence was seen in Africa at 10.5%. Almost 90% of cases of hyperglycemia in pregnancy occurred in low- and middle-income countries, where access to maternal healthcare is limited. Even within-countries, GDM prevalence varies depending on race/ethnicity and socioeconomic status. Aboriginal Australians, Middle Easterners, and Pacific Islanders are the most at-risk groups for GDM. Within the United States, Native Americans, Hispanics, Asians, and African-American women are at a higher risk of GDM than Caucasian women. There is also some evidence that GDM prevalence varies by season, with more diagnoses of GDM in summer than winter.
CAUSES OF GESTATIONAL DIABETES AMONG PREGNANT WOMEN
Pregnant women who can't make enough insulin during late pregnancy develop gestational diabetes. Being overweight or obese is linked to gestational diabetes. Women who are overweight or obese may already have insulin resistance when they become pregnant. Gaining too much weight during pregnancy may also be a factor.
EFFECT OF GESTATIONAL DIABETES ON PREGNANT WOMEN
Poor control of diabetes during pregnancy increases the chances for birth defects and other problems for the pregnancy. It can also cause serious complications for the woman. Proper health care before and during pregnancy can help prevent birth defects and other health problems.
The importance of aiming to understand and effectively treat or prevent GDM is illustrated by the wide-ranging consequences of GDM for both the mother and the fetus. Mother GDM increases the risk of a number of short-term and long-term maternal health issues. In addition to the stress of normal pregnancy, GDM is associated with antenatal depression. There is also an increased risk of additional pregnancy complications, including preterm birth and preeclampsia, and, in many cases, surgical delivery of the baby is required.
RISK FACTORS AS REGARDS GESTATIONAL DIABETES
Epidemiological studies of risk factors for GDM are limited and are typically afflicted by confounding factors. In addition, inconsistencies in diagnostic criteria for GDM and measurements of risk factors make it difficult to compare findings across studies. Despite these concerns, several risk factors for GDM emerge consistently. These include overweight/obesity, excessive gestational weight gain, westernized diet, ethnicity, genetic polymorphisms, advanced maternal age, intrauterine environment (low or high birthweight), family and personal history of GDM, and other diseases of insulin resistance, such as polycystic ovarian syndrome (PCOS). Each of these risk factors are either directly or indirectly associated with impaired β-cell function and/or insulin sensitivity. For example, overweight and obesity are intrinsically linked with prolonged, excessive calorie intake, which overwhelms β-cell insulin production and insulin signaling pathways. Even independently of body mass index (BMI) and overall caloric intake, diet and nutrition are associated with GDM. Diets that are high in saturated fats, refined sugars, and red and processed meats are consistently associated with an increased risk of GDM, while diets high in fiber, micronutrients, and polyunsaturated fats are consistently associated with a reduced risk of GDM. Saturated fats directly interfere with insulin signaling, and they can also induce inflammation and endothelial dysfunction; both pathogenic factors in GDM. On the other hand, n-3 polyunsaturated fatty acids, including those derived from fish and seafood, have anti-inflammatory properties. The relationship between processed meat and GDM remains strong, even after adjustment for fatty acids, cholesterol, heme iron, and protein content. It has been suggested that by-products related to the processing of meat could be responsible such as nitrates (a common preservative in processed meats), or advanced glycation end products (AGEs), which have both been implicated in β-cell toxicity.
TREATMENT FOR GESTATIONAL DIABETES
Treatment for gestational diabetes aims to keep blood glucose levels equal to those of pregnant women who don't have gestational diabetes. The treatment always includes special meal plans and scheduled physical activity, and it may also include daily blood glucose testing and insulin injections.