between 30 and 84%, depending on ethnic background. a second pregnancy within one year of the previous pregnancy has a large likelihood of gdm recurrence. women diagnosed with gestational diabetes have an increased risk of developing diabetes mellitus in the future. the risk is highest in women who needed insulin treatment, had antibodies associated with diabetes (such as antibodies against glutamate decarboxylase, islet cell antibodies and/or insulinoma antigen-2), women with more than two previous pregnancies, and women who were obese (in order of importance). women requiring insulin to manage gestational diabetes have a 50% risk of developing diabetes within the next five years. depending on the population studied, the diagnostic criteria and the length of follow-up, the risk can vary enormously. the risk appears to be highest in the first 5 years, reaching a plateau thereafter. one of the longest studies followed a group of women from boston, massachusetts; half of them developed diabetes after 6 years, and more than 70% had diabetes after 28 years. in a retrospective study in navajo women, the risk of diabetes after gdm was estimated to be 50 to 70% after 11 years. another study found a risk of diabetes after gdm of more than 25% after 15 years. in populations with a low risk for type 2 diabetes, in lean subjects and in women with auto-antibodies, there is a higher rate of women developing type 1 diabetes (lada). children of women with gdm have an increased risk for childhood and adult obesity and an increased risk of glucose intolerance and type 2 diabetes later in life. this risk relates to increased maternal glucose values. it is currently unclear how much genetic susceptibility and environmental factors contribute to this risk, and whether treatment of gdm can influence this outcome. relative benefits and harms of different oral anti-diabetic medications are not yet well understood as of 2017. there are scarce statistical data on the risk of other conditions in women with gdm; in the jerusalem perinatal study, 410 out of 37,962 women were reported to have gdm, and there was a tendency towards more breast and pancreatic cancer, but more research is needed to confirm this finding. research is being conducted to develop a web-based clinical decision support system for gdm prediction using machine learning techniques. results so far demonstrated great potential in clinical practicality for automatic gdm prognosis. complications gdm poses a risk to mother and child. this risk is largely related to uncontrolled blood glucose levels and its consequences. the risk increases with higher blood glucose levels. treatment resulting in better control of these levels can reduce some of the risks of gdm considerably. the two main risks gdm imposes on the baby are growth abnormalities and chemical imbalances after birth, which may require admission to a neonatal intensive care unit. infants born to mothers with gdm are at risk of being both large for gestational age (macrosomic) in unmanaged gdm, and small for gestational age and intrauterine growth retardation in managed gdm. macrosomia in turn increases the risk of instrumental deliveries (e.g. forceps, ventouse and caesarean section) or problems during vaginal delivery (such as shoulder dystocia). macrosomia may affect 12% of normal women compared to 20% of women with gdm. however, the evidence for each of these complications is not equally strong; in the hyperglycemia and adverse pregnancy outcome (hapo) study for example, there was an increased risk for babies to be large but not small for gestational age in women with uncontrolled gdm. in a recent birth cohot study of 5150 deliveries, a research group active at the university of helsinki and helsinki university hospital, finland demonstrated that the mother's gdm is an independent factor that increases the risk of fetal hypoxia, during labour. the study was published in the acta diabetologica in june 2021. another finding was that gdm increased the susceptibility of the fetus to intrapartum hypoxia, regardless of the size of the fetus. the risk of hypoxia and the resulting risk of poor condition in newborn infants was nearly 7-fold in the fetuses of mothers with gdm compared to the fetuses of non-diabetic mothers. furthermore, according to the findings, the risk of needing to perform resuscitation on the newborn after birth was 10-fold. another finding was that gestational diabetes increased the susceptibility of the fetus to intrapartal hypoxia, regardless of the size of the fetus. "the risk of hypoxia and the resulting risk of poor condition in newborn infants was nearly seven-fold in the fetuses of mothers with gestational diabetes compared to the fetuses of non-diabetic mothers," says researcher mikko tarvonen. according to the findings, the risk of needing to perform resuscitation on the newborn was ten-fold.research into complications for gdm is difficult because of the many confounding factors (such as obesity). labelling a woman as having gdm may in itself increase the risk of having an unnecessary caesarean section. neonates born from women with consistently high blood sugar levels are also at an increased risk of low blood glucose (hypoglycemia), jaundice, high red blood cell mass (polycythemia) and low blood calcium (hypocalcemia) and magnesium (hypomagnesemia). untreated gdm also interferes with maturation, causing dysmature babies prone to respiratory distress syndrome due to incomplete lung maturation and impaired surfactant synthesis. unlike pre-gestational diabetes, gestational diabetes has not been clearly shown to be an independent risk factor for birth defects. birth defects usually originate sometime during the first trimester (before the 13th week) of pregnancy, whereas gdm gradually develops and is least pronounced during the first and early second trimester. studies have shown that the offspring of women with gdm are at a higher risk for congenital malformations. a large case-control study found that gestational diabetes was linked with a limited group of birth defects, and that this association was generally limited to women with a higher body mass index (≥ 25 kg/m2). it is difficult to make sure that this is not partially due to the inclusion of women with pre-existent type 2 diabetes who were not diagnosed before pregnancy. because of conflicting studies, it is unclear at the moment whether women with gdm have a higher risk of preeclampsia. in the hapo study, the risk of preeclampsia was between 13% and 37% higher, although not all possible confounding factors were corrected. epidemiology gestational diabetes affects 3–10% of pregnancies, depending on the population studied.