Current Management of Gestational Diabetes Mellitus

Guido Menato; Simona Bo; Anna Signorile; Marie-Laure Gallo; Ilenia Cotrino; Chiara Botto Poala; Marco Massobrio


Expert Rev of Obstet Gynecol. 2008;3(1):73-91. 

In This Article

Timing & Route of Delivery

The complication that is the hallmark of GDM is macrosomia, defined as an infant's weight higher than 4000 g.[91] A study defined macrosomia as a body heavier than 4500 g and it found a macrosomia prevalence of 14% in mothers with GDM and 6.3% in a control group without GDM (p = 0.049).[92] In another large, retrospective study, 23% of infants born from GDM mothers weighed more than 4000 g, compared with 8% of infants born from nondiabetic women (p < 0.001).[93]

Some obstetric complications such as prolonged labor, labor augmentation with oxytocin, cesarean delivery, postpartum hemorrhage, third- and fourth-degree laceration, and infection occur more frequently in macrosomic infants than in normal weight infants.[94] Shoulder dystocia is a complication associated with macrosomia.[91] In a study this complication occurred in 31% of neonates weighing more than 4000 g who were delivered vaginally by mothers with diabetes of any type.[95] A study found a 3% prevalence in GDM women, versus 1% in normoglycemic women (p < 0.001).[96] Clinical estimation of fetal size through ultrasonography is used to detect fetal macrosomia, which can be identified by increased abdominal circumference.[15] The 13% error rate (± 2 SD) in estimating fetal weight through ultrasonography should be considered.[97] A recent cost-effectiveness analysis showed that overall expectant management is the preferable approach, irrespective of estimated fetal weight.[98] Some studies recommend a cesarean delivery for GDM women with an estimated fetal weight higher than 4500 g.[37] When the estimated weight is 4000-4500 g, additional factors such as the patient's past delivery history, clinical pelvimetry and the progress of labor may be helpful to determine the appropriate mode of delivery.[37]

There are no indications to pursue delivery before 40 weeks of gestation in patients with good glycemic control, unless other maternal or fetal indications are present.[37] In a study in which insulin-treated GDM women with not macrosomic fetus were randomized to labor induction at 38 weeks of gestation, there was no difference in cesarean delivery rates. However, the induction group delivered a lower proportion of large-for-gestational-age babies.[99] Some authors recommend labor induction at approximately 38 to 39 weeks in insulin-treated GDM patients, since it lowered the shoulder dystocia risk from 10 to 1.4%.[100] A recent Cochrane Database meta-analysis, however, found a similar percentage of shoulder dystocia between the induction groups and the expectant management groups.[101] Compared with those undergoing expectant management, women who underwent labor induction at 38 weeks had no increase in cesarean deliveries.[102] However, a significant difference was found between the GDM and normoglycemic groups in percentage of labor induction (38.6 vs 10.8%; p < 0.001) and caesarean delivery (34 vs 20%; p < 0.001).[103]

When comparing diet and/or insulin with no treatment, the treated group showed a significant reduction in macrosomic babies (Relative risk [RR]: 0.27; confidence interval [CI]: 0.09-0.76) in addition to the aforementioned reduction in neonatal hypoglycemia (RR: 0.13; CI: 0.02-0.97). There was no observed difference in the number of cesarean deliveries (RR: 0.82; CI: 0.36-1.84) or in the number of admissions to the neonatal intensive care unit (RR: 0.57; CI: 0.18-1.86).[4] Treatment of GDM did not reduce perinatal mortality[104] or pre-eclampsia incidence.[105] A study shows that third-trimester amniocentesis for measuring amniotic fluid insulin is safe and well accepted by patients with GDM: so this method could be used to identify those pregnancies with fetal hyperinsulinism.[108] Identification of the hyperinsulinemic fetus before delivery might allow the intensification of maternal insulin therapy, leading to a reduction in incidence and severity of diabetic fetopathy, because hypoglycemia requiring treatment was significantly more common in the macrosomic hyperinsulinemic neonates compared with normoinsulinemic neonates.[109] Amniocentesis for assessment of fetal lung maturity is not indicated in well-controlled patients who have indications for induction of labor or cesarean section as long as there is reasonable certainty about the estimation of gestational age. When delivery is necessary at an early gestational age for the well-being of mother or fetus, delivery should be affected without regard to lung maturity testing.[14]


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