ORIGINAL ARTICLE Obstetric Management in Gestational Diabetes DEBORAH L. CONWAY, MD determining the timing and route of de- livery; ● The optimal modality to predict the ptimizing outcomes for women diately any reduction in the perception presence of fetal macrosomia and ex- with gestational diabetes mellitus of fetal movements. cessive/disproportionate fetal growth O (GDM) and their fetuses requires ● Non-stress testing should be “consid- and the occurrence of shoulder dysto- not only careful metabolic management, ered” after 32 weeks’ gestation in cia and its resulting birth trauma. but also appropriately applied fetal sur- women on insulin and “at or near” term veillance techniques and thoughtful se- in women requiring only dietary man- ANTENATAL FETAL lection of the most advantageous timing agement. SURVEILLANCE — Despite the lack and route of delivery. Whenever possible, ● Biophysical profile testing and Doppler of prospective data in this area, most au- these clinical decisions should be based velocimetry to assess umbilical blood thorities agree that women with GDM on the highest level of evidence available flow “may be considered” in cases of treated with insulin or glyburide, those in and should weigh the likelihood and se- excessive or poor fetal growth, or when poor metabolic control regardless of treat- riousness of both maternal and fetal/ there are comorbid conditions, such as ment modality, and those with comorbid neonatal morbidity. In areas where high- preeclampsia. conditions (such as fetal growth abnor- level evidence is lacking, resources ● Ultrasound should be used to detect fe- malities or hypertension) should undergo should be channeled to designing and im- tal anomalies in women with GDM di- fetal surveillance in the form of non-stress plementing clinical studies to get at good agnosed in the first trimester or with testing, contraction stress testing, or bio- answers. In this review, we examine what fasting glucose levels Ͼ120 mg/dl. physical profile assessments (1,2). Using new information exists in the area of ob- ● Amniocentesis to determine fetal lung treatment with insulin as a marker for in- stetric care of women with GDM since the maturity in preparation for delivery is creased fetal risk makes sense, given the time of the Fourth International Work- not necessary in well-dated pregnan- fact that it is these women, not the ones shop-Conference in 1997 and highlight cies after 38 weeks’ gestation. easily controlled with diet, who are more areas where there remains a need for likely to have unrecognized type 2 diabe- sound evidence on which to base practice Timing and route of delivery: tes, a known risk factor for third trimester guidelines. ● The presence of GDM is not by itself an stillbirth (3). The summary statement from the indication for cesarean delivery. It is unlikely that we will see a ran- 1997 Workshop-Conference remarked ● GDM is not an indication for delivery domized trial specifically addressing the that “the lack of data from controlled clin- before 38 weeks’ gestation in the ab- issue of whether or not women with diet- ical studies on which management rec- sence of evidence of fetal compromise. controlled GDM benefit from additional ommendations can be based was a assessment of fetal well-being beyond prominent theme of discussion regarding daily fetal movement counts. The primary The consensus group lacked suffi- antepartum management of GDM” (1). In reason for this is that the outcomes of in- cient data to draw definitive conclusions the end, consensus was reached in the fol- terest for such a trial (perinatal mortality on the following issues: lowing areas of obstetric management: and long-term neurological morbidities such as cerebral palsy) are relatively rare. Fetal surveillance: ● The need for intensified fetal surveil- For example, to detect a doubling of the ● All women with GDM should monitor lance in women with GDM in good stillbirth rate, an estimated sample size of fetal movements during the last 8–10 control on diet alone; 16,000 women was used (4). weeks of pregnancy and report imme- ● The role of fetal weight estimation in If such evidence is absent, informa- ●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●● tion might be drawn from existing and ongoing studies of GDM that include an From the Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, University of unmonitored arm or cohort. In one small Texas Health Science Center–San Antonio, San Antonio, Texas. Address correspondence and reprint requests to Deborah Conway, Assistant Professor, Director, Diabetes randomized trial looking at treatment and in Pregnancy Program, Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, intensive monitoring versus no treatment University of Texas Health Science Center–San Antonio, 7703 Floyd Curl Dr., San Antonio, TX 78229. and no formal fetal surveillance in women E-mail: [email protected]. with GDM, no stillbirths occurred in the Received for publication 4 April 2006 and accepted in revised form 2 June 2006. 150 women with GDM who had routine This article is based on a presentation at a symposium. The symposium and the publication of this article were made possible by an unrestricted educational grant from LifeScan, Inc., a Johnson & Johnson company. care and no antepartum fetal monitoring Abbreviations: AD-BPD, abdominal diameter–biparietal diameter; EFW, estimated fetal weight; GDM, (5). Casey et al. (6) reported on various gestational diabetes mellitus; HAPO, Hyperglycemia and Adverse Pregnancy Outcome; MFMU, Maternal- outcomes of 874 women with diet- Fetal Medicine Units Network. controlled GDM compared with a large A table elsewhere in this issue shows conventional and Syste`me International (SI) units and conversion factors for many substances. nondiabetic cohort. Women were classi- DOI: 10.2337/dc07-s212 fied as having diet-controlled GDM if © 2007 by the American Diabetes Association. their fasting glucose on the diagnostic 3-h DIABETES CARE, VOLUME 30, SUPPLEMENT 2, JULY 2007 S175 Obstetric management in GDM glucose tolerance test was Ͻ105 mg/dl. and comparable to a nondiabetic control tionally charged facets as devastating neo- Fetal surveillance was not performed in cohort, but a relatively small proportion natal injury, avoidance of unnecessary these women unless another indication of them underwent fetal testing, it could maternal harm, and medicolegal liability. for doing so, such as preeclampsia, was be concluded that antenatal fetal testing To compound the problem, the tools and found. Information regarding the propor- does provide additional benefit to women methods we have at our disposal to pre- tion of the diabetic cohort who did un- with “mild” GDM (i.e., absence of fasting dict the maternal-fetal pairs at highest or dergo fetal surveillance was not provided. hyperglycemia). On the other hand, if lowest risk of adverse outcome lack preci- However, the perinatal mortality rate was treatment of mild GDM results in lower sion, while the personal and professional identical between the two groups at mortality and morbidity, but not to the costs of making an incorrect clinical deci- 6/1,000, including comparable stillbirth level found in the nondiabetic women, it sion remain high. Although some progress rates (5/1,000 in the women with diet- may be that fetal surveillance before 40 has been made since the Fourth Interna- controlled GDM and 4/1,000 in the non- weeks has a place in identifying the preg- tional Workshop-Conference in 1997, diabetic women) (6). Notably, this cohort of nancies at highest risk and preventing ad- much work remains to be done. women with diet-treated GDM may or may verse outcome. At its core, this argument boils down not have been “diet-controlled,” given the The HAPO study is enrolling 25,000 to a diligent and thoughtful weighing of high rate of large-for-gestational-age and women in 10 countries who will undergo maternal and fetal risks: the chance of se- macrosomic infants (35 and 23%, respec- 2-h 75-g glucose tolerance tests. As long vere damage to the mother with GDM tively), but nonetheless experienced still- as the fasting glucose level is Ͻ105 mg/dl from cesarean delivery versus the chance birth rates comparable to a nondiabetic and the 2-h postload value is below 200 of severe damage to her fetus from a population without universal antenatal mg/dl, the results of the glucose tolerance shoulder dystocia event at vaginal deliv- fetal surveillance. Thus, the severity of the test will not be revealed to care providers, ery. Fortunately, both occurrences are disease process as evidenced by the glu- and all women in the cohort will be fol- relatively rare. The risk of brachial plexus cose tolerance test results (i.e., the pres- lowed prospectively for various preg- injury (at least transient) when a macro- ence or absence of fasting hyperglycemia) nancy outcomes. The sample size was somic infant (Ͼ4,000 g) is delivered vag- may be a better indicator of fetal risk and planned to provide sufficient numbers inally by a diabetic woman is ϳ2–5% the need for antepartum fetal testing than across the spectrum of glucose values (10–12). Compiling data from several re- the treatment modality. Women with with the intent to identify thresholds use- ports, Rouse and Owen (16) estimated GDM who have fasting hyperglycemia are ful for predicting morbidity attributable that the mean probability that a brachial more likely to require insulin to control to GDM. For example, it is estimated that plexus injury will persist is 6.7%. There- their glucose levels, but the decision to ϳ400 women in the cohort will have a fore, out of 10,000 vaginal deliveries of add such treatment is more subjective fasting glucose value between 100 and macrosomic infants, ϳ13–33 will result than the glucose tolerance test results. 105 mg/dl (8). A large proportion of these in persistent brachial plexus injury, of Two large multicenter studies are cur- women will not undergo treatment or which roughly three-quarters can expect rently underway to determine the impact tests of fetal well-being.