Rethinking Intrapartum Care
Guidance for tight blood glucose control during labor and delivery for insulin-treated individuals — as reflected in the American College of Obstetricians and Gynecologists Practice Bulletin No. 201 on Pregestational Diabetes and in recommendations from the United Kingdom’s National Institute for Health and Care Excellence (NICE) — is based on small case series and overall “poor-quality” evidence that more recent research has failed to back up, Dr. Bartal said.
A systematic review published in 2018, for example, concluded there is a paucity of high-quality data supporting the association of glucose during labor and delivery with neonatal hypoglycemia in pregnancies complicated by diabetes (Diabet Med. 2018;35:173-83). And in a subsequent retrospective cohort study of pregnant women with type 1/type 2/GDM and their neonates, the same investigators reported no difference in the target glucose in labor between those with and without neonatal hypotension, after adjustment for important neonatal factors such as LGA and preterm delivery (Diabet Med. 2020;37:138-46).
Also exemplifying the body of research, Dr. Bartal said, is another single-center retrospective study published in 2020 that evaluated outcomes in the years before and after the institution of a formal intrapartum insulin regimen (a standardized protocol for titration of insulin and glucose infusions) for women with pregestational or gestational diabetes. The protocol was associated with improved maternal glucose control, but an increased frequency of neonatal hypoglycemia (Obstet Gynecol. 2020;136:411-6).
Her own group at the University of Texas in Houston looked retrospectively at 233 insulin-treated pregnancies complicated by type 2 diabetes and found no significant difference in the rate of neonatal hypoglycemia between those placed on a drip and those who were not, Dr. Bartal said. Over 40% of the newborns had hypoglycemia; it occurred irrespective of the route of delivery as well (J Matern Fetal Neonatal Med. 2022;35:7445-51).
Only two published randomized controlled trials have evaluated blood sugar control in labor, she said. The first, published in 2006, compared a continuous insulin drip with a rotation of glucose and non–glucose-containing fluids in insulin-requiring diabetes and found no differences in maternal blood glucose (the primary outcome) and a similar risk of neonatal hypoglycemia (Am J Obstet Gynecol. 2006;195;1095-9).
The second RCT, published in 2019, evaluated tight versus liberalized control (60-100 mg/dL, checking every hour, versus 60-120 mg/dL, checking every 4 hours) in laboring women with GDM. The first neonatal blood glucose level was similar in both groups, while the mean neonatal blood glucose level in the first 24 hours of life was lower with tight control (54 vs 58 mg/dL, P = .49) (Obstet Gynecol. 2019;133:1171-7). Findings from a new RCT conducted at the University of Texas in Houston of usual care versus more permissive glucose control will be presented at the SMFM Pregnancy Meeting in February 2024, she said.
Neonatal hypoglycemia is associated with increased risk of NICU admission, “but it’s also associated with possible long-term developmental deficit,” Dr. Bartal said, with the risk highest in children exposed to severe, recurrent, or clinically undetected hypoglycemia. Research has documented significantly increased risks of low executive function and visual motor function, for instance, in children who experienced neonatal hypoglycemia.
The risk of neonatal hypoglycemia has been linked to a variety of factors outside of the intrapartum period such as diabetes control and weight gain during pregnancy, neonatal birth weight/LGA, neonatal adiposity, gestational age at delivery, maternal body mass index, smoking, and diabetes control prior to pregnancy, Dr. Bartal noted. Also challenging is the reality that neonatal hypoglycemia as a research outcome is not standardized; definitions have varied across studies.
Tight intrapartum control comes with “costs,” from close monitoring of labor to increased resource utilization, and it may affect the labor experience/satisfaction, Dr. Bartal said. “But furthermore,” she said, “there are studies coming out, especially in the anesthesiology journals, that show there may be possible harm,” such as the risk of maternal and neonatal hyponatremia, and maternal hypoglycemia. A 2016 editorial in Anaesthesia (2016;71:750) describes these concerns, she noted.
“I do think we need to rethink our current recommendations,” she said.
Dr. Durnwald reported serving on the Dexcom GDM advisory board and receiving funding from United Health Group and the Helmsley Charitable Trust. Dr. Bartal and Dr. Rosenn reported no conflicts of interest.