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Should Glucose sensors and insulin pumps be used in most insulin-requiring diabetic pregnancies? Yes - Glucose sensors and Insulin pumps improve glycemic control.

Consider the case of a 33-year-old teacher who has a toddler in preschool, regularly attends Pilates classes, and is in her second pregnancy. Her privacy is limited, and her lunchtime varies by at least 30 minutes. In her first pregnancy when she used multiple daily injections (MD1) for insulin injection, her hemoglobin Alc at 36 weeks' gestation was 7.2%, and her baby's birth weight was 4,200 g. This time around, she cannot get her fasting blood glucose under 110 mg/dL without experiencing marked hypoglycemia around 3:30 a.m.

In her case, the demonstrated benefits of continuous glucose monitoring (CGM) and an insulin pump (for continuous subHHK cutaneous insulin infusion, or CSII) make this method of insulin adminstration a compelling - and even obvious - choice over MDI. A glucose sensor and insulin pump would improve her glucose control, bring down her HbAlc, and lessen the frequency and severity of hypoglycemic episodes, while better meshing with her lifestyle.

She is far from the only type of patient who would benefit, however. Modern CSII pumps (with Bolus Wizard calculators) have been around for a decade, yet we significantly underutilize them. Many, if not most, insulin-requiring pregnant women are good candidates for glucose sensors and insulin pumps.

CSII improves glucose control by providing "background" changes in insulin dosing to match the complexities of metabolism in pregnancy and CGM (as opposed to self-blood glucose monitoring) improves glucose control by removing the fear of unexpected lows, which is a big issue in my patients, and by warning of impending highs.

Together, today's equipment also improves patients' ability to administer insulin in social and business settings. The equipment is also easily programmable and understandable to women who routinely use electronic devices.

A Cochrane systematic review of CSII vs. MDI in pregnancy published in 2007, unfortunately was not that telling for obstetrics, as only two of the seven available randomized trials were deemed appropriate for meta-analysis. While the mean birth weight was higher in the CSII group, there were no significant differences in macrosomia or any other outcomes, and the reviewers warned they could not draw any conclusions because of the dearth of data. It is important to note, too, that the studies involved '90s-style pumps (Cochrane Database Syst. Rev. 2007 [doi: 10.1002/14651858.CD005542.pub2]).

Fortunately, outside of pregnant populations, we see quite a bit of data on CSII v. MDI. For instance, a 2010 Cochrane systematic review of CSII vs. MDI covering 23 randomized controlled trials of 976 nonpregnant patients with type 1 diabetes found a statistically significant difference in [] favoring CSII (-0.3%), as well as a reduction in severe hypoglycemia and higher quality of life scores (Cochrane Database Syst. Rev. 2010 [doi:10.1002/14651858.CD005103.pub2]).

A randomized, controlled, crossover trial published in 2006 called the 5-Nations Trial similarly showed that CSII treatment in individuals with type 1 diabetes resulted in lower HbAlc, lower mean blood glucose level, less fluctuation in glucose levels, and higher quality of life than MDI (Diabet. Med. 2006;23:141-7). CGM technology is rapidly evolving.

A randomized controlled trial published this year found that patients receiving CGM spent significantly less time in hypoglycemia each day and had a concomitant decrease in HbAlc (again-0.3%, approximately). Normo-glycemia was significantly longer (mean of 17.6 vs. 16 hours per day). The 120 type 1 patients in the study had been randomly assigned to either receive real-time CGM or perform conventional self-monitoring (while wearing a masked CGM device) (Diabetes Care 2011;34:795-800).

Another smaller study of patients with type 1 diabetes or gestational diabetes mellitus being treated with MDI found that nocturnal hypoglycemic events dropped significantly when the patients switched to CGM.

Granted, the false alarms that occur with glucose sensors can be disconcerting, the equipment is expensive, and patients have to enter a series of finger-stick blood sugar readings into the monitor for calibration.

Still, most patients place a value on being able to get real-time blood glucose readings at any time, even when asleep, busy, or distracted.

And they can always temporarily suspend their system - to get ready for bed, for example, or to go to Pilates classes.

I use these tools in less than one-third of my patients with type 1 diabetes, and only rarely in patients with type 2 diabetes or gestational diabetes. There is very little evidence about the efficacy and implications of monitoring. Because of this, and because it is expensive, many payers do not reimburse for continuous glucose monitoring (CGM).

The goals of monitoring and treatment are very different. We monitor in order to guide treatment, to guide further diagnostic testing, to predict outcome, and to understand pathophysiology. But when we consider the value of glucose sensors and insulin pumps, we really need to consider the goals of treatment, which include reducing hyperglycemia without tripping over the threshold into hypoglycemia, and reducing short-and long-term neonatal and maternal complications of diabetes.

We have little data to guide us. A 2007 meta-analysis of randomized controlled trials comparing continuous subcutaneous insulin infusion (CSII) to multiple daily injections (MDI) in pregnant patients - an analysis separate from the Cochrane systematic review of 2007 that Dr. Moore mentions - found no significant differences in glycemic control or pregnancy outcomes. The studies included were published between 1986 and 1993, and since then, there have been no randomized trials comparing CSII and MDI in pregnant women (Am. J. Obstet. Gynecol. 2007;197:447-56).

With respect to CGM, a study reported by Dr. Y. Yogev and his associates in 2003 showed some promise: It compared the daily glycemic profiles reflected by continuous and intermittent blood glucose monitoring in pregnant women with type 1 diabetes, and found that CGM recorded high postprandial blood glucose levels and nocturnal hypoglycemic events that were unrecognized by intermittent monitoring. The question remains, however, whether such information leads to clinical interventions that can improve outcomes (Obstet. Gynecol. 2003;101:633-8). A study published a year later, also by Dr. Yogev, showed that asymptomatic hypoglycemic events were surprisingly common in insulin-and glyburide-treated patients with gestational diabetes mellitus. The findings were eye opening, but we really don't know the significance of such hypoglycemic events.

We take it as a matter of faith that it's bad to be hypoglycemic. In reality we know very little about what's "normal" and "abnormal" in diabetic pregnant women and nondiabetic pregnant women.

In the only randomized controlled trial of CGM during pregnancy, women with type 1 and type 2 diabetes who were early in their pregnancies were assigned to perform self-blood glucose monitoring seven times a day or to have professional CGM for 1-week periods every 4-6 weeks. Findings in both groups were used to adjust therapy. By 36 weeks' gestation, the CGM group had significantly lower Hb[A.sub.1C]. Birth weights and the rate of macrosomia also were reduced (BMJ 2008;337:a1680). The findings were impressive, but some of the data are unusual. For instance, the incidence of large for gestational age (LGA) infants was reduced from 60% to 35%; both of these rates are high compared with rates at other centers. Data from the California Sweet Success program - a statewide effort to collect and share data on diabetes in pregnancy - show LGA in patients with type 1, type 2, and gestational diabetes to be 22.5%, 20%, and 11.4%, respectively - 27% of the type 1 patients were on CSII.

The American Association of Clinical Endocrinologists last year published a consensus statement recommending CGM for patients with type 1 diabetes who have certain risk factors, like frequent hypoglycemia or Hb[] over target. The AACE statement also includes those who are pregnant or about to become pregnant as ideal candidates for CGM, but curiously it provides no data to support this.

We have much more to learn. It is telling that in a recently published evaluation of a closed-loop insulin delivery model (an "artificial pancreas") in pregnant women with type 1 diabetes, investigators concluded that "before outpatient closed-loop studies proceed, they must be supported by scientifically rigorous data on safety and efficacy of real-time CGM," as well as more data on the algorithm for adjusting insulin infusion rates based on glycemic levels seen in pregnancy.

This feature is based on presentations given by Dr. Moore and Dr. Combs at the annual meeting of the Diabetes in Pregnancy Study Group of North America in Washington.

Yes--Glucose sensors and insulin pumps improve glycemic control.

No--There are few data showing improved outcomes

Dr. Moore is professor and chair of reproductive medicine at the University of California, San Diego. He said he had no relevant financial disclosures.

Dr. Combs is with Obstetrix Medical Group in San Jose, Calif. He said he had no relevant financial disclosures.
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Author:Moore, Thomab R; Combs, C.Andrew
Publication:OB GYN News
Date:Aug 1, 2011
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