Article Text

Continuous glucose monitoring improved glycaemic control in pregnant women with diabetes and reduced infant macrosomiaCommentary
  1. Beverley O'Brien
  1. Faculty of Nursing, University of Alberta, Edmonton, Alberta, Canada

Statistics from

H R Murphy

Dr H R Murphy, University of Cambridge, Cambridge, UK; hm386{at}


Does continuous glucose monitoring (CGM) improve glycaemic control in pregnant women with diabetes and reduce infant macrosomia?



randomised controlled trial. Current Controlled Trials ISRCTN84461581.





Follow-up period:

to delivery.


2 diabetes antenatal clinics in the UK.


71 pregnant women (mean age 31 y, mean gestational age 9 wks) who had type 1 diabetes (65% of women) or type 2 diabetes (35%) treated with insulin.


CGM plus standard antenatal care (n = 38) or standard care alone (n = 33). CGM was done every 4–6 weeks until 32 weeks of gestation. A subcutaneous sensor, attached to a portable monitor, was implanted by a nurse into the woman’s hip and worn for 5–7 days. The device recorded average tissue glucose concentrations every 5 minutes, but results were not available until downloaded at the clinic. Standard care included monitoring with a blood glucose meter ⩾7 times/day. At regular clinic visits, patients in both groups reviewed glucose results with the healthcare team and discussed adjustments to diet, exercise, and insulin regimens.


maternal glycaemic control, infant birth weight, and macrosomia (birth weight ⩾90th centile for sex and gestational age).

Patient follow-up:

100% (intention-to-treat analysis). 7 infants were excluded from birthweight analyses because of death or major malformations.


Groups had similar glycaemic control in the first and second trimesters, but differences emerged in the third trimester (table). Mean birth weight was 3340 g in the CGM group and 3630 g in the standard care group (p = 0.07). Median birthweight centile (69 v 93, p = 0.02, adjusted for maternal and infant characteristics) and risk of macrosomia (35% v 60%, {relative risk reduction 41%, 95% CI 2 to 66, number needed to treat 4, CI 3 to 150}*) were lower in the CGM group.

Continuous glucose monitoring (CGM) + standard care v standard care in pregnant women with diabetes


Continuous glucose monitoring improved glycaemic control in pregnant women with diabetes and reduced risk of infant macrosomia.

*Calculated from data in article.


Murphy HR, Rayman G, Lewis K, et al. Effectiveness of continuous glucose monitoring in pregnant women with diabetes: randomised clinical trial. BMJ 2008;337:a1680.

Clinical impact ratings: Endocrinology 6/7; Family/general practice 6/7; General/internal medicine 6/7; Neonatal intensive care 6/7; Obstetric nursing 6/7


To improve birth outcomes in women with pre-existing diabetes, it is critical that glycaemic control be maintained throughout pregnancy. This goal is best accomplished through self-monitoring of preprandial and postprandial blood glucose concentrations ⩾4 times daily.1

Murphy et al hypothesised that CGM, done every 4–6 weeks, would be a powerful tool to facilitate shared decision making through patient education, thereby improving glycaemic control and promoting optimal pregnancy outcomes. Once the sensor was removed, graphs of the effects of eating, activity, and insulin on glucose concentrations could be viewed and discussed by the woman and her provider. The primary outcome, glycaemic control, measured the effectiveness of CGM as an educational tool.

Although the trial had a small sample size, calculated based on a 40% relative reduction in the secondary outcome of macrosomia, it provided sufficient power to detect a 0.5% difference in mean HbA1c concentration. The authors justified the small sample size by suggesting that if the predicted reduction in macrosomia was not sizable, it was unlikely that the costly intervention would be used. Because of some methodological limitations of this trial, the finding that CGM reduces birth weight and macrosomia needs to be confirmed in larger trials.

Commitment to CGM on the part of the woman is essential because she must wear an implanted sensor for ⩽7 days, “keying in” events influencing glucose concentrations. Monitors cannot be disconnected to bathe and often cause skin irritation. Murphy et al noted that women had greater discomfort with CGM during late pregnancy, a critical time for glycaemic control.

Less-intrusive CGM strategies that provide immediate feedback should give community health nurses, obstetrical nurses, and midwives a practical and effective way to facilitate patient education, improve glycaemic control, and avoid adverse pregnancy outcomes in patients with diabetes.


View Abstract


  • Source of funding: Ipswich Diabetes Centre Charity Research Fund; study equipment donated by Medtronic UK.

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