Poster Presentation International Association of the Diabetes and Pregnancy Study Groups 2022 - Hosted by ADIPS

Flash Glucose Monitoring – Heralding Impaired Placental Flows with Glucometric Lows (#101)

Su Win Htike 1 2 3 , Jenny Wright 1 , Tang Wong 1 2 3 , Angela Lee 1 4 5 , Sarah Abdo 1 3 , Jeff Flack 1 2 3
  1. Department of Diabetes and Endocrinology, Bankstown-Lidcombe Hospital , Sydney, NSW, Australia
  2. Faculty of Medicine, University of New South Wales, Sydney, NSW, Australia
  3. School of Medicine, Western Sydney University, Sydney, NSW, Australia
  4. Department of Diabetes and Endocrinology, Royal Prince Alfred Hospital, Sydney, NSW, Australia
  5. Faculty of Medicine, University of Sydney, Sydney, NSW, Australia

Insulin resistance is a key feature in pregnancy for women with gestational or pre-existing diabetes1. Insulin requirements steadily increase throughout the second and third trimesters2. Falling insulin requirements (FIR) and/or hypoglycaemia after the first trimester is considered an early indicator of placental insufficiency3. We present a case of flash glucose monitoring (FGM) detected hypoglycaemia heralding placental insufficiency in a Type 1 diabetes (T1D) pregnancy.

TT, a 24-year gravida 1 parity 0 woman, presented at 6-weeks’ gestation, with an unplanned pregnancy and suboptimal glycaemic management (HbA1c 9.1%). T1D was diagnosed at age 5 and managed with insulin glargine and aspart at mealtimes. Significant background history included a developmental delay.

At initial review, FGM was commenced, and she was transitioned to detemir and mealtimes insulin aspart. Glycaemic management was challenging due to cognitive impairment, limited health literacy and social supports. Low dose aspirin was started, and she developed gestational hypertension in the second trimester requiring labetalol therapy.

Ultrasonographic examination at 33-weeks demonstrated polyhydramnios with accelerated anthropometric growth with both estimated fetal weight and abdominal circumference >90th percentile.

At 35-weeks, she had increasing time below range (TBR), rising from 9% to 35% on FGM whilst insulin requirements decreased by 29% over a 4 week period. She was admitted for suspected fetoplacental compromise. Her BP was increased at 132/100 mmHg. A feto-maternal unit assessment showed abnormal umbilical and middle cerebral arterial flows and in the context of non-reassuring cardiotocography, she was delivered via emergency caesarean section. A male 3.36kg fetus, Apgar scores 8, 9, 9 was admitted to the special care nursery and received treatment for neonatal hypoglycaemia and jaundice. The placenta histology report later confirmed focal chronic villitis and villous stromal vascular karyorrhexis suggestive of low grade fetal vascular malperfusion.

FIR of ≥15% from the peak daily dose after 20 weeks’ gestation are associated with an increased risk of complications related to placental dysfunction (pre-eclampsia, small for gestational age, stillbirth, prematurity, and placental abruption)4,5. Evidence guiding the management of patients with FIR is limited, leading to varied clinical interventions6. Unlike traditional blood glucose monitoring, which looks only a few points in time, continuous glucose monitoring (CGM) or FGM provides a comprehensive data that track 24 hours. Increased use of CGM or FGM in pregnancies affected by T1D, may assist clinicians in detecting and quantifying the proportion of time glucose levels are below targets and provides a useful indirect indicator of fetoplacental compromise.

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  1. Søholm et al, Falling Insulin Requirement in Pregnant Women With Diabetes Delivering Preterm: Prevalence, Predictors, and Consequences, The Journal of Clinical Endocrinology & Metabolism, Volume 107, Issue 6, June 2022, Pages e2237–e2244, https://doi.org/10.1210/clinem/dgac159
  2. Padmanabhan S et al, Effect of pregnancy on insulin requirements differs between type 1 and type 2 diabetes: A cohort study of 222 pregnancies. Aust N Z J Obstet Gynaecol. 2016 Aug;56(4):352-7. doi: 10.1111/ajo.12446. Epub 2016 Feb 8. PMID: 26852894.
  3. Wilkinson et al, Declining Insulin Requirements in Late Pregnancy: A Cause for Concern? [07D], Obstetrics & Gynecology: May 2020 - Volume 135 - Issue - p 40S, https//doi: 10.1097/01.AOG.0000663396.88371.08
  4. Padmanabhan et al, The Association of Falling Insulin Requirements with Maternal Biomarkers and Placental Dysfunction: A Prospective Study of Women With Pre-existing Diabetes in Pregnancy. Diabetes Care 1 October 2017; 40 (10): 1323–1330. https://doi.org/10.2337/dc17-0391
  5. Pihelgas et al, Decreasing Insulin Requirements in Pregnancy with Pre-existing or gestational Diabetes: management Practices Across Canada, Journal of Obstetrics and Gynaecology Canada, Volume 43, Issue 10, P1180-1183.E1, October 01, 2021. https//doi.org/10.1016/j/jogc.2020.12.015
  6. Prior et al, Implications of Decreasing Insulin Requirements for Diabetes in Pregnancy: A Systematic Review [15D], Obstetrics & Gynecology: May 2020 - Volume 135 - Issue - p 42S. https//doi: 10.1097/01.AOG.0000663544.70437.d8