Seasonal and SARS-CoV-2 pandemic changes in the incidence of gestational diabetes.

OBJECTIVE: To test the hypothesis that there is seasonal variation in the rates of gestational diabetes (GDM) diagnosed using a 2-hour oral glucose tolerance test. DESIGN: Monthly assessment of the percentage of women screened from 1 April 2016 to the 31 December 2020 who were diagnosed as having gestational diabetes. SETTING: London teaching hospital. POPULATION: 28 128 women receiving antenatal care between 1 April 2016 and 31 December 2020. METHODS: Retrospective study of prospectively collected data. MAIN OUTCOME MEASURES: Proportion of women screened diagnosed as having gestational diabetes. RESULTS: The mean (SD) percentage of women diagnosed with GDM was 14.78 (2.24) in summer (June, July, August) compared with 11.23 (1.62) in winter (P < 0.001), 12.13 (1.94) in spring (P = 0.002) and 11.88 (2.67) in autumn (P = 0.003). There was a highly significant positive correlation of the percentage testing positive for GDM with the mean maximum monthly temperature (R2  = 0.248, P < 0.001). There was a statistically significant 33.8% increase in the proportion of GDM diagnoses from June 2020 onwards, possibly related to a reduction in exercise secondary to the Covid-19 pandemic. CONCLUSIONS: There is a 23.3% higher rate of GDM diagnoses in the warmer summer months. There has been a 33.8% rise in GDM diagnoses associated with the Covid-19 pandemic. TWEETABLE ABSTRACT: Rates of GDM are higher in summer and since the onset of the Covid-19 pandemic.

Impact of changes to national UK Guidance on testing for gestational diabetes screening during a pandemic: a single-centre observational study.

OBJECTIVE: To examine the differences in detection rate for gestational diabetes (GDM) comparing the methodology recommended by the National Institute for Health and Clinical Excellence (NICE) compared with testing described as appropriate during the Covid-19 pandemic by the Royal College of Obstetricians and Gynaecologists (RCOG). DESIGN: Cohort study of women delivering between 1 January 2016 and 1 July 2020. SETTING: London Teaching Hospital. POPULATION: All women delivering between 1 January 2016 and 13 May 2020 and follow up of women screening negative between 1 April 2020 and 13 May 2020. METHODS: Retrospective study of prospectively collected data. MAIN OUTCOME MEASURES: Detection rate of gestational diabetes. RESULTS: Using the RCOG guidance, the overall rate of women identified as having gestational diabetes fell from 7.7% (1853/24168) to 4.2% (35/831)(P = 0.0003). Of 230 women who tested negative according to the RCOG criteria from 1 April to 13 May but who subsequently had an oral glucose tolerance test, 47 (20.4%) were diagnosed as having gestational diabetes according to the NICE criteria. CONCLUSIONS: In our setting, the RCOG Covid-19 gestational diabetes screening regime failed to detect 47 of 82 (57%) women subsequently identified as gestational diabetics, and therefore cannot be recommended for general use. TWEETABLE ABSTRACT: Screening for GDM using RCOG Covid criteria reduced detection rates.