Non-standard screening for gestational diabetes

Guidelines recommend screening for GDM using a series of tests that involve several blood samples and consumption of a ‘measured’ glucose drink. Depending on how people are screened, this may involve fasting. Not everyone chooses to complete the ‘recommended’ screening – anecdotally, I supected that this could be much more common in midwifery care.

For this study, I compared ‘non-standard GDM screening’ to ‘recommended screening’ among midwifery clients and physician in BC. I wanted to understand, first, whether the incidence of non-standard screening was more common in midwifery care, and second, what this might mean for infant and maternal health.

A version of this work is being presented as a poster at the UBC Pharmaceutical Sciences Graduate Research Forum on May 4, 2023. The abstract is below – and the full poster is also available here: Poster download

Perinatal Outcomes after Non-standard Screening for Gestational Diabetes Among Midwifery Clients in British Columbia, Canada

Presenter: Elizabeth Nethery

Elizabeth Nethery1,2, Laura Schummers1, Luba Butska2, Michelle Turner2, Jennifer A Hutcheon3,4, Patricia A Janssen3


Midwife-led care may be associated with lower completion of guideline-based prenatal tests and procedures. Routine gestational diabetes mellitus (GDM) screening, using guideline-based methods, is recommended from 24-28 weeks gestation, as diagnosis and treatment can reduce risks of adverse outcomes.1 Qualitative data suggests non-standard screening is more common among midwifery vs physician care.2,3 Rates of non-standard screening are not well understood. We evaluated risks of adverse maternal and neonatal outcomes comparing those unscreened to screened negative for GDM among midwifery clients.


We used a population-based linked cohort of all singleton births (>28 weeks gestational age) from 2005-2019. GDM screening status was obtained from billings data via a validated method.4 We reported frequency of non-standard screening (no screening or no guideline-based screening) compared to screening negative for GDM, crude and adjusted relative risks (RRs) for maternal and perinatal outcomes, adjusted for confounders, among midwifery clients. Potential confounders for adjustment (age, parity, pre-pregnancy body mass, antepartum risk composite, gestational age, health region, scheduled cesarean birth, planned home birth) were selected based on directed acyclic graph approach and informed by previous literature.


Among 91,317 births (2005-2019), 33% of midwifery clients had non-standard gestational diabetes screening. Non-standard screening for GDM was associated with decreased risks compared to those who screened negative for cesarean delivery (RR 0.87, 95%CI 0.84-0.89), shoulder dystocia (RR 0.83, 95%CI 0.77-0.90), large for gestational age (RR 0.88, 95%CI 0.85-0.91) or neonatal hypoglycemia (RR 0.78, 95%CI 0.65-0.92). There was an increased risk of small for gestational age (RR 1.12, 95%CI 1.05-1.19).


Within the context of a midwife-led model of care, non-standard GDM screening (no screening or alternative screening) was not associated with a higher risk of adverse perinatal outcomes normally associated with untreated gestational diabetes; however, an increase in small for gestational age warrants further study.

1.         Feig, D. S. et al. Diabetes Canada Clinical Practice Guidelines Expert Committee. Can. J. Diabetes 42, S255–S282 (2018).

2.         Murray-Davis, B. et al. A framework for understanding how midwives perceive and provide care management for pregnancies complicated by gestational diabetes or hypertensive disorders of pregnancy. Midwifery 115, 103498 (2022).

3.         Stoll, K., Wang, J. J., Niles, P., Wells, L. & Vedam, S. I felt so much conflict instead of joy: an analysis of open-ended comments from people in British Columbia who declined care recommendations during pregnancy and childbirth. Reprod. Health 18, 79 (2021).

4.         Nethery, E., Hutcheon, J. A., Law, M. R. & Janssen, P. A. Validation of Insurance Billing Codes for Monitoring Antenatal Screening. Epidemiology 34, (2023).