Jennifer Hutcheon

Fetal growth restriction (FGR) is a significant clinical concern in pregnancy due to its strong associations with morbidity and mortality. Several ultrasonographic fetal growth standards and references are in use; however, many have limited internal and external validity due to methodological flaws. In recent years, three high-quality charts based on large longitudinal cohort studies were published: the National Institute of Child Health and Human Development (NICHD), International Fetal and Newborn Growth Consortium for the 21st Century (INTERGROWTH-21st), and World Health Organization (WHO) charts. We aimed to summarize the evidence on the predictive ability of small for gestational age (SGA) classification by each of these charts for adverse perinatal outcomes, in order to help inform decisions on chart adoption in clinical settings. MEDLINE, Embase, and CINAHL databases were searched for relevant publications. Outcomes of interest included neonatal SGA, neonatal intensive care unit (NICU) admission, and perinatal mortality, among others. Information on composite outcomes was also extracted. When appropriate, meta-analysis using a random-effects model was carried out to produce summary estimates of the DOR, LR+, and LR-. Seventeen publications were eligible for inclusion, involving a total of 56,706 pregnancies. Predictive ability for neonatal SGA of the INTERGROWTH-21st chart was moderate, whether by AC centile (AUCs 0.77-0.87, 10th centile DORs 4.8-27.4) or EFW centile (AUCs 0.55-0.90, 10th centile DORs 2.2-29.2). The NICHD chart appeared to perform similarly, but only two studies were available. Meta-analysis produced pooled DOR estimates of 9.6 and 13.2 for INTERGROWTH-21st 10th centile AC and 10th centile EFW, respectively, although significant heterogeneity between studies was observed. Prediction of other adverse perinatal outcomes by all charts was generally poor (most AUCs ≤ 0.6 and most 10th centile DORs ≤ 5). While these new fetal growth charts may be able to predict small size at birth, they are inadequate for the prediction of adverse outcomes such as NICU admission or mortality. This reinforces the need for FGR screening methods that are not based on fetal size.

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Introduction: Non-invasive prenatal testing (NIPT) is an accurate and safe screening test for detection of Down syndrome, trisomy 18, and trisomy 13, which can be used to reduce the need for invasive diagnostic testing in high-risk women. In November 2015, British Columba (BC) introduced publicly-funded NIPT as a contingent screening test for women at an increased risk of having a trisomic pregnancy. The objective of this research was to quantify the extent to which the introduction of publicly-funded NIPT influenced the utilization of invasive diagnostic testing in BC.Methods: We used linked population-based provincial prenatal biochemistry and cytogenetic laboratories data maintained by the BC Prenatal Genetic Screening Program and Perinatal Services BC. Our study population included all known singleton pregnancies in BC between April 1, 2011 and April 30, 2017 with a positive result from provincially-funded serum integrated prenatal screen (SIPS), integrated prenatal screen (IPS), and quad marker screen (Quad). We divided this timeframe into three periods: period 1 with no NIPT (April 1, 2011-January 31, 2013), period 2 with self-pay NIPT only (February 1, 2013-October 31, 2015), and period 3 with publicly-funded NIPT (November 1, 2015-April 30, 2017). We performed an interrupted time series analysis using log-binomial regression to evaluate the change in use of invasive diagnostic testing after the introduction of self-pay NIPT and publicly-funded NIPT. Models were adjusted for maternal age and self-reported maternal race.Results: Among the 8,649 pregnancies included in the study, the estimated rate of invasive diagnostic testing decreased by 12.7% (95% CI: 0.79 to 0.97) when self-pay NIPT was introduced. With the introduction of publicly-funded NIPT, the estimated rate of invasive diagnostic testing decreased by 47.8% (95% CI: 0.40 to 0.68). The estimated trend of decrease in the rate of invasive diagnostic testing utilization was 1.7% per month (95% CI: 0.98 to 0.99) within the second period with self-pay NIPT.Conclusions: The introduction of publicly-funded NIPT was associated with a significant decrease in the number of invasive diagnostic tests performed in BC among singleton pregnancies screened positive with provincially-funded SIPS, IPS, and Quad. Future cost-consequences studies including detailed healthcare costs would be valuable.

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