Stillbirth: are we making more progress than we think? A retrospective cohort study.

OBJECTIVE: To quantify how the changing stillbirth risk profile of women is affecting the interpretation of the stillbirth rate. DESIGN: A retrospective, population-based cohort study from 1983 to 2018. SETTING: Victoria, Australia. POPULATION: A total of 2 419 923 births at ≥28 weeks of gestation. METHODS: Changes in maternal characteristics over time were assessed. A multivariable logistic regression model was developed for stillbirth, based on maternal characteristics in 1983-1987, and used to calculate individual predictive probabilities of stillbirth from the regression equation. The number of expected stillbirths per year as a result of the change in maternal demographics was then calculated, assuming no changes in care and in the associations between maternal characteristics and stillbirth over time. MAIN OUTCOME MEASURE: Stillbirth. RESULTS: Compared with 1983-1987, there were more women in older age groups giving birth, more nulliparous women, more indigenous women and women born in Oceania, Asia and Africa, more multiple pregnancies and more women with pre-existing diabetes in 2014-2018. Despite this, the rate of stillbirth fell from 5.42 per 1000 births in 1983 to 1.72 per 1000 births in 2018 (P < 0.001). Applying the multivariable logistic regression equation, derived from the 1983-87 data, to each year, had there been no changes in care or in the associations between maternal characteristics and stillbirth, the rate of stillbirth would have increased by 12%, from 4.94 per 1000 in 1983 to 5.54 per 1000 in 2018, as a result of the change in maternal characteristics. CONCLUSIONS: Population rates of stillbirth are falling faster than is generally appreciated. TWEETABLE ABSTRACT: Population reductions in stillbirth have been underestimated as a result of changing maternal characteristics.

Increasing obstetric intervention for fetal growth restriction is shifting birthweight centiles: a retrospective cohort study.

OBJECTIVE: To assess the impact of increasing obstetric intervention on birthweight centiles. DESIGN: Retrospective cohort study of births in five 2-year epochs: 1983-84, 1993-94, 2003-2004, 2013-2014 and 2016-2017. POPULATION: 665 205 singleton births at ≥32 weeks' gestation. SETTING: All maternity services in Victoria, Australia. METHODS: For each epoch, we calculated the birthweight cutoffs defining each birthweight centile at 34, 37 and 40 weeks' gestation. We calculated rates of iatrogenic delivery over time. We then calculated the number of babies whose birthweight would have classified them as ≥3rd centile based on 1983-84 centile definitions but as <3rd centile based on 2016-2017 centile definitions. MAIN OUTCOME MEASURES: Birthweight centile, and gestation at delivery. RESULTS: From 1983-84 to 2016-2017, the rate of iatrogenic delivery for singleton pregnancies increased at all term gestations: 1.6-6.4% at 37 weeks', 4.5-18.3% at 38 weeks', 7.6-23.9% at 39 weeks' and 18.4-25.1% at 40 weeks' (all P < 0.001). Over the same period, the birthweight cutoffs defining the 3rd, 5th and 10th centiles increased significantly at term, but not preterm, gestations. This led to increasing numbers of term births being classified as small for gestational age (SGA). Of the 2748 babies born in 2016-2017 at 37-39 weeks' gestation with a birthweight <3rd centile in that period, 1478 (53.8%) would have been classified as ≥3rd centile based on 1983-84 centile definitions. CONCLUSION: Increasing intervention is shifting the birthweight cutoffs that define birthweight centiles and thereby redefining what constitutes SGA. This undermines the use of population-derived birthweight centiles to audit clinical care. TWEETABLE ABSTRACT: Increasing obstetric intervention is shifting birthweight centiles and therefore definitions of normality.

Does public reporting of the detection of fetal growth restriction improve clinical outcomes: a retrospective cohort study.

OBJECTIVE: To assess the impact of publicly reporting a statewide fetal growth restriction (FGR) performance indicator. DESIGN: Retrospective cohort study from 2000 to 2017. SETTING: All maternity services in Victoria, Australia. POPULATION: A total of 1 231 415 singleton births at ≥32 weeks of gestation. METHODS: We performed an interrupted time-series analysis to assess the impact of publicly reporting an FGR performance indicator on the rate of detection for severe cases of small for gestational age (SGA). Rates of perinatal mortality and morbidity and obstetric intervention were assessed for severe SGA pregnancies and pregnancies delivered for suspected SGA. MAIN OUTCOME MEASURES: Gestation at delivery, obstetric management and perinatal outcome. RESULTS: The public reporting of a statewide FGR performance indicator was associated with a steeper reduction per quarter in the percentage of severe SGA undelivered by 40 weeks of gestation, from 0.13 to 0.51% (P = 0.001), and a decrease in the stillbirth rate by 3.3 per 1000 births among those babies (P = 0.01). Of babies delivered for suspected SGA, the percentage with birthweights ≥ 10th centile increased from 41.4% (n = 307) in 2000 to 53.3% (n = 1597) in 2017 (P < 0.001). Admissions to a neonatal intensive care unit for babies delivered for suspected SGA but with a birthweight ≥ 10th centile increased from 0.8 to 2.0% (P < 0.001). CONCLUSIONS: The public reporting of an FGR performance indicator has been associated with the improved detection of severe SGA and a decrease in the rate of stillbirth among those babies, but with an increase in the rate of iatrogenic birth for babies with normal growth. TWEETABLE ABSTRACT: The public reporting of hospital performance is associated with a reduction in stillbirth, but also with unintended interventions.