Feasibility of using self-reported ethnicity in pregnancy according to the gestation-related optimal weight classification: a cross-sectional study

Reduction in spontaneous and iatrogenic preterm births in twin pregnancies during COVID-19 lockdown in Melbourne, Australia: a multicenter cohort study

BACKGROUND

Melbourne, Australia, recorded one of the longest and most stringent pandemic lockdowns in 2020, which was associated with an increase in preterm stillbirths among singleton pregnancies. Twin pregnancies may be particularly susceptible to the impacts of pandemic disruptions to maternity care due to their higher background risk of adverse perinatal outcomes.

METHODS

Multicenter retrospective cohort study of all twin pregnancies birthing in public maternity hospitals in Melbourne. Multivariable log-binomial regression models were used to compare perinatal outcomes between a pre-pandemic group to women in whom weeks 20+0 to 40+0 of gestation occurred entirely during one of two lockdown-exposure periods: exposure 1 from 22 March 2020 to 21 March 2021 and exposure 2 from 22 March 2021 to 27 March 2022.

RESULTS

Total preterm births < 37 weeks were significantly lower in exposure 1 compared with the pre-pandemic period (63.1% vs 68.3%; adjusted risk ratio 0.92 95% CI 0.87-0.98, p = 0.01). This was mainly driven by fewer spontaneous preterm births (18.9% vs 20.3%; adjusted risk ratio 0.95 95% CI 0.90-0.99, p = 0.04). There were also lower rates of preterm birth < 34 weeks (19.9% vs 23.0%, adjusted risk ratio 0.93 95% CI 0.89-0.98 p = 0.01) and total iatrogenic births for fetal compromise (13.4% vs 20.4%; adjusted risk ratio 0.94 95% CI 0.89-0.98, p = 0.01). There were fewer special care nursery admissions (38.5% vs 43.4%; adjusted risk ratio 0.91 95% CI 0.87-0.95, p < 0.001) but no significant changes in stillbirth (1.5% vs 1.6%; adjusted risk ratio 1.00 95% CI 0.99-1.01, p = 0.82). Compared with the pre-pandemic period, there were more preterm births < 28 weeks and neonatal intensive care unit admissions in exposure 2.

CONCLUSIONS

Melbourne's first lockdown-exposure period was associated with lower preterm births in twins without significant differences in adverse newborn outcomes. Our findings provide insights into the influences on preterm birth and the optimal timing of delivery for twins.

Temporal validation and updating of a prediction model for the diagnosis of gestational diabetes mellitus

OBJECTIVE

The original Monash gestational diabetes mellitus (GDM) risk prediction in early pregnancy model is internationally externally validated and clinically implemented. We temporally validate and update this model in a contemporary population with a universal screening context and revised diagnostic criteria and ethnicity categories, thereby improving model performance and generalizability.

STUDY DESIGN AND SETTING

The updating dataset comprised of routinely collected health data for singleton pregnancies delivered in Melbourne, Australia from 2016 to 2018. Model predictors included age, body mass index, ethnicity, diabetes family history, GDM history, and poor obstetric outcome history. Model updating methods were recalibration-in-the-large (Model A), intercept and slope re-estimation (Model B), and coefficient revision using logistic regression (Model C1, original ethnicity categories; Model C2, revised ethnicity categories). Analysis included 10-fold cross-validation, assessment of performance measures (c-statistic, calibration-in-the-large, calibration slope, and expected-observed ratio), and a closed-loop testing procedure to compare models' log-likelihood and akaike information criterion scores.

RESULTS

In 26,474 singleton pregnancies (4,756, 18% with GDM), the original model demonstrated reasonable temporal validation (c-statistic = 0.698) but suboptimal calibration (expected-observed ratio = 0.485). Updated model C2 was preferred, with a high c-statistic (0.732) and significantly better performance in closed testing.

CONCLUSION

We demonstrated updating methods to sustain predictive performance in a contemporary population, highlighting the value and versatility of prediction models for guiding risk-stratified GDM care.

Reduced growth velocity from the mid-trimester is associated with placental insufficiency in fetuses born at a normal birthweight

BACKGROUND

Fetal growth restriction (FGR) due to placental insufficiency is a major risk factor for stillbirth. While small-for-gestational-age (SGA; weight < 10th centile) is a commonly used proxy for FGR, detection of FGR among appropriate-for-gestational-age (AGA; weight ≥ 10th centile) fetuses remains an unmet need in clinical care. We aimed to determine whether reduced antenatal growth velocity from the time of routine mid-trimester ultrasound is associated with antenatal, intrapartum and postnatal indicators of placental insufficiency among term AGA infants.

METHODS

Three hundred and five women had biometry measurements recorded from their routine mid-trimester (20-week) ultrasound, at 28 and 36 weeks' gestation, and delivered an AGA infant. Mid-trimester, 28- and 36-week estimated fetal weight (EFW) and abdominal circumference (AC) centiles were calculated. The EFW and AC growth velocities between 20 and 28 weeks, and 20-36 weeks, were examined as predictors of four clinical indicators of placental insufficiency: (i) low 36-week cerebroplacental ratio (CPR; CPR < 5th centile reflects cerebral redistribution-a fetal adaptation to hypoxia), (ii) neonatal acidosis (umbilical artery pH < 7.15) after the hypoxic challenge of labour, (iii) low neonatal body fat percentage (BF%) reflecting reduced nutritional reserve and (iv) placental weight < 10th centile.

RESULTS

Declining 20-36-week fetal growth velocity was associated with all indicators of placental insufficiency. Each one centile reduction in EFW between 20 and 36 weeks increased the odds of cerebral redistribution by 2.5% (odds ratio (OR) = 1.025, P = 0.001), the odds of neonatal acidosis by 2.7% (OR = 1.027, P = 0.002) and the odds of a < 10th centile placenta by 3.0% (OR = 1.030, P < 0.0001). Each one centile reduction in AC between 20 and 36 weeks increased the odds of neonatal acidosis by 3.1% (OR = 1.031, P = 0.0005), the odds of low neonatal BF% by 2.8% (OR = 1.028, P = 0.04) and the odds of placenta < 10th centile by 2.1% (OR = 1.021, P = 0.0004). Falls in EFW or AC of > 30 centiles between 20 and 36 weeks were associated with two-threefold increased relative risks of these indicators of placental insufficiency, while low 20-28-week growth velocities were not.

CONCLUSIONS

Reduced growth velocity between 20 and 36 weeks among AGA fetuses is associated with antenatal, intrapartum and postnatal indicators of placental insufficiency. These fetuses potentially represent an important, under-recognised cohort at increased risk of stillbirth. Encouragingly, this novel fetal assessment would require only one additional ultrasound to current routine care, and adds to the potential benefits of routine 36-week ultrasound.

The predicted clinical workload associated with early post-term surveillance and inductions of labour in south Asian women in a non-tertiary hospital setting

BACKGROUND

Stillbirth increases steeply after 42 weeks gestation; hence, induction of labour (IOL) is recommended after 41 weeks. Recent Victorian data demonstrate that term stillbirth risk rises at an earlier gestation in south Asian mothers (SAM).

AIMS

To determine the impact on a non-tertiary hospital in Melbourne, Australia, if post-dates IOL were recommended one week earlier at 40 + 3 for SAM; and to calculate the proportion of infants with birthweight < 3rd centile that were undelivered by 40 weeks in SAM and non-SAM, as these cases may represent undetected fetal growth restriction.

MATERIALS AND METHODS

Singleton births ≥ 37 weeks during 2017-18 were extracted from the hospital Birthing Outcomes System. Obstetric and neonatal outcomes for pregnancies that birthed after spontaneous onset of labour or IOL were analysed according to gestation and country of birth.

RESULTS

There were 5408 births included, and 24.9% were born to SAM (n = 1345). SAM women had a higher rate of IOL ≥ 37 weeks compared with non-SAM women (42.5% vs 35.0%, P < 0.001). If all SAM accepted an offer of IOL at 40 + 3, there would be an additional 80 term inductions over two years. There was no significant difference in babies < 3rd centile undelivered by 40 weeks in SAM compared with non-SAM (29.6% vs 37.7%, P = 0.42).

CONCLUSIONS

Earlier IOL for post-term SAM would only modestly increase the demand on birthing services, due to pre-existing high rates of IOL. Our current practices appear to capture the majority at highest risk of stillbirth in our SAM population.

A prospective study of placental growth factor in twin pregnancy and development of a dichorionic twin pregnancy specific reference range

OBJECTIVE

To develop a dichorionic twin pregnancy specific reference range for placental growth factor (PlGF), and to compare gestation-specific placental growth factor levels in twin pregnancies later complicated by pre-eclampsia, hypertensive disorder of pregnancy or fetal growth restriction with control pregnancies.

DESIGN

Prospective observational study.

SETTING

Single large tertiary maternity unit in Ireland.

POPULATION OR SAMPLE

Women with a twin pregnancy.

METHODS

Consenting pregnant women, across a variety of gestations, had a single blood sample taken at one time-point only during their pregnancy. The plasma was initially biobanked and PlGF was measured later in batches using the point of care Triage^® PlGF test.

MAIN OUTCOME MEASURES

Development of pre-eclampsia, hypertensive disorder of pregnancy or fetal growth restriction.

RESULTS

Placental growth factor levels in uncomplicated dichorionic twin pregnancies were significantly lower in the women who later developed pre-eclampsia than in the controls at all gestational intervals. In those that later developed any hypertensive disorder of pregnancy, median PlGF was lower only in those recruited before 24 weeks of gestation, whereas in infants with a customised birthweight below the third centile, PlGF was lower only in those sampled after 24 weeks of gestation.

CONCLUSIONS

Placental growth factor levels in twin pregnancy differ significantly between those women with a pregnancy that will later be complicated by pre-eclampsia and those that will not. This difference is present many weeks before clinical signs or symptoms of disease are present. Using cross-sectional values from uncomplicated twin pregnancies, we have developed a dichorionic twin pregnancy specific reference range for PlGF.

TWEETABLE ABSTRACT

Placental growth factor levels in twin pregnancy differ significantly between women that will later develop pre-eclampsia and those that will not.

Prediction of stillbirth: an umbrella review of evaluation of prognostic variables

BACKGROUND

Stillbirth accounts for over 2 million deaths a year worldwide and rates remains stubbornly high. Multivariable prediction models may be key to individualised monitoring, intervention or early birth in pregnancy to prevent stillbirth.

OBJECTIVES

To collate and evaluate systematic reviews of factors associated with stillbirth in order to identify variables relevant to prediction model development.

SEARCH STRATEGY

MEDLINE, Embase, DARE and Cochrane Library databases and reference lists were searched up to November 2019.

SELECTION CRITERIA

We included systematic reviews of association of individual variables with stillbirth without language restriction.

DATA COLLECTION AND ANALYSIS

Abstract screening and data extraction were conducted in duplicate. Methodological quality was assessed using AMSTAR and QUIPS criteria. The evidence supporting association with each variable was graded.

RESULTS

The search identified 1198 citations. Sixty-nine systematic reviews reporting 64 variables were included. The most frequently reported were maternal age (n = 5), body mass index (n = 6) and maternal diabetes (n = 5). Uterine artery Doppler appeared to have the best performance of any single test for stillbirth. The strongest evidence of association was for nulliparity and pre-existing hypertension.

CONCLUSION

We have identified variables relevant to the development of prediction models for stillbirth. Age, parity and prior adverse pregnancy outcomes had a more convincing association than the best performing tests, which were PAPP-A, PlGF and UtAD. The evidence was limited by high heterogeneity and lack of data on intervention bias.

TWEETABLE ABSTRACT

Review shows key predictors for use in developing models predicting stillbirth include age, prior pregnancy outcome and PAPP-A, PLGF and Uterine artery Doppler.

Can risk prediction models help us individualise stillbirth prevention? A systematic review and critical appraisal of published risk models

BACKGROUND

Stillbirth prevention is an international priority - risk prediction models could individualise care and reduce unnecessary intervention, but their use requires evaluation.

OBJECTIVES

To identify risk prediction models for stillbirth, and assess their potential accuracy and clinical benefit in practice.

SEARCH STRATEGY

MEDLINE, Embase, DH-DATA and AMED databases were searched from inception to June 2019 using terms relevant to stillbirth, perinatal mortality and prediction models. The search was compliant with Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines.

SELECTION CRITERIA

Studies developing and/or validating prediction models for risk of stillbirth developed for application during pregnancy.

DATA COLLECTION AND ANALYSIS

Study screening and data extraction were conducted in duplicate, using the CHARMS checklist. Risk of bias was appraised using the PROBAST tool.

RESULTS

The search identified 2751 citations. Fourteen studies reporting development of 69 models were included. Variables consistently included were: ethnicity, body mass index, uterine artery Doppler, pregnancy-associated plasma protein and placental growth factor. For almost all models there were significant concerns about risk of bias. Apparent model performance (i.e. in the development dataset) was highest in models developed for use later in pregnancy and including maternal characteristics, and ultrasound and biochemical variables, but few were internally validated and none were externally validated.

CONCLUSIONS

Almost all models identified were at high risk of bias. There are first-trimester models of possible clinical benefit in early risk stratification; these require validation and clinical evaluation. There were few later pregnancy models but, if validated, these could be most relevant to individualised discussions around timing of birth.

TWEETABLE ABSTRACT

Prediction models using maternal factors, blood tests and ultrasound could individualise stillbirth prevention, but existing models are at high risk of bias.

Stillbirth at term: Does size really matter?

Placental dysfunction has a deleterious influence on fetal size and is associated with higher rates of perinatal morbidity and mortality. This association underpins the strategy of fetal size evaluation as a mechanism to identify placental dysfunction and prevent stillbirth. The optimal method of routine detection of small for gestational age (SGA) remains to be clarified with choices between estimation of symphyseal-fundal height versus routine third-trimester ultrasound, various formulae for fetal weight estimation by ultrasound, and the variable use of national, customized, or international fetal growth references. In addition to these controversies, the strategy for detecting SGA is further undermined by data demonstrating that the relationship between fetal size and adverse outcome weakens significantly with advancing gestation such that near term, the majority of stillbirths and adverse perinatal outcomes occur in normally sized fetuses. The use of maternal serum biochemical and Doppler parameters near term appears to be superior to fetal size in the identification of fetuses compromised by placental dysfunction and at increased risk of damage or demise. Multiparameter models and predictive algorithms using maternal risk factors, and biochemical and Doppler parameters have been developed, but need to be prospectively validated to demonstrate their effectiveness.

Identification of the optimal growth charts for use in a preterm population: An Australian state-wide retrospective cohort study

BACKGROUND

Preterm infants are a group at high risk of having experienced placental insufficiency. It is unclear which growth charts perform best in identifying infants at increased risk of stillbirth and other adverse perinatal outcomes. We compared 2 birthweight charts (population centiles and INTERGROWTH-21st birthweight centiles) and 3 fetal growth charts (INTERGROWTH-21st fetal growth charts, World Health Organization fetal growth charts, and Gestation Related Optimal Weight [GROW] customised growth charts) to identify which chart performed best in identifying infants at increased risk of adverse perinatal outcome in a preterm population.

METHODS AND FINDINGS

We conducted a retrospective cohort study of all preterm infants born at 24.0 to 36.9 weeks gestation in Victoria, Australia, from 2005 to 2015 (28,968 records available for analysis). All above growth charts were applied to the population. Proportions classified as <5th centile and <10th centile by each chart were compared, as were proportions of stillborn infants considered small for gestational age (SGA, <10th centile) by each chart. We then compared the relative performance of non-overlapping SGA cohorts by each chart to our low-risk reference population (infants born appropriate size for gestational age [>10th and <90th centile] by all intrauterine charts [AGAall]) for the following perinatal outcomes: stillbirth, perinatal mortality (stillbirth or neonatal death), Apgar <4 or <7 at 5 minutes, neonatal intensive care unit admissions, suspicion of poor fetal growth leading to expedited delivery, and cesarean section. All intrauterine charts classified a greater proportion of infants as <5th or <10th centile than birthweight charts. The magnitude of the difference between birthweight and fetal charts was greater at more preterm gestations. Of the fetal charts, GROW customised charts classified the greatest number of infants as SGA (22.3%) and the greatest number of stillborn infants as SGA (57%). INTERGROWTH classified almost no additional infants as SGA that were not already considered SGA on GROW or WHO charts; however, those infants classified as SGA by INTERGROWTH had the greatest risk of both stillbirth and total perinatal mortality. GROW customised charts classified a larger proportion of infants as SGA, and these infants were still at increased risk of mortality and adverse perinatal outcomes compared to the AGAall population. Consistent with similar studies in this field, our study was limited in comparing growth charts by the degree of overlap, with many infants classified as SGA by multiple charts. We attempted to overcome this by examining and comparing sub-populations classified as SGA by only 1 growth chart.

CONCLUSIONS

In this study, fetal charts classified greater proportions of preterm and stillborn infants as SGA, which more accurately reflected true fetal growth restriction. Of the intrauterine charts, INTERGROWTH classified the smallest number of preterm infants as SGA, although it identified a particularly high-risk cohort, and GROW customised charts classified the greatest number at increased risk of perinatal mortality.

INTERGROWTH-21st compared with GROW customized centiles in the detection of adverse perinatal outcomes at term

Background: INTERGROWTH-21st charts provide standards for infants born under optimal pregnancy conditions. However, their validity in a general obstetric population is unclear. We aimed to identify whether INTERGROWTH-21st charts, compared with gestation related optimal weight (GROW) charts customized on maternal height, weight, and parity, better identified the at-risk infant.Methods: We performed a retrospective cohort analysis of all term women who gave birth at a single tertiary obstetric center during the period 1994-2016. Routinely collected maternity data was used for analysis. The primary outcome was an Apgar score <7 at 5 min. Secondary outcomes included Apgar score <5 at 5 min, stillbirth or admission to the neonatal intensive care unit (NICU). Populations of newborns were identified as SGA by: (a) INTERGROWTH-21st <10th centile (SGA_IG10th); (b) INTERGROWTH-21st z-score < -1 (SGA_IGzscore); and (c) GROW customized charts <10th (SGA_cust). The subgroups identified by only one chart were also specifically examined. Each SGA group was compared to infants appropriate for gestational age (AGA) on all charts (non-SGA).Results: Data for 71,487 births were available for analysis after exclusion of women with missing height or weight data. Only 3280 (4.6%) newborns were considered SGA_IG10th, with 5878 (8.2%) SGA_IGzscore and 7599 (10.6%) SGA_cust. INTERGROWTH-21st identified only 110 additional infants (0.15%) that were not identified by customized charts; none of these experienced any adverse outcomes. Customized centiles identified a further 4429 (6.2%) SGA infants (SGA_cust-only) that were not identified as SGA_IG10th, and who did demonstrate an increased risk of Apgar score <7 (OR 1.33, 95%CI 1.08-3.28) and stillbirth (OR 2.47, 95%CI 1.41-4.44) compared to the non-SGA infant. Significantly more obese women had infants considered SGA_cust (19.3%) than SGA_IG10th (10.0%) or SGA_IGzscore (9.9%).Conclusions: Amongst our general obstetric study population, the 10th centile of INTERGROWTH-21st identified only 4.6% of infants as SGA and was less likely to identify infants of obese women as SGA. Customized centiles identified almost all SGA-IG infants, including an additional group (SGA_cust-only) at higher risk of stillbirth and adverse outcomes compared with non-SGA infants.