Induction of labor and cesarean birth in lower-risk nulliparous women at term: A retrospective cohort study

OBJECTIVE

To evaluate whether induction of labor (IOL) is associated with cesarean birth (CB) and perinatal mortality in uncomplicated first births at term compared with expectant management outside the confines of a randomized controlled trial.

METHODS

Population-based retrospective cohort study of all births in Victoria, Australia, from 2010 to 2018 (n = 640,191). Preliminary analysis compared IOL at 37 weeks with expectant management at that gestational age and beyond for uncomplicated pregnancies. Similar comparisons were made for IOL at 38, 39, 40, and 41 weeks of gestation and expectant management. The primary analysis repeated these comparisons, limiting the population to nulliparous women with uncomplicated pregnancies and excluding those with a medical indication for IOL. We compared perinatal mortality between groups using Chi-square tests and multivariable logistic regression for all other comparisons. Adjusted odds ratios and 99% confidence intervals were reported. p < 0.01 denoted statistical significance.

RESULTS

Among nulliparous, uncomplicated pregnancies at ≥37 weeks of gestation in Victoria, IOL increased from 24.6% in 2010 to 30.0% in 2018 (p < 0.001). In contrast to the preliminary analysis, the primary analysis showed that IOL in lower-risk nulliparous women was associated with increased odds of CB when performed at 38 (aOR 1.23(1.13-1.32)), 39 (aOR 1.31(1.23-1.40)), 40 (aOR 1.42(1.35-1.50)), and 41 weeks of gestation (aOR 1.43(1.35-1.51)). Perinatal mortality was rare in both groups and non-significantly lower in the induced group at most gestations.

DISCUSSION

For lower-risk nulliparous women, the odds of CB increased with IOL from 38 weeks of gestation, along with decreased odds of perinatal mortality at 41 weeks only.

Objective measures of smoking and caffeine intake and the risk of adverse pregnancy outcomes

BACKGROUND

In pregnancy, women are encouraged to cease smoking and limit caffeine intake. We employed objective definitions of smoking and caffeine exposure to assess their association with adverse outcomes.

METHODS

We conducted a case cohort study within the Pregnancy Outcome Prediction study to analyse maternal serum metabolomics in samples from 12, 20, 28 and 36 weeks of gestational age. Objective smoking status was defined based on detectable cotinine levels at each time point and objective caffeine exposure was based on tertiles of paraxanthine levels at each time point. We used logistic and linear regression to examine the association between cotinine, paraxanthine and the risk of pre-eclampsia, spontaneous pre-term birth (sPTB), fetal growth restriction (FGR), gestational diabetes mellitus and birthweight.

RESULTS

There were 914 and 915 women in the smoking and caffeine analyses, respectively. Compared with no exposure to smoking, consistent exposure to smoking was associated with an increased risk of sPTB [adjusted odds ratio (aOR) = 2.58, 95% CI: 1.14 to 5.85)] and FGR (aOR = 4.07, 95% CI: 2.14 to 7.74) and lower birthweight (β = -387 g, 95% CI: -622 g to -153 g). On univariate analysis, consistently high levels of paraxanthine were associated with an increased risk of FGR but that association attenuated when adjusting for maternal characteristics and objective-but not self-reported-smoking status.

CONCLUSIONS

Based on objective data, consistent exposure to smoking throughout pregnancy was strongly associated with sPTB and FGR. High levels of paraxanthine were not independently associated with any of the studied outcomes and were confounded by smoking.

Elective induction of labour at full-term gestations and childhood school outcomes

AIM

To explore the association between induction of labour at full-term gestations in low-risk nulliparous women and childhood school outcomes.

METHODS

A retrospective whole-of-population cohort study linking perinatal data to educational test scores at grades 3, 5 and 7 in Victoria, Australia. Low-risk nulliparous women with singleton pregnancies induced at 39 and 40 weeks without a medical indication were compared to those expectantly managed from that week of gestation. Multivariable logistic regressions were used as well as generalised estimating equations on longitudinal data.

RESULTS

At 39 weeks, there were 3687 and 103 164 infants in the induction and expectant arms, respectively. At 40 weeks' gestation, there were 7914 and 70 280 infants, respectively. Infants born to nulliparous women induced at 39 weeks' gestation had significantly poorer educational outcomes at grade 3 (adjusted odds ratio (aOR) = 1.39, 95% confidence interval (CI): 1.13-1.70) but not grades 5 (aOR = 1.05, 95% CI: 0.84-1.33) and 7 (aOR = 1.07, 95% CI: 0.81-1.40) compared to those expectantly managed. Infants born to nulliparous women induced at 40 weeks had comparable educational outcomes at grade 3 (aOR = 1.06, 95% CI: 0.90-1.25) but poorer educational outcomes at grades 5 (aOR = 1.23, 95% CI: 1.05-1.43) and 7 (aOR = 1.23, 95% CI: 1.03-1.47) compared to those expectantly managed.

CONCLUSIONS

There were inconsistent associations between elective induction of labour at full-term gestations in low-risk nulliparous women and impaired childhood school outcomes.

The association between intrapartum interventions and immediate and ongoing breastfeeding outcomes: an Australian retrospective population-based cohort study

Background

The use of intrapartum interventions is becoming increasingly common globally. Interventions during birth, including caesarean section (CS), epidural analgesia and synthetic oxytocin infusion, can be important in optimizing obstetric care, but have the potential to impact breastfeeding. This study aimed to identify whether women who have certain intrapartum interventions have greater odds of unfavourable breastfeeding outcomes, both the immediate post-partum period and in the months after birth.

Methods

This was a population-based cohort study of singleton livebirths at ≥37 weeks’ gestation between 2010 and 2018 in Victoria, Australia using routinely-collected state-wide data from the Victorian Perinatal Data Collection (VPDC) and the Child Development Information System (CDIS). The interventions included were pre-labour CS, in-labour CS, epidural analgesia, and synthetic oxytocin infusion (augmentation and/or induction of labour). Outcomes were formula supplementation in hospital, method of last feed before hospital discharge and breastfeeding status at 3-months and 6-months. Descriptive statistics and multivariable logistic regression models adjusting for potential confounders were employed.

Results

In total, 599,191 women initiated breastfeeding. In-labour CS (aOR 1.96, 95%CI 1.93,1.99), pre-labour CS (aOR 1.75, 95%CI 1.72,1.77), epidural analgesia (aOR 1.45, 95%CI 1.43,1.47) and synthetic oxytocin infusion (aOR 1.24, 95%CI 1.22,1.26) increased the odds of formula supplementation in hospital. Long-term breastfeeding data was available for 105,599 infants. In-labour CS (aOR 0.79, 95%CI 0.76,0.83), pre-labour CS (aOR 0.73, 95%CI 0.71,0.76), epidural analgesia (aOR 0.77, 95%CI 0.75,0.80) and synthetic oxytocin infusion (aOR 0.89, 95%CI 0.86–0.92) decreased the odds of exclusive breastfeeding at 3-months post-partum, which was similar at 6-months. There was a dose-response effect between number of interventions received and odds of each unfavourable breastfeeding outcome.

Conclusion

Common intrapartum interventions are associated with less favourable breastfeeding outcomes, both in hospital and in the months after birth. This confirms the importance of only undertaking interventions when necessary. When interventions are used intrapartum, an assessment and identification of women at increased risk of early discontinuation of breastfeeding has to be performed. Targeted breastfeeding support for women who have intrapartum interventions, when they wish to breastfeed, is important.

The 5-minute Apgar score and childhood school outcomes

AIM

To examine the association between Apgar score at 5 min and childhood developmental and educational outcome.

METHODS

A population-based data linkage study of births ≥37 weeks' gestation linked to developmental outcomes at preparatory school and educational outcomes at school grades 3, 5 and 7 in Victoria, Australia. Multivariable logistic regressions and generalised estimating equations were used.

RESULTS

There were 167,126 singleton infants with developmental results and 392,933 singleton infants with at least one educational result. There was an inverse relationship between Apgar score at 5 min and poor developmental and educational outcomes, with the worst outcomes among Apgar scores of 0-3. Apgar scores of 7, 8 and 9 were all associated with poorer developmental outcomes (aOR = 1.31, 95% CI: 1.12-1.54; aOR = 1.17, 95% CI: 1.05-1.29; aOR = 1.08, 95% CI: 1.02-1.13 respectively), while Apgar scores of 7 and 8 were associated with poorer educational outcomes at grades 3, 5, and 7. With progression through grades 3, 5, and 7, the extent of the difference in educational outcomes diminished (e.g. for Apgar scores of 0-3: aOR = 3.33, 95% CI: 1.85-6.00 in grade 3 and aOR = 1.49, 95% CI: 0.75-2.96 in grade 7).

CONCLUSION

Apgar scores below 10 at 5 min are associated with poorer developmental and educational outcomes in school.

Routine first trimester combined screening for preterm preeclampsia in Australia: A multicenter clinical implementation cohort study

OBJECTIVE

To assess pregnancy outcomes following first trimester combined screening for preterm preeclampsia in Australia.

METHODS

We compared pregnancy outcomes of women with singleton pregnancies who underwent first trimester combined preeclampsia screening with the Fetal Medicine Foundation algorithm between 2014 and 2017 in Melbourne and Sydney, Australia, with those from women who received standard care. The primary outcomes were preterm preeclampsia and screening performance. Effect estimates were presented as risk ratios with 95% confidence intervals.

RESULTS

A total of 29 618 women underwent combined screening and 301 566 women received standard care. Women who had combined screening were less likely to have preeclampsia, preterm birth, small neonates, and low Apgar scores than the general population. Women with high-risk results (≥1 in 100) were more likely to develop preterm preeclampsia (2.1% vs. 0.7%, risk ratio [RR] 3.04, 95% CI 2.46-3.77), while low-risk women (risk <1 in 100) had lower rates of preterm preeclampsia (0.2% vs. 0.7%, RR 0.26, 95% CI 0.19-0.35) and other pregnancy complications. Screening detected 65.2% (95% CI 56.4-73.2%) of all preterm preeclampsia cases, with improved performance after adjustment for treatment effect.

CONCLUSIONS

First trimester screening for preeclampsia in clinical practice identified a population at high risk of adverse pregnancy outcomes and low-risk women who may be suitable for less intensive antenatal care.

Does detection of fetal growth restriction improve neonatal outcomes?

AIM

Timely delivery of fetal growth restriction (FGR) is a balance between avoiding stillbirth and minimising prematurity. We sought to assess the neonatal outcomes for babies suspected of FGR, both true and false positives.

METHODS

This population cohort study examined all singleton births in Victoria, Australia from 2000 to 2017 (n = 1 231 415). Neonatal morbidities associated with neonatal intensive care unit (NICU) admission were assessed for babies born ≥32 weeks' with severe FGR (<3rd centile) and babies with birthweight ≥10th centile who were iatrogenically delivered for suspected FGR.

RESULTS

Babies with severe FGR iatrogenically delivered for suspected FGR were more likely to require NICU admission than babies with severe FGR who were not detected (3.0% vs. 1.1%, P < 0.001). After adjusting for potential confounders, the odds of NICU admission were increased (adjusted odds ratio (aOR) = 3.00, 95% confidence interval = 2.45-3.67; P < 0.001). Rates of NICU admission were also higher in ≥10th centile babies iatrogenically delivered for suspected FGR than for ≥10th centile babies who entered labour spontaneously (1.8% vs. 0.5%, P < 0.001). After adjustments, the odds of NICU admission were increased (aOR = 3.91, 95% confidence interval = 3.40-4.49; P < 0.001). NICU admissions were associated with morbidities related to iatrogenic prematurity.

CONCLUSIONS

Detection and planned delivery of FGR reduces stillbirth but may be associated with increased neonatal morbidity related to iatrogenic prematurity.

Preventing harm: A balance measure for improving the detection of fetal growth restriction

BACKGROUND

Increasing the detection of fetal growth restriction (FGR), while reducing stillbirth, also leads to unnecessary early intervention, and associated morbidity, for normally grown babies who are incorrectly suspected of FGR.

AIMS

We sought to design a balance measure that addresses the specificity of FGR detection.

METHODS

A retrospective cohort study on all singleton births ≥32 weeks gestation in 2016 and 2017 in Victoria. We compared two balance measures for the detection of FGR, defined as the proportion of all babies iatrogenically delivered before 39 weeks gestation for suspected FGR that had a birthweight ≥10th centile (balance measure 1) or ≥25th centile (balance measure 2). Hospital level performance on each balance measure was derived and compared to an existing performance measure for severe FGR detection in Victoria.

RESULTS

Of the 38 hospitals analysed, 12 (32%) had a favourable performance on an existing indicator of FGR detection, seven (18%) hospitals had a favourable performance on balance measure 1, and 15 (39%) had a favourable performance on balance measure 2. There was a moderate correlation between hospital performance on the existing indicator and on balance measure 1 (r = 0.447, P = 0.005) but not balance measure 2 (r = -0.063, P = 0.71). There was no difference in perinatal mortality between high performing hospitals and low performing hospitals.

CONCLUSION

Introducing a balance measure into routine reporting may bring greater awareness to the unintended harm associated with increased detection of FGR.

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.