Propensity score analysis of low-dose aspirin and bleeding complications in pregnancy

OBJECTIVE

Low-dose aspirin (LDA) has been shown to reduce the risk of preterm pre-eclampsia and it has been suggested that it should be recommended for all pregnancies. However, some studies have reported an association between LDA and an increased risk of bleeding complications in pregnancy. Our aim was to evaluate the risk of placental abruption and postpartum hemorrhage (PPH) in patients for whom their healthcare provider had recommended prophylactic aspirin.

METHODS

This multicenter cohort study included 72 598 singleton births at 19 hospitals in the USA, between January 2019 and December 2021. Pregnancies complicated by placenta previa/accreta, birth occurring at less than 24 weeks' gestation, multiple pregnancy or those with data missing for aspirin recommendation were excluded. Propensity scores were calculated using 20 features spanning sociodemographic factors, medical history, year and hospital providing care. The association between LDA recommendation and placental abruption or PPH was estimated by inverse-probability treatment weighting using the propensity scores.

RESULTS

We included 71 627 pregnancies in the final analysis. Aspirin was recommended to 6677 (9.3%) and was more likely to be recommended for pregnant individuals who were 35 years or older (P < 0.001), had a body mass index of 30 kg/m2 or higher (P < 0.001), had prepregnancy hypertension (P < 0.001) and who had a Cesarean delivery (P < 0.001). Overall, 1.7% of the study cohort (1205 pregnancies) developed preterm pre-eclampsia: 1.3% in the no-aspirin and 5.8% in the aspirin group. After inverse-probability weighting with propensity scores, aspirin was associated with increased risk of placental abruption (adjusted odds ratio (aOR), 1.44 (95% CI, 1.04-2.00)) and PPH (aOR, 1.21 (95% CI, 1.05-1.39)). The aOR translated to a number needed to harm with LDA of 79 (95% CI, 43-330) for PPH and 287 (95% CI, 127-3151) for placental abruption.

CONCLUSIONS

LDA recommendation in pregnancy was associated with increased risk for placental abruption and for PPH. Our results support the need for more research into aspirin use and bleeding complications in pregnancy before recommending it beyond the highest-risk pregnancies. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Effects of the ARRIVE (A Randomized Trial of Induction Versus Expectant Management) Trial on Elective Induction and Obstetric Outcomes in Term Nulliparous Patients

OBJECTIVE

To evaluate the effect of publication of the ARRIVE (A Randomized Trial of Induction Versus Expectant Management) trial on perinatal outcomes in singleton, term, nulliparous patients.

METHODS

An interrupted time series analysis was performed using clinical data for nulliparous singleton births at 39 weeks of gestation or later at 13 hospitals in the Northwest region of the United States (January 2016-December 2020). A modified Poisson regression was used to model time trends and changes after the ARRIVE trial (August 9, 2018). Outcomes of interest were elective induction, unplanned cesarean births, hypertensive disorders of pregnancy, a composite of perinatal adverse outcomes, and neonatal intensive care unit admissions.

RESULTS

The analysis included 28,256 births (15,208 pre-ARRIVE and 13,048 post-ARRIVE). The rate of elective labor induction was 3.6% during the pre-ARRIVE period (January 2016-July 2018) and 10.8% post-ARRIVE (August 2018-December 2020). In the interrupted time series analysis, elective induction increased by 42% (relative risk [RR] 1.42; 95% CI 1.18-1.71) immediately after the ARRIVE trial publication. Thereafter, the trend was unchanged compared with the pre-ARRIVE period. There was no statistically significant change in cesarean birth (RR 0.96; 95% CI 0.89-1.04) or hypertensive disorders of pregnancy (RR 0.91; 95% CI 0.79-1.06) immediately after the trial, and no change in trend. After the ARRIVE trial, there was no immediate change in adverse perinatal outcomes, but a statistically significant increase in trend of adverse perinatal events (1.03; 95% CI 1.01-1.05) when compared with a declining trend observed in the pre-ARRIVE period.

CONCLUSION

Publication of the ARRIVE trial was associated with an increase in elective induction, and no change in cesarean birth or hypertensive disorders of pregnancy in singleton nulliparous patients giving birth at 39 weeks or later. There was a flattening of the pre-ARRIVE decreasing trend in perinatal adverse events.

Exclusive Breastfeeding in the Northwest: Disparities Related to Race/Ethnicity and Substance Use

BACKGROUND AND OBJECTIVES

Mothers who are Black, Indigenous, and people of color (BIPOC) are disproportionately impacted by substance use in pregnancy and less likely to breastfeed. Our objectives were to assess relationships between substance use in pregnancy and exclusive breastfeeding at discharge (EBF) and race/ethnicity and EBF, and determine the extent to which substance use influences the relationship between race/ethnicity and EBF.

METHODS

This is a retrospective cohort study of term mother-infant dyads using 2016 to 2019 data from a Northwest quality improvement collaborative, Obstetrical Care Outcomes Assessment Program. Stepwise and stratified multivariable logistic regression analyses were conducted to determine associations between independent variables consisting of characteristics, including maternal race/ethnicity and substance use, and the dependent variable, EBF.

RESULTS

Our sample consisted of 84,742 dyads, 69.5% of whom had EBF. The adjusted odds of EBF for non-Hispanic Black and Hispanic mothers were half, and for American Indian/Alaska Native mothers two-thirds, that of White mothers (aOR [95% CI]: 0.52 [0.48, 0.57], 0.51 [0.48, 0.54], 0.64 [0.55, 0.76], respectively). Substance use did not mediate the association between race/ethnicity and EBF, but it modified the association. Among those reporting nicotine or marijuana use, Hispanic mothers were half as likely as White mothers were to exclusively breastfeed. Other factors associated with a lower likelihood of EBF included public or no insurance, rural setting, C-section, NICU admission, and LBW.

CONCLUSIONS

Disparities in EBF related to race/ethnicity and substance use were pronounced in this study, particularly among Hispanic mothers with nicotine or marijuana use.

Customized GROW vs INTERGROWTH-21st birthweight standards to identify small for gestational age associated perinatal outcomes at term

BACKGROUND

Fetal growth restriction is associated with stillbirth and other adverse pregnancy outcomes, and use of the correct weight standard is an essential proxy indicator of growth status and perinatal risk.

OBJECTIVE

We sought to assess the performance of two international birthweight standards for their ability to identify perinatal morbidity and mortality indicators associated with small for gestational age (SGA) infants at term.

STUDY DESIGN

This retrospective cohort study used data from a multi-center perinatal quality initiative including a multi-ethnic dataset of 125,826 births from 2012-2017. Of the singleton term births, 92,622 had complete outcome data including stillbirth, neonatal death, 5-minute Apgar <7, neonatal glucose instability and need for newborn transfer to a higher level of care or NICU admission. The customized (GROW) and INTERGROWTH-21^st (IG21) birthweight standards were applied to determine SGA (<10^th centile) according to their respective methods and formulae. Associations with adverse outcomes were expressed as relative risk (RR) with 95% confidence interval (CI) and population attributable fraction (PAF).

RESULTS

GROW classified 9,578 (10.3%) and IG21 classified 4,079 (4.4%) pregnancies as SGA, respectively. For all of the outcomes assessed, GROW identified more SGA infants with adverse outcomes than IG21, including more stillbirths, perinatal deaths, low Apgar scores, glucose instability, newborn seizure and transfers to a higher level of care. Thirteen of the 27 stillbirths (48%) that were SGA by either method were identified as SGA by GROW but not by IG21. Similarly, additional cases of all other adverse outcome indicators were identified by GROW as SGA, while only in one category (glucose instability) did IG21 identify 9 of 295 cases (3.1%) which were not identified as SGA by GROW.

CONCLUSION

Customized assessment using GROW results in increased identification of small for gestational age term babies that are at significantly increased risk of an array of adverse pregnancy outcomes.

A Simple Approach to Adjust for Case-Mix When Comparing Institutional Cesarean Birth Rates

OBJECTIVE

This study aimed to develop a validated model to predict intrapartum cesarean in nulliparous women and to use it to adjust for case-mix when comparing institutional laboring cesarean birth (CB) rates.

STUDY DESIGN

This multicenter retrospective study used chart-abstracted data on nulliparous, singleton, term births over a 7-year period. Prelabor cesareans were excluded. Logistic regression was used to predict the probability of CB for individual pregnancies. Thirty-five potential predictive variables were evaluated including maternal demographics, prepregnancy health, pregnancy characteristics, and newborn weight and gender. Models were trained on 21,017 births during 2011 to 2015 (training cohort), and accuracy assessed by prediction on 15,045 births during 2016 to 2017 (test cohort).

RESULTS

Six variables delivered predictive success equivalent to the full set of 35 variables: maternal weight, height, and age, gestation at birth, medically-indicated induction, and birth weight. Internal validation within the training cohort gave a receiver operator curve with area under the curve (ROC-AUC) of 0.722. External validation using the test cohort gave ROC-AUC of 0.722 (0.713-0.731 confidence interval). When comparing observed and predicted CB rates at 16 institutions in the test cohort, five had significantly lower than predicted rates and three had significantly higher than predicted rates.

CONCLUSION

Six routine clinical variables used to adjust for case-mix can identify outliers when comparing institutional CB rates.