Theoretical and empirical justification for current rates of iatrogenic delivery at late preterm gestation

Obstetric Intervention and Perinatal Outcomes During the Coronavirus Disease 2019 (COVID-19) Pandemic

OBJECTIVE

To quantify pandemic-related changes in obstetric intervention and perinatal outcomes in the United States.

METHODS

We carried out a retrospective study of all live births and fetal deaths in the United States, 2015-2021, with data obtained from the natality, fetal death, and linked live birth-infant death files of the National Center for Health Statistics. Analyses were carried out among all singletons; singletons of patients with prepregnancy diabetes, prepregnancy hypertension, and hypertensive disorders of pregnancy; and twins. Outcomes of interest included preterm birth, preterm labor induction or preterm cesarean delivery, macrosomia, postterm birth, and perinatal death. Interrupted time series analyses were used to estimate changes in the prepandemic period (January 2015-February 2020), at pandemic onset (March 2020), and in the pandemic period (March 2020-December 2021).

RESULTS

The study population included 26,604,392 live births and 155,214 stillbirths. The prepandemic period was characterized by temporal increases in preterm birth and preterm labor induction or cesarean delivery rates and temporal reductions in macrosomia, postterm birth, and perinatal mortality. Pandemic onset was associated with absolute decreases in preterm birth (decrease of 0.322/100 live births, 95% CI 0.506-0.139) and preterm labor induction or cesarean delivery (decrease of 0.190/100 live births, 95% CI 0.334-0.047) and absolute increases in macrosomia (increase of 0.046/100 live births), postterm birth (increase of 0.015/100 live births), and perinatal death (increase of 0.501/1,000 total births, 95% CI 0.220-0.783). These changes were larger in subpopulations at high risk (eg, among singletons of patients with prepregnancy diabetes). Among singletons of patients with prepregnancy diabetes, pandemic onset was associated with a decrease in preterm birth (decrease of 1.634/100 live births) and preterm labor induction or cesarean delivery (decrease of 1.521/100 live births) and increases in macrosomia (increase of 0.328/100 live births) and perinatal death (increase of 9.840/1,000 total births, 95% CI 3.933-15.75). Most changes were reversed in the months after pandemic onset.

CONCLUSION

The onset of the coronavirus disease 2019 (COVID-19) pandemic was associated with a transient decrease in obstetric intervention (especially preterm labor induction or cesarean delivery) and a transient increase in perinatal mortality.

US term stillbirth rates and the 39-week rule: a cause for concern?

BACKGROUND

More than a decade ago an obstetric directive called "the 39-week rule" sought to limit "elective" delivery, via labor induction or cesarean delivery, before 39 weeks 0 days of gestation. In 2010 the 39-week rule became a formal quality measure in the United States. The progressive adherence to the 39-week rule throughout the United States has caused a well-documented, progressive reduction in the proportion of term deliveries occurring during the early-term period. Because of the known association between increasing gestational age during the term period and increasing cumulative risk of stillbirth, however, there have been published concerns that the 39-week rule-by increasing the gestational age of delivery for a substantial number of pregnancies-might increase the rate of term stillbirth within the United States. Although adherence to the 39-week rule is assumed to be beneficial, its actual impact on the US rate of term stillbirth in the years since 2010 is unknown.

OBJECTIVE

To determine whether the adoption of the 39-week rule was associated with an increased rate of term stillbirth in the United States.

STUDY DESIGN

Sequential ecological study, based on state data, of US term deliveries that occurred during a 7-year period bounded by 2007 and 2013. The patterns of the timing of both term childbirth and term stillbirth were determined for each state and for the United States as a whole.

RESULTS

A total of 46 usable datasets were obtained (45 states and the District of Columbia). During the 7-year period, there was a continuous reduction in all geographic entities in the proportion of term deliveries that occurred before 39 weeks of gestation. The overall rate of term stillbirth, when we compared 2007-2009 with 2011-2013, increased significantly (1.103/1000 vs 1.177/1000, RR 1.067, 95% confidence interval 1.038-1.096). Furthermore, during the 7-year period, the increase in the rate of US term stillbirth appeared to be continuous (estimated slope: 0.0186/1000/year, 95% confidence interval 0.002-0.035). Assuming 3.5 million term US births per year, and given 6 yearly "intervals" with this rate increase, it is possible that more than 335 additional term stillbirths occurred in the United States in 2013 as compared with 2007. In addition, during the 7-year period, there was a progressive shift in the timing of delivery from the 40th week to the 39th week. Absent this confounding factor, the magnitude of association between the adoption of the 39-week rule and the increase in rate of term stillbirth might have been greater.

CONCLUSIONS

Between 2007 and 2013 in the United States, the adoption of the 39-week rule caused a progressive reduction in the proportion of term births occurring before the 39th week of gestation. During the same interval the United States experienced a significant increase in its rate of term stillbirth. This study raises the possibility that the 39-week rule may be causing unintended harm. Additional studies of the actual impact of the adoption of the 39-week rule on major childbirth outcomes are urgently needed. Pressures to enforce the 39-week rule should be reconsidered pending the findings of such studies.

What contributes to disparities in the preterm birth rate in European countries?

PURPOSE OF REVIEW

In countries with comparable levels of development and healthcare systems, preterm birth rates vary markedly--a range from 5 to 10% among live births in Europe. This review seeks to identify the most likely sources of heterogeneity in preterm birth rates, which could explain differences between European countries.

RECENT FINDINGS

Multiple risk factors impact on preterm birth. Recent studies reported on measurement issues, population characteristics, reproductive health policies as well as medical practices, including those related to subfertility treatments and indicated deliveries, which affect preterm birth rates and trends in high-income countries. We showed wide variation in population characteristics, including multiple pregnancies, maternal age, BMI, smoking, and percentage of migrants in European countries.

SUMMARY

Many potentially modifiable population factors (BMI, smoking, and environmental exposures) as well as health system factors (practices related to indicated preterm deliveries) play a role in determining preterm birth risk. More knowledge about how these factors contribute to low and stable preterm birth rates in some countries is needed for shaping future policy. It is also important to clarify the potential contribution of artifactual differences owing to measurement.

Neonatal outcomes of late preterm and early term birth

OBJECTIVE

To compare neonatal deaths and complications in infants born at 34-36 weeks and six days (late preterm: LPT) with those born at term (37-41 weeks and six days); to compare deaths of early term (37-38 weeks) versus late term (39-41 weeks and six days) infants; to search for any temporal trend in LPT rate.

STUDY DESIGN

A retrospective cohort study of live births was conducted in the Campinas State University, Brazil, from January 2004 to December 2010. Multiple pregnancies, malformations and congenital diseases were excluded. Control for confounders was performed. The level of significance was set at p<0.05.

RESULTS

After exclusions, there were 17,988 births (1653 late preterm and 16,345 term infants). A higher mortality in LPT versus term was observed, with an adjusted odds ratio (OR) of 5.29 (p<0.0001). Most complications were significantly associated with LPT births. There was a significant increase in LPT rate throughout the study period, but no significant trend in the rate of medically indicated deliveries. A higher mortality was observed in early term versus late term infants, with adjusted OR: 2.43 (p=0.038).

CONCLUSION

LPT and early term infants have a significantly higher risk of death.

The association between obstetrical interventions and late preterm birth

OBJECTIVE

There is concern that obstetric interventions (prelabor cesarean section and induced delivery) are drivers of late preterm (LP) birth. Our objective was to evaluate the independent association between obstetric interventions and LP birth and explore associated independent maternal and fetal risk factors for LP birth.

STUDY DESIGN

In this population-based cross-sectional study, the BORN Information System was used to identify all infants born between 34 and 40 completed weeks of gestation between 2005 and 2012 in Ontario, Canada. The association between obstetric interventions (preterm cesarean section and induced delivery) and LP birth (34 to 36 completed weeks' gestation vs 37 to 40 completed weeks' gestation) was assessed using generalized estimating equation regression.

RESULTS

Of 917,013 births between 34 and 40 weeks, 49,157 were LP (5.4%). In the adjusted analysis, "any obstetric intervention" (risk ratio [RR], 0.65; 95% confidence interval [CI], 0.57-0.74), induction (RR, 0.71; 95% CI, 0.61-0.82) and prelabor cesarean section (RR, 0.66; 95% CI, 0.59-0.74) were all associated with a lower likelihood of LP vs term birth. Several independent potentially modifiable risk factors for LP birth were identified including previous cesarean section (RR, 1.28; 95% CI, 1.16-1.40), smoking during pregnancy (RR, 1.28; 95% CI, 1.21-1.36) and high material (RR, 1.1; 95% CI, 1.03-1.18) and social (RR, 1.09; 95% CI, 1.02-1.16) deprivation indices.

CONCLUSION

After accounting for differences in maternal and fetal risk, LP births had a 35% lower likelihood of obstetric interventions than term births. Obstetric care providers may be preferentially avoiding induction and prelabor cesarean section between 34 and 37 weeks' gestation.

Temporal trends in stillbirth in the United States, 1992-2004: a population-based cohort study

OBJECTIVE

To examine temporal trends in stillbirth and its risk factors in the United States (US), and to assess the contribution of labour induction and caesarean delivery to the stillbirth rate.

DESIGN

Population-based cohort study based on linked birth-infant death and fetal death data files from the US National Vital Statistics System.

SETTING

Complete data were available for 44 states and the District of Columbia.

POPULATION OR SAMPLE

Singleton births from 1992 to 2004.

METHODS

We assessed changes in stillbirth rates from 1992-1994 to 2002-2004 before and after adjustment for changes in maternal characteristics including maternal age, education, smoking, and medical risk factors, using Cox regression models. We also carried out an ecological study, using states as the units of analysis, to assess the impact on the stillbirth rate of increasing induction and caesarean delivery. Race-specific subgroup analyses were performed and included non-Hispanic Whites and non-Hispanic Blacks.

MAIN OUTCOME MEASURE

Stillbirth rate.

RESULTS

The stillbirth rate among non-Hispanic White singleton births decreased 11.5% from 1992-1994 (5.2 per 1000) to 2002-2004 (4.6 per 1000). After adjustment for maternal risk factors, the hazard ratio (HR) for 2002-2004 was 1.01 (0.99, 1.03) for gestational age (GA) ≤39 weeks, but 0.92 (0.86, 0.99) at 40 or more weeks. The ecologic analysis revealed a nonsignificant negative correlation of -0.17 (-0.44, 0.13) between state-level changes in stillbirth at GA ≥40 weeks and labour induction. A nonsignificant positive correlation of 0.23 (-0.07, 0.49) was observed between changes in stillbirth at all GAs and caesarean delivery and did not differ at GA ≤39 versus ≥40 weeks. Results were similar among non-Hispanic Blacks.

CONCLUSIONS

Changes in maternal risk factors explained the reduction in stillbirth at GA ≤39 weeks but not at ≥40 weeks. The rise in labour induction and caesarean delivery rates did not explain the reduction in stillbirth ≥40 weeks of gestation.

Late prematurity: a systematic review

OBJECTIVE

this study aimed to review the literature regarding late preterm births (34 weeks to 36 weeks and 6 days of gestation) in its several aspects.

SOURCES

the MEDLINE, LILACS, and Cochrane Library databases were searched, and the references of the articles retrieved were also used, with no limit of time.

DATA SYNTHESIS

numerous studies showed a recent increase in late preterm births. In all series, late preterm comprised the majority of preterm births. Studies including millions of births showed a strong association between late preterm birth and neonatal mortality. A higher mortality in childhood and among young adults was also observed. Many studies found an association with several neonatal complications, and also with long-term disorders and sequelae: breastfeeding problems, cerebral palsy, asthma in childhood, poor school performance, schizophrenia, and young adult diabetes. Some authors propose strategies to reduce late preterm birth, or to improve neonatal outcome: use of antenatal corticosteroids, changes in some of the guidelines for early delivery in high-risk pregnancies, and changes in neonatal care for this group.

CONCLUSIONS

numerous studies show greater mortality and morbidity in late preterm infants compared with term infants, in addition to long-term disorders. More recent studies evaluated strategies to improve the outcomes of these neonates. Further studies on these strategies are needed.