Inadequate Timing Limits the Benefit of Antenatal Corticosteroids on Neonatal Outcome: Retrospective Analysis of a High-Risk Cohort of Preterm Infants in a Tertiary Center in Germany

The influence of antenatal betamethasone timing on neonatal outcome in late preterm infants: a single-center cohort study

PURPOSE

Many pregnancies continue after antenatal corticosteroid exposure. Since long-term effects on late preterm neonatal outcome remain controversial, it remains unknown whether pregnant women who are at risk for preterm birth during the late preterm period and had prior antenatal corticosteroid exposure would benefit from an additional course of antenatal corticosteroids. We evaluated the need for future trials on this topic by comparing short term effects from antenatal betamethasone to long-term effects. We also examined the value of a risk-adapted approach.

METHODS

We observed neonatal outcomes in late preterm infants (34/0-36/0 weeks of gestation) who were exposed to antenatal betamethasone either up to 10 days prior birth (n = 8) or earlier in pregnancy (n = 89). We examined a real world population from the University Hospital Magdeburg (Germany) between 01 January 2012 and 31 December 2018, and a simulated high-risk population that was derived from the original data.

RESULTS

The indicators for relevant adverse outcomes did not differ in the unselected population. In the simulated high-risk population, recent antenatal corticosteroid administration significantly reduced the incidence of relevant cardiorespiratory morbidities (OR = 0.00, p = 0.008), and reduced the number needed to treat from 3.7 to 1.5.

CONCLUSION

The superiority of recent antenatal corticosteroid administration in the late preterm period over earlier exposure strongly depended on the prevalence of respiratory disease. Before considering clinical trials on additional antenatal corticosteroid courses in the late preterm period, antenatal assessment tools to predict respiratory morbidity need to be developed.

Administration of Antenatal Corticosteroids: Optimal Timing

The effectiveness of antenatal corticosteroids (ACS) in significantly reducing respiratory distress syndrome (RDS) depends crucially on the timing. It is successful if delivery takes place between 24 hours and seven days following administration; after this period, the side effects seem to predominate. In addition, an increased rate of mental impairment and behavioral disorders are observed in children born full-term after ACS administration. The optimal timing of ACS administration depends crucially on the given indication; to date, it has been achieved in only 25-40% of cases. ACS administration is always indicated in PPROM, in severe early pre-eclampsia, in fetal IUGR with zero or reverse flow in the umbilical artery, in placenta previa with bleeding, and in patients experiencing premature labor with a cervical length < 15 mm. The risk of women with asymptomatic cervical insufficiency giving birth within seven days is very low. In this case, ACS should not be administered even if the patient's cervical length is less than 15 mm, provided that the cervix is closed and there are no other risk factors for a premature birth. The development of further diagnostic methods with improved power to predict premature birth is urgently needed in order to optimize the timing of ACS administration in this patient population. Caution when administering ACS is also indicated in women experiencing premature labor who have a cervical length ≥ 15 mm. Further studies using amniocentesis are needed in order to identify the patient population with microbial invasion of the amniotic cavity/intra-amniotic infection (MIAC/IAI), and to define threshold values at which delivery is indicated. ACS administration is not performed as an emergency measure, usually not even before transfer to a perinatal center. Therefore, whenever possible, the indication for ACS administration should be determined by a clinician who is highly experienced in perinatology.

Effect of antenatal corticosteroid administration-to-birth interval on maternal and newborn outcomes: a systematic review

Background

Antenatal corticosteroids (ACS) are highly effective at improving outcomes for preterm newborns. Evidence suggests the benefits of ACS may vary with the time interval between administration-to-birth. However, the optimal ACS administration-to-birth interval is not yet known. In this systematic review, we synthesised available evidence on the relationship between ACS administration-to-birth interval and maternal and newborn outcomes.

Methods

This review was registered with PROSPERO (CRD42021253379). We searched Medline, Embase, CINAHL, Cochrane Library, Global Index Medicus on 11 Nov 2022 with no date or language restrictions. Randomised and non-randomised studies of pregnant women receiving ACS for preterm birth where maternal and newborn outcomes were reported for different administration-to-birth intervals were eligible. Eligibility screening, data extraction and risk of bias assessment were performed by two authors independently. Fetal and neonatal outcomes included perinatal and neonatal mortality, preterm birth-related morbidity outcomes and mean birthweight. Maternal outcomes included chorioamnionitis, maternal mortality, endometritis, and maternal intensive care unit admission.

Findings

Ten trials (4592 women; 5018 neonates), 45 cohort studies (at least 22,992 women; 30,974 neonates) and two case-control studies (355 women; 360 neonates) met the eligibility criteria. Across studies, 37 different time interval combinations were identified. There was considerable heterogeneity in included administration-to-birth intervals and populations. The odds of neonatal mortality, respiratory distress syndrome and intraventricular haemorrhage were associated with the ACS administration-to-birth interval. However, the interval associated with the greatest improvements in newborn outcomes was not consistent across studies. No reliable data were available for maternal outcomes, though odds of chorioamnionitis might be associated with longer intervals.

Intepretation

An optimal ACS administration-to-birth interval likely exists, however variations in study design limit identification of this interval from available evidence. Future research should consider advanced analysis techniques such as individual patient data meta-analysis to identify which ACS administration-to-birth intervals are most beneficial, and how these benefits can be optimised for women and newborns.

Funding

This study was conducted with funding support from the UNDP-UNFPA-UNICEF-WHO-World Bank Special Programme of Research, Development and Research Training in Human Reproduction (HRP), Department of Sexual and Reproductive Health and Research (SRH), a co-sponsored programme executed by the World Health Organization.