Late-preterm births: challenges and opportunities

What happens to 35 week infants that receive delivery room continuous positive airway pressure?

OBJECTIVE

Delivery room (DR) continuous positive airway pressure (CPAP) is increasing. Our study examined the risk for neonatal morbidities after DR CPAP in 35 week neonates.

STUDY DESIGN

A retrospective study of 259 infants born at 35 weeks gestational age between January 1, 2017-December 31, 2018 at a single center.

RESULTS

DR resuscitation was administered in 30.5%, with 19.7% receiving CPAP alone. Eighty percent who received DR CPAP were admitted to the NICU. DR CPAP was associated with the highest NICU admission risk, 9.3 times the risk of those without DR positive pressure, and with respiratory conditions (RDS: OR 4.22 {CI 1.46-11.51}, TTN: OR 3.30 {CI 1.36-7.64}). For the DR CPAP group, non-invasive positive pressure was administered post resuscitation in 90%.

CONCLUSIONS

In our institution, 35 week infants frequently received DR CPAP. Of these infants, a majority were admitted to the NICU for respiratory disorders.

Acute Kidney Injury is Associated with Poor Lung Outcomes in Infants Born ≥32 Weeks of Gestational Age

OBJECTIVE

This study aimed to evaluate the association between acute kidney injury (AKI) and lung outcomes in infants born ≥32 weeks of gestational age (GA).

STUDY DESIGN

Secondary analysis of infants ≥32 weeks of GA in the assessment of worldwide acute kidney injury epidemiology in neonates (AWAKEN) retrospective cohort (n = 1,348). We used logistic regression to assess association between AKI and a composite outcome of chronic lung disease (CLD) or death at 28 days of age and linear regression to evaluate association between AKI and duration of respiratory support.

RESULTS

CLD occurred in 82/1,348 (6.1%) infants, while death occurred in 22/1,348 (1.6%); the composite of CLD/death occurred in 104/1,348 (7.7%). Infants with AKI had an almost five-fold increased odds of CLD/death, which remained after controlling for GA, maternal polyhydramnios, multiple gestations, 5-minute Apgar's score, intubation, and hypoxic-ischemic encephalopathy (adjusted odds ratio [OR] = 4.9, 95% confidence interval [CI]: 3.2-7.4; p < 0.0001). Infants with AKI required longer duration of respiratory support (count ratio = 1.59, 95% CI: 1.14-2.23, p = 0.003) and oxygen (count ratio = 1.43, 95% CI: 1.22-1.68, p < 0.0001) compared with those without AKI.

CONCLUSION

AKI is associated with CLD/death and longer duration of respiratory support in infants born at ≥32 weeks of GA. Further prospective studies are needed to elucidate the pathophysiologic relationship.

Towards reducing variations in infant mortality and morbidity: a population-based approach

Background

Our aims were (1) to improve understanding of regional variation in early-life mortality rates and the UK’s poor performance in international comparisons; and (2) to identify the extent to which late and moderately preterm (LMPT) birth contributes to early childhood mortality and morbidity.

Objective

To undertake a programme of linked population-based research studies to work towards reducing variations in infant mortality and morbidity rates.

Design

Two interlinked streams: (1) a detailed analysis of national and regional data sets and (2) establishment of cohorts of LMPT babies and term-born control babies.

Setting

Cohorts were drawn from the geographically defined areas of Leicestershire and Nottinghamshire, and analyses were carried out at the University of Leicester.

Data sources

For stream 1, national data were obtained from four sources: the Office for National Statistics, NHS Numbers for Babies, Centre for Maternal and Child Enquiries and East Midlands and South Yorkshire Congenital Anomalies Register. For stream 2, prospective data were collected for 1130 LMPT babies and 1255 term-born control babies.

Main outcome measures

Detailed analysis of stillbirth and early childhood mortality rates with a particular focus on factors leading to biased or unfair comparison; review of clinical, health economic and developmental outcomes over the first 2 years of life for LMPT and term-born babies.

Results

The deprivation gap in neonatal mortality has widened over time, despite government efforts to reduce it. Stillbirth rates are twice as high in the most deprived as in the least deprived decile. Approximately 70% of all infant deaths are the result of either preterm birth or a major congenital abnormality, and these are heavily influenced by mothers’ exposure to deprivation. Births at < 24 weeks’ gestation constitute only 1% of all births, but account for 20% of infant mortality. Classification of birth status for these babies varies widely across England. Risk of LMPT birth is greatest in the most deprived groups within society. Compared with term-born peers, LMPT babies are at an increased risk of neonatal morbidity, neonatal unit admission and poorer long-term health and developmental outcomes. Cognitive and socioemotional development problems confer the greatest long-term burden, with the risk being amplified by socioeconomic factors. During the first 24 months of life each child born LMPT generates approximately £3500 of additional health and societal costs.

Conclusions

Health professionals should be cautious in reviewing unadjusted early-life mortality rates, particularly when these relate to individual trusts. When more sophisticated analysis is not possible, babies of < 24 weeks’ gestation should be excluded. Neonatal services should review the care they offer to babies born LMPT to ensure that it is appropriate to their needs. The risk of adverse outcome is low in LMPT children. However, the risk appears higher for some types of antenatal problems and when the mother is from a deprived background.

Future work

Future work could include studies to improve our understanding of how deprivation increases the risk of mortality and morbidity in early life and investigation of longer-term outcomes and interventions in at-risk LMPT infants to improve future attainment.

Funding

The National Institute for Health Research Programme Grants for Applied Research programme.

Comparison of placental pathology in preterm, late-preterm, near-term, and term births

OBJECTIVE

The purpose of this study was to determine whether placental pathologic condition supports the recent suggestion of subcategorizing preterm and term births into smaller gestational age subgroups with different perinatal mortality and morbidity rates.

STUDY DESIGN

Twenty-seven clinical and 43 placental phenotypes were retrospectively compared in 4617 third-trimester births: 1332 preterm pregnancies (28-33 weeks' gestation), 1066 late preterm pregnancies (34-36 weeks' gestation), 940 near-term pregnancies (37-38 weeks' gestation), and 1279 term pregnancies (≥39 weeks' gestation).

RESULTS

Acute inflammatory pattern of placental injury was seen mostly at both gestational sides of the third trimester; the clinical conditions linked to in utero hypoxia (preeclampsia, diabetes mellitus, fetal growth restriction) and their placental associations (atherosis, membrane chorionic microcysts, chorangiosis, intervillous thrombi) were associated statistically significantly with mid third trimester. Acute fetal distress (abnormal fetal heart tracing and clinical and histologic meconium) were increasing with gestational age and were statistically significantly most common in full-term pregnancies.

CONCLUSION

Differences in placental pathologic condition among the 4 subgroups of third-trimester pregnancy not only challenge the use of an arbitrary cutoff point of 37 weeks' gestation that separates the preterm birth and term birth but also further support separation of late preterm births from preterm births and term births from near-term births. Based on placental pathologic condition, chronic uteroplacental malperfusion is the dominating etiopathogenetic factor in the mid third trimester (late preterm and near-term births), and acute fetal distress is the factor in full-term births. This obscures relative frequencies of perinatal death and management modalities in the third trimester.

Management of breastfeeding during and after the maternity hospitalization for late preterm infants

Among infants born moderately and late preterm or early term, the greatest challenge for breastfeeding management is the late preterm infant (LPI) who is cared for with the mother in the maternity setting. Breastfeeding failure among LPIs and their mothers is high. Evidence-based strategies are needed to protect infant hydration and growth, and the maternal milk supply, until complete feeding at breast can be established. This article reviews the evidence for lactation and breastfeeding risks in LPIs and their mothers, and describes strategies for managing these immaturity-related feeding problems. Application to moderately and early preterm infants is made throughout.

Neurological maturation of late preterm infants at 34 wk assessed by amplitude integrated electroencephalogram

BACKGROUND

This study tested if measures of central nervous system (CNS) immaturity reflected by amplitude integrated electroencephalogram (aEEG) and associated clinical morbidities are determinants of length of hospitalization among late preterm infants born at 34 wk.

METHODS

This was a prospective cohort study of infants with a gestational age of 34 wk 0-6 d who had a single aEEG recording acquired over 6 h in a neonatal intensive care unit within 72 h of birth (n = 80). Infants were followed for predefined morbidities (classified as CNS or non-CNS) and length of hospitalization (determined by the clinical care team). aEEG variables were correlated with length of hospitalization.

RESULTS

Eighty infants were enrolled and 75 aEEG recordings were analyzed. The average length of hospitalization was 10.4 ± 7.2 d (range 3-46 d). The total number of cycles recorded in the first 72 h following birth were inversely correlated with the length of hospitalization (r(2) = 0.44, P < 0.001). Kaplan-Meier curves indicated that morbidities consistent with neurological immaturity were associated with a longer length of hospitalization (P < 0.001).

CONCLUSION

Neurological maturation as indicated by aEEG and specific clinical morbidities is an important determinant of length of hospitalization among late-preterm infants.

Factors associated with initiation and exclusive breastfeeding at hospital discharge: late preterm compared to 37 week gestation mother and infant cohort

Background

To investigate and examine the factors associated with initiation of, and exclusive breastfeeding at hospital discharge of, late preterm (34 ^0/7 - 36 ^6/7 weeks) compared to 37 week gestation (37 ^0/7 - 37 ^6/7 week) mother and baby pairs.

Methods

A retrospective population-based cohort study using a Perinatal National Minimum Data Set and clinical medical records review, at the Royal Hobart Hospital, Tasmania, Australia in 2006.

Results

Late preterm and 37 week gestation infants had low rates of initiation of breastfeeding within one hour of birth, 31 (21.1%) and 61 (41.5%) respectively. After multiple regression analysis, late preterm infants were less likely to initiate breastfeeding within one hour of birth (OR 0.3 95% CI 0.1, 0.7 p = 0.009) and were less likely to be discharged exclusively breastfeeding from hospital (OR 0.4 95% CI 0.1, 1.0 p = 0.04) compared to 37 week gestation infants.

Conclusion

A late preterm birth is predictive of breastfeeding failure, with late preterm infants at greater risk of not initiating breastfeeding and/or exclusively breastfeeding at hospital discharge, compared with those infants born at 37 weeks gestation. Stratifying breastfeeding outcomes by gestational age groups may help to identify those sub-populations at greatest risk of premature cessation of breastfeeding.

NEONATAL OUTCOMES FOLLOWING LATE PRETERM BIRTH

It is well recognised that birth before 32 weeks of gestation is associated with substantial neonatal morbidity and mortality and these risks have been extensively reported. The focus of perinatal research for many years has therefore been very preterm and extremely preterm delivery, since the likelihood and severity of adverse neonatal outcomes are highest within this group. In contrast, until recently, more mature preterm infants have been understudied and indeed, almost ignored by researchers.

What we have here is a failure to communicate: obstacles to optimal care for preterm birth

Obstetricians and pediatricians share the common goal of a healthy beginning for every baby, mother, and family. This article asserts that miscommunication between the specialties, fostered by separate definitions, metrics, and outcomes, is an impediment to optimal care. Solutions are suggested for improving communication and outcomes.

Elective delivery at 34⁰(/)⁷ to 36⁶(/)⁷ weeks' gestation and its impact on neonatal outcomes in women with stable mild gestational hypertension

OBJECTIVE

To examine the frequency of elective delivery and neonatal outcomes in women with stable mild gestational hypertension delivering late preterm.

STUDY DESIGN

The frequency of elective delivery between 1995 and 2007 at gestational age of 34⁰(/)⁷-36⁶(/)⁷ weeks (late preterm), 37⁰(/)⁷-37⁶(/)⁷ weeks, and ≥38⁰(/)⁷ weeks, as well as neonatal outcomes, were studied in singleton gestation with mild gestational hypertension without proteinuria from a large national database.

RESULTS

One thousand eight hundred fifty-eight patients were studied: 607 (33%) were delivered for maternal/fetal reasons and 1251 (67%) were electively delivered. Among the 1251 women delivered electively, 25.5% were late preterm, 24.4% at 37⁰(/)⁷-37⁶(/)⁷ weeks and 50.1% at ≥38⁰(/)⁷ weeks' gestation. Neonatal intensive care unit admission, ventilatory assistance, and respiratory distress syndrome were more common in late-preterm infants. There was no maternal/perinatal mortality.

CONCLUSION

We found that 25.5% of patients with stable mild gestational hypertension, without any maternal or fetal complication, had iatrogenic elective late-preterm delivery. This practice also was associated with increased rates of neonatal complications and neonatal length of stay.

Respiratory morbidity and lung function in preterm infants of 32 to 36 weeks' gestational age

Normal lung development follows a series of orchestrated events. Premature birth interrupts normal in utero lung development, which results in significant alterations in lung function and physiology. Increasingly, there are reports documenting the broad range of complications experienced by infants aged 34 to 36 weeks' gestational age (GA). Our objective was to summarize the evidence demonstrating respiratory system vulnerability in infants aged 34 to 36 weeks' GA and to review the developmental and physiologic principles that underlie this vulnerability. A comprehensive search for studies that reported epidemiologic data and respiratory morbidity was conducted on the PubMed, Medline, Ovid Biosis, and Embase databases from 2000 to 2009 by using medical subject headings "morbidity in late preterm infants," "preterm infants and lung development," "prematurity and morbidity," and "prematurity and lung development." Because the number of studies exclusive to infants aged 34 to 36 weeks' GA was limited, selected studies also included infants aged 32 to 36 weeks' GA. Of the 24 studies identified, 16 were retrospective population-based cohort studies; 8 studies were observational. These studies consistently revealed that infants born at 32 to 36 weeks' GA, including infants of 34 to 36 weeks' GA, experience substantial respiratory morbidity compared with term infants. Levels of morbidity were, at times, comparable to those observed in very preterm infants. The developmental and physiologic mechanisms that underlie the increased morbidity rate and alterations in respiratory function are discussed. We also present evidence to demonstrate that the immaturity of the respiratory system of infants 34 to 36 weeks' GA at birth results in increased morbidity in infancy and leads to deficits in lung function that may persist into adulthood.

A statewide initiative to reduce inappropriate scheduled births at 36(0/7)-38(6/7) weeks' gestation

OBJECTIVE

We sought to reduce scheduled births between 36(0/7)-38(6/7) weeks that lack appropriate medical indication.

STUDY DESIGN

Twenty Ohio maternity hospitals collected baseline data for 60 days and then selected locally appropriate Institute for Healthcare Improvement Breakthrough Series interventions to reduce the incidence of scheduled births. Deidentified birth data were analyzed centrally. Rates of scheduled births without a documented indication, birth certificate data, and implementation issues were shared regularly among sites.

RESULTS

The rate of scheduled births between 36(0/7)-38(6/7) weeks without a documented medical indication declined from 25% to <5% (P < .05) in participating hospitals. Birth certificate data showed inductions without an indication declined from a mean of 13% to 8% (P < .0027). Dating criteria were documented in 99% of charts.

CONCLUSION

A statewide quality collaborative was associated with fewer scheduled births lacking a documented medical indication.

Indications for delivery and short-term neonatal outcomes in late preterm as compared with term births

OBJECTIVE

The objective of the study was to evaluate the indications for late preterm birth and compare outcomes by gestational age among late preterm (34-36 weeks) and term (> or = 37 weeks) neonates at our institution.

STUDY DESIGN

This was a retrospective analysis of delivery indications and short-term neonatal outcomes in women who delivered at the University Hospital between January 1, 2005 and Dec. 31, 2006. Data were analyzed using chi(2), Student's t-test, analysis of variance, and post hoc Tukey tests.

RESULTS

One hundred forty-nine late preterm (n = 49 for 34, n = 50 for 35, n = 50 for 36 weeks) and 150 term infants (n = 50 for 37, n = 50 for 38, n = 50 for 39 weeks or longer) were evaluated. Differences among groups (ie, 34 vs 35 vs 36 vs 37, etc) as well as combinations of differences between 2 groups (ie, 34-36 weeks vs > or = 37 or > or = 38 weeks) were analyzed. Spontaneous labor and/or rupture of membranes were the most common indications for late preterm delivery (92%). Compared with term, late preterm infants had longer hospital stays (5 days vs 2.4 days; P < .001) and higher rates of neonatal intensive care unit (NICU) admissions (56% vs 4%; P < .001), feeding problems (36% vs 5%; P < .001), hyperbilirubinemia (25% vs 3%; P < .001), and respiratory complications (20% vs 5%; P < .001). Neonatal complications were minimal at 38 weeks or longer.

CONCLUSION

Rates of neonatal intensive care unit admission, length of stay, and neonatal morbidities are significantly higher in late preterm as compared with term births.

Impact of cesarean section on intermediate and late preterm births: United States, 2000-2003

BACKGROUND

Cesarean section appears to be associated with increased risk of neonatal mortality among infants of low-risk term pregnancies, but it may offer some survival advantage among the most extremely preterm infants. The impact on intermediate (32-33 wk) and late preterm (34-36 wk) deliveries remains uncertain. The objective of this analysis was to compare the neonatal mortality rate (death at 0-27 days), the mechanical ventilation usage rate, and the incidence of hyaline membrane disease among intermediate and late preterm infants delivered by primary cesarean section compared with those delivered vaginally.

METHODS

United States Linked Birth and Infant Death Certificate files from the years 2000 to 2003 were used. Maternal demographic characteristics, medical complications, and labor and delivery complications were abstracted from the files along with infant information. Because of concern for misclassification of gestational age, a procedure was used to trim away births in which the birthweight of an infant for a specific gestational age was inconsistent. Adjusted odds ratios were calculated using logistic regression for the risk of the three outcomes of interest relative to the mode of delivery.

RESULTS

A total of 422,001 live births were available with complete data from the trimmed data set (60% of untrimmed data). After adjustment by logistic regression for infant size at birth, birthweight, sex, Apgar score at 5 minutes less than 4, multiple births, breech presentation, presence of an anomaly, the presence of any maternal medical condition or complication of labor and delivery, labor induction, maternal race, age, education, and gravidity, the adjusted odds ratios (95% CI for neonatal mortality at gestational ages of 32, 33, 34, 35, and 36 wk) were, respectively, 1.69 (1.31-2.20), 1.79 (1.40-2.29), 1.08 (0.83-1.40), 2.31 (1.78-3.00), and 1.98 (1.50-2.62).

CONCLUSIONS

These data suggest that for low-risk preterm infants at 32 to 36 weeks' gestation, independent of any reported risk factors, primary cesarean section may pose an increased risk of neonatal mortality and morbidity.