A multicenter prospective study of neonatal outcomes at less than 32 weeks associated with indications for maternal admission and delivery

Delivery indication matters for perinatal outcomes in late preterm newborns

BACKGROUND

The late preterm (LP) rate in Western countries is 3-6% of all births, accounting for about two-thirds of the entire preterm population. However, all LP babies are not the same.

AIMS

To identify pregnancies at risk for adverse outcomes in the LP period, we investigated how gestational age (GA) at delivery, delivery indication and prenatal risk factors may affect neonatal outcomes.

STUDY DESIGN

Prospective cohort study among singleton infants born between 34 + 0 and 36 + 6 weeks, in Emilia Romagna, Italy, during 2013-2015.

OUTCOMES MEASURES

The primary outcome was a composite of adverse perinatal outcomes. Multivariate logistic regression models were used to, respectively, investigate the effects of GA at delivery, circumstances at parturition and prenatal risk factors, on study outcomes after controlling for confounding variable.

RESULTS

Among 1867 births, 302, 504, and 1061 infants were born at 34, 35, and 36 weeks, respectively. There were no neonatal deaths. An increased risk of composite neonatal outcome was observed among 34 and 35 weeks deliveries compared with 36 weeks, and among indicated deliveries compared with spontaneous. When studying prenatal risk factors, neonatal morbidity was associated with pre gestational diabetes, preterm premature rupture of membranes (pPROM), maternal obesity, bleeding and polyhydramnios; instead, preeclampsia had a protective effect.

CONCLUSION

LP with indicated deliveries at 34 or 35 weeks, or with specific prenatal risk factors have worse neonatal outcome when compared to 36. Such differences should be considered when counseling patients and planning interventions such as timing of delivery in LP period.

Comparison of fetal lung maturation in fetuses with intrauterine growth restriction with control group, using lung volume, lung/liver and lung/muscle signal intensity and apparent diffusion coefficient ratios on different magnetic resonance imaging sequences

PURPOSE

To compare lung volume, lung apparent diffusion coefficient (ADC) and signal intensity ratio (SIR) on different magnetic resonance imaging (MRI) sequences between intrauterine growth restriction (IUGR) fetuses and the control group.

MATERIALS AND METHODS

49 IUGR and 58 non-IUGR fetuses were imaged using 3 Tesla MRI units. Total lung volume (TLV), lung/liver SIR (LLSIR) and lung/muscle SIR (LMSIR) in T1 and T2-weighted sequences and lung/liver ADC ratio (LLADCR) and lung/muscle ADC ratio (LMADCR) were assessed.

RESULTS

LLSIR and LMSIR were significantly higher in the T1-weighted sequence (p-value: .03) and LLADCR and LMADCR were significantly lower on diffusion-weighted imaging (DWI) in IUGR fetuses compared to the control group (p-value: .01). There was no significant difference in SIRs in the T2-weighted sequence between the two groups. Although TLV was increased with gestational age in both groups, it was significantly lower in the IUGR group (mean: 82 ± 22.7 ml vs. 110.8 ± 18 ml, p-value: <.001).

CONCLUSION

The T1-weighted sequence and DWI seem to be better than the T2-weighted sequence for assessing the faint difference of lung maturity between groups. However, SIR differences were not as meaningful as TLV differences and this could be related to the complex maturation process in IUGR fetuses as the effect of higher endogenous corticosteroids.

Cardiac function in fetal growth restriction

Fetal growth restriction (FGR) is defined as the inability of the fetus to reach its growth potential. According to the onset of the disease is defined early (<32 weeks) or late (≥32 weeks). FGR is associated with an increased risk of adverse short- and long-term outcomes, including hypoxemic events and neurodevelopmental delay compared to normally grown fetuses and increased risk of complications in the infanthood and adulthood. The underlying cause of FGR is placental insufficiency leading to chronic fetal hypoxia that affects cardiac hemodynamic with different mechanism in early and late onset growth restriction. In early onset FGR adaptive mechanisms involve the diversion of the cardiac output preferentially in favor of the brain and the heart, while abnormal arterial and venous flow manifest in the case of further worsening of fetal hypoxia. In late FGR the fetal heart shows a remodeling of its shape and function mainly related to a reduction of umbilical vein flow. In this review we discuss the modifications occurring at the level of the fetal cardiac hemodynamic in fetuses with early and late FGR.

Antenatal prediction models for short- and medium-term outcomes in preterm infants

INTRODUCTION

In extremely and very preterm infants, predicting individual risks for adverse outcomes antenatally is challenging but necessary for risk-stratified perinatal management and parents' participation in decision-making about treatment. Our aim was to develop and validate prediction models for short-term (neonatal period) and medium-term (3 years of age) outcomes based on antenatal maternal and fetal factors alone.

MATERIAL AND METHODS

A population-based study was conducted on 31 157 neonates weighing ≤1500 g and born between 22 and 31 weeks of gestation registered in the Neonatal Research Network of Japan during 2006-2015. Short-term outcomes were assessed in 31 157 infants and medium-term outcomes were assessed in 13 751 infants among the 31 157 infants. The clinical data were randomly divided into training and validation data sets in a ratio of 2:1. The prediction models were developed by factors selected using stepwise logistic regression from 12 antenatal maternal and fetal factors with the training data set. The number of factors incorporated into the model varied from 3 to 10, on the basis of each outcome. To evaluate predictive performance, the area under the receiver operating characteristics curve (AUROC) was calculated for each outcome with the validation data set.

RESULTS

Among short-term outcomes, AUROCs for in-hospital death, chronic lung disease, intraventricular hemorrhage (grade III or IV) and periventricular leukomalacia were 0.85 (95% CI 0.83-0.86), 0.80 (95% CI 0.79-0.81), 0.78 (95% CI 0.75-0.80), and 0.58 (95% CI 0.55-0.61), respectively. Among medium-term outcomes, AUROCs for cerebral palsy and developmental quotient of <70 at 3 years of age were 0.66 (95% CI 0.63-0.69) and 0.72 (95% CI 0.70-0.74), respectively.

CONCLUSIONS

Although the predictive performance of these models varied for each outcome, their discriminative ability for in-hospital death, chronic lung disease, and intraventricular hemorrhage (grade III or IV) was relatively good. We provided a bedside prediction tool for calculating the likelihood of various infant complications for clinical use. To develop these prediction models would be valuable in each country, and these risk assessment tools could facilitate risk-stratified perinatal management and parents' shared understanding of their infants' subsequent risks.

Cause of preterm birth and late-onset sepsis in very preterm infants: the EPIPAGE-2 cohort study

BACKGROUND

The pathogenesis of late-onset sepsis (LOS) in preterm infants is poorly understood and knowledge about risk factors, especially prenatal risk factors, is limited. This study aimed to assess the association between the cause of preterm birth and LOS in very preterm infants.

METHODS

2052 very preterm singletons from a national population-based cohort study alive at 72 h of life were included. Survival without LOS was compared by cause of preterm birth using survival analysis and Cox regression models.

RESULTS

437 (20.1%) had at least one episode of LOS. The frequency of LOS varied by cause of preterm birth: 17.1% for infants born after preterm labor, 17.9% after preterm premature rupture of membranes, 20.3% after a placental abruption, 20.3% after isolated hypertensive disorders, 27.5% after hypertensive disorders with fetal growth restriction (FGR), and 29.4% after isolated FGR. In multivariate analysis, when compared to infants born after preterm labor, the risk remained higher for infants born after hypertensive disorders (hazard ratio HR = 1.7, 95% CI = 1.2-2.5), hypertensive disorders with FGR (HR = 2.6, 95% CI = 1.9-3.6) and isolated FGR (HR = 2.9, 95% CI = 1.9-4.4).

CONCLUSION

Very preterm infants born after hypertensive disorders or born after FGR had an increased risk of LOS compared to those born after preterm labor.

IMPACT

Late-onset sepsis risk differs according to the cause of preterm birth. Compared with those born after preterm labor, infants born very preterm because of hypertensive disorders of pregnancy and/or fetal growth restriction display an increased risk for late-onset sepsis. Antenatal factors, in particular the full spectrum of causes leading to preterm birth, should be taken into consideration to better prevent and manage neonatal infectious morbidity and inform the parents.

Neonatal Morbidity and Mortality in Advanced Aged Mothers-Maternal Age Is Not an Independent Risk Factor for Infants Born Very Preterm

Background: As childbearing is postponed in developed countries, maternal age (MA) has increased over decades with an increasing number of pregnancies between age 35-39 and beyond. The aim of the study was to determine the influence of advanced (AMA) and very advanced maternal age (vAMA) on morbidity and mortality of very preterm (VPT) infants. Methods: This was a population-based cohort study including infants from the "Effective Perinatal Intensive Care in Europe" (EPICE) cohort. The EPICE database contains data of 10329 VPT infants of 8,928 mothers, including stillbirths and terminations of pregnancy. Births occurred in 19 regions in 11 European countries. The study included 7,607 live born infants without severe congenital anomalies. The principal exposure variable was MA at delivery. Infants were divided into three groups [reference 18-34 years, AMA 35-39 years and very(v) AMA ≥40 years]. Infant mortality was defined as in-hospital death before discharge home or into long-term pediatric care. The secondary outcome included a composite of mortality and/or any one of the following major neonatal morbidities: (1) moderate-to-severe bronchopulmonary dysplasia; (2) severe brain injury defined as intraventricular hemorrhage and/or cystic periventricular leukomalacia; (3) severe retinopathy of prematurity; and (4) severe necrotizing enterocolitis. Results: There was no significant difference between MA groups regarding the use of surfactant therapy, postnatal corticosteroids, rate of neonatal sepsis or PDA that needed pharmacological or surgical intervention. Infants of AMA/vAMA mothers required significantly less mechanical ventilation during NICU stay than infants born to non-AMA mothers, but there was no significant difference in length of mechanical ventilation and after stratification by gestational age group. Adverse neonatal outcomes in VPT infants born to AMA/vAMA mothers did not differ from infants born to mothers below the age of 35. Maternal age showed no influence on mortality in live-born VPT infants. Conclusion: Although AMA/vAMA mothers encountered greater pregnancy risk, the mortality and morbidity of VPT infants was independent of maternal age.

Neurodevelopment at 2 years and umbilical artery Doppler in cases of very preterm birth after prenatal hypertensive disorder or suspected fetal growth restriction: EPIPAGE-2 prospective population-based cohort study

OBJECTIVE

To investigate the association between absent or reversed end-diastolic flow (ARED) on umbilical artery Doppler ultrasound and poor neurological outcome at 2 years of age after very preterm birth associated with suspected fetal growth restriction (FGR) or maternal hypertensive disorders.

METHODS

The study population comprised all very preterm (22-31 completed weeks) singleton pregnancies delivered because of suspected FGR and/or maternal hypertensive disorders that had umbilical artery Doppler and 2-year follow-up available included in EPIPAGE-2, a prospective, nationwide, population-based cohort of preterm births in France in 2011. Univariate and two-level multivariable logistic regression analyses were used to assess the association of ARED in the umbilical artery, as compared with normal or reduced end-diastolic flow, with severe or moderate neuromotor and/or sensory disability and with an Ages and Stages Questionnaire (ASQ) score below a threshold. This was defined as a score more than 2 SD below the mean in any of the five domains, at age 2, adjusting for gestational age at delivery. ASQ is used to identify children at risk of developmental delay requiring reinforced follow-up and further evaluation. Descriptive statistics and bivariate tests were weighted according to the duration of the inclusion periods.

RESULTS

The analysis included 484 children followed up at 2 years of age, for whom prenatal umbilical artery Doppler ultrasound was available. Among them, 8/484 (1.6%) had severe or moderate neuromotor and/or sensory disability, and 156/342 (45.4%) had an ASQ score below the threshold. Compared with normal or reduced end-diastolic flow in the umbilical artery (n = 305), ARED (n = 179) was associated with severe or moderate neuromotor and/or sensory disability (adjusted odds ratio (OR), 11.3; 95% CI, 1.4-93.2) but not with an ASQ score below the threshold (adjusted OR, 1.2; 95% CI, 0.8-1.9).

CONCLUSION

Among children delivered before 32 weeks of gestation due to suspected FGR and/or maternal hypertensive disorder who survived until 2 years of age, prenatal ARED in the umbilical artery was associated with a higher incidence of severe or moderate neuromotor and/or sensory disability. Copyright © 2020 ISUOG. Published by John Wiley & Sons Ltd.

A new rapid bedside test to diagnose and monitor intraamniotic inflammation in preterm PROM using transcervically collected fluid

BACKGROUND

Microbial invasion of the amniotic cavity, a clinical condition present in approximately 50% of patients with preterm prelabor rupture of membranes, is often associated with intraamniotic inflammation, a risk factor for a short admission-to-delivery interval, early preterm delivery, and neonatal complications. We previously developed a transcervical amniotic fluid collector, the device that allows the collection of fluid noninvasively from the cervical canal when membrane rupture occurs.

OBJECTIVE

This study was designed to determine whether rapid analysis of an interleukin-8 concentration in fluid obtained noninvasively by the transcervical amniotic fluid collector can be used to assess the risk of intraamniotic inflammation. We also compared the diagnostic performance of this point-of-care test for interleukin-8 in transcervically obtained fluid to that of a white blood cell count determined in amniotic fluid retrieved by transabdominal amniocentesis.

STUDY DESIGN

This prospective cohort study was conducted between October 2011 and April 2017. Fluid was retrieved through both transabdominal amniocentesis and the use of a transcervical amniotic fluid collector within 24 hours of amniocentesis in patients with a singleton pregnancy and preterm prelabor rupture of the membranes (16-35 weeks of gestation). Amniotic fluid obtained via amniocentesis was cultured for aerobic and anaerobic bacteria and genital mycoplasmas; a white blood cell count was also measured in amniotic fluid. Intraamniotic infection was diagnosed when microorganisms were identified by the cultivation of amniotic fluid. Intraamniotic inflammation was defined as an elevated amniotic fluid matrix metalloproteinase-8 concentration (>23 ng/mL) assayed by enzyme-linked immunosorbent assay. Interleukin-8 in cervical fluid obtained by the collector was measured by the point-of-care test that used a test strip and scanner based on the fluorescence immunochromatographic analysis in 2019. The diagnostic indices, predictive values, and likelihood ratios of the 2 different tests were calculated.

RESULTS

First, interleukin-8 concentration ≥9.5 ng/mL in cervical fluid, determined by the point-of-care test, was at the knee of the receiver operating characteristic curve analysis and had a sensitivity of 98% (56/57; 95% confidence interval, 91-99.96%), specificity of 74% (40/54; 95% confidence interval, 60-85%), positive predictive value of 80% (56/70; 95% confidence interval, 72-86%), negative predictive value of 98% (40/41; 95% confidence interval, 85-99.6%), positive likelihood ratio of 3.79 (95% confidence interval, 2.41-5.96), and negative likelihood ratio of 0.02 (95% confidence interval, 0.003-0.17) in the identification of intraamniotic inflammation; a concentration of matrix metalloproteinase-8 >23 ng/mL by enzyme-linked immunosorbent assay had a prevalence of 51% (57/111). Second, a cervical fluid interleukin-8 concentration ≥9.5 ng/mL had significantly higher sensitivity than a transabdominally obtained amniotic fluid white blood cell count (≥19 cells/mm³) in the identification of intraamniotic inflammation (sensitivity: 98% [95% confidence interval, 91-99.96%] vs 84% [95% confidence interval, 72-93%]; P<.05; specificity: 74% [95% confidence interval, 60-85%] vs 76% [95% confidence interval, 62-87%); positive and negative predictive values: 80% [95% confidence interval, 72-86%] and 98% [95% confidence interval, 85-99.6%] vs 79% [95% confidence interval, 69-86%] and 82% [95% confidence interval, 71-89%]) and in the identification of intraamniotic inflammation/infection (gold standard: positive culture for bacteria or a matrix metalloproteinase-8 >23 ng/mL; sensitivity: 91% [95% confidence interval, 82-97%] vs 75% [95% confidence interval, 63-85%]; P<.05).

CONCLUSION

The point-of-care test was predictive of intraamniotic inflammation, based on the determination of interleukin-8 in fluid retrieved by a transcervical amniotic fluid collector. Therefore, the analysis of cervically obtained fluid by such point-of-care test may be used to noninvasively monitor intraamniotic inflammation in patients with preterm prelabor rupture of membranes.

Obstetrical characteristics and neonatal outcome according to aetiology of preterm birth: a cohort study

PURPOSE

Preterm birth (PTB) can be categorised according to aetiology into: spontaneous preterm labour (SPL), preterm prelabour rupture of membranes (PPROM), and iatrogenic (iatro) PTB. Outcomes could differ between these groups, which could be of interest in counselling. We aimed to explore differences between aetiologic groups of PTB in maternal demographics, obstetrical characteristics and management, and neonatal outcomes.

METHODS

This is a cohort study (2012-2018) in Ghent University Hospital, Belgium, of deliveries from 24 + 0 to 33 + 6 weeks. We compared perinatal demographics, management, and outcomes between the aetiologic types of PTB. Point and interval estimates for differences between aetiologic types were estimated using a Generalised Estimating Equations approach to handle clustering due to multiple gestations.

RESULTS

813 mothers and 987 neonates were included. Prevalences of different aetiologic types of PTB were similar. Maternal BMI was higher in the iatrogenic group (iatro-SPL: + 1.92 kg/m², 95% CI 1.02, 2.83; iatro-PPROM: + 2.06 kg/m², 95% CI 1.15, 2.96). There was an inversed sex ratio (0.82, 95% CI 0.65, 1.03), more growth restriction (iatro-SPL: + 22.60%, 95% CI 17.08, 28.13; iatro-PPROM: + 24.64%, 95% CI 19.44, 29.83), and a higher caesarean section rate in the iatrogenic group (iatro-SPL: + 57.23%, 95% CI 50.32, 64.13, iatro-PPROM: + 56.79%, 95% CI 50.20, 63.38) and more patients received at least one complete course of antenatal corticosteroids (iatro-SPL: + 17.60%, 95% CI 10.60, 24.60, iatro-PPROM: + 10.73%, 95% CI 4.52, 16.94). In all types of PTB, adverse neonatal outcomes had a low prevalence, except for respiratory distress syndrome. A composite of adverse neonatal outcome was more prevalent in the SPL- compared to the PPROM group, and there was less intraventricular haemorrhage in the iatrogenic group.

CONCLUSION

Additional to gestational age at birth, the aetiology of PTB is associated with neonatal outcome. More data are needed to enable individualised management and counselling in case of threatened PTB.

TRIAL REGISTRATION NUMBER

NCT03405116.

Risk Factors for Neonatal Mortality in Preterm Newborns in The Extreme South of Brazil

Neonatal mortality still remains a complex challenge to be addressed. In Brazil, 60% of neonatal deaths occur among preterm infants with a gestational age of 32 weeks or less (≤32w). The aim of this study was to evaluate the factors involved in the high mortality rates among newborns with a gestational age ≤32w in a socioeconomically developed southern city in Brazil. Data on retrospective births and deaths (2000-2014) were analyzed from two official Brazilian national databases. The risk of neonatal death for all independent variables (mother's age and schooling, prenatal visits, birth hospital, delivery method, gestational age, and the newborn's sex, age, and birth year, gemelarity, congenital anomalies and birthplace) was assessed with a univariable and a multivariable model of Cox's semiparametric proportional hazards regression (p < 0.05). Data of 288,904 newborns were included, being 4,514 with a gestational age ≤32w. The proportion of these early newborns remained stable among all births, while the neonatal mortality rate for this group tended to decrease (p < 0.001). The adjusted risk was significantly for lower birthweight infants (mean 659.13 g) born from Caesarean (HR 0.58 [95% CI 0.47-0.71]), but it was significantly higher for heavier birth weight infants (mean 2,087.79) also born via Caesarean section (HR 3.71 [95% CI 1.5-9.15]). Newborns with lower weight seemed to benefit most from Cesarean deliveries. Effort towards reducing unacceptably high surgical deliveries must take into account cases that the operations may be lifesaving for mother and/or the baby.

Neonatal Outcome After Preeclampsia and HELLP Syndrome: A Population-Based Cohort Study in Germany

Aim: To analyze short term outcomes of very low birth weight infants (VLBWI) born preterm after maternal preeclampsia and HELLP syndrome within the German Neonatal Network. Methods: The German Neonatal Network is a large population-based cohort study enrolling VLBWI since 2009. Two thousand six hundred and fifty two infants below 32 weeks of gestation born after maternal preeclampsia or HELLP syndrome and 13,383 infants born prematurely for other causes between 2009 and 2018 were included in our analysis. Descriptive statistics and multinomial regression models including preeclampsia and HELLP syndrome were performed for short-term outcome measures such as intracerebral hemorrhage, necrotizing enterocolitis requiring surgery, bronchopulmonary dysplasia, retinopathy of prematurity, periventricular leukomalacia, persistent ductus arteriosus requiring surgery, blood culture positive sepsis and death. Results: After adjustment for confounding variables, preterm birth due to preeclampsia or HELLP syndrome was associated with a reduced risk for intracerebral hemorrhage (OR 0.73, 95% CI 0.60-0.89), necrotizing enterocolitis requiring surgery (OR 0.35 95% CI 0.15-0.82), periventricular leukomalacia (OR 0.61 95% CI 0.40-0.92), and death (OR 0.72 95% CI 0.55-0.96) as compared to other causes of preterm birth. Conclusions: The indication for preterm birth has an impact on neonatal outcome in preterm infants born below 32 weeks. This notion should be included when counseling the families.

Preterm infants with peri/intraventricular hemorrhage have poorer habituation responses to external stimuli

OBJECTIVE

To evaluate the association between intra-ventricular hemorrhage and habituation responses to external stimuli in preterm infants at 36-38 weeks post-conceptual age.

METHODS

Cross-sectional study of infants with gestational age <32 weeks. Intra-ventricular hemorrhage was identified by cranial ultrasonography and classified according to Papile et al. (1978). The luminous (flashlight), sound (rattle, bell), and tactile stimuli were presented, and the responses were scored according to Lester and Tronik (2004). Habituation response scores were compared between groups by Student's t-test. The association between IVH and habituation scores was evaluated by linear regression adjusted for GA, clinical severity score, post-conceptual age at habituation assessment, sepsis, and bronchopulmonary dysplasia.

RESULTS

Sixty-five infants were studied, 20 with intra-ventricular hemorrhage (16 grades I/II; four grades III/IV) and 45 without intra-ventricular hemorrhage. Infants with intra-ventricular hemorrhage had lower gestational age (28.2±2.2 vs. 29.7±1.7 weeks) and birth weight (990±305 vs. 1275±360g). Infants with intra-ventricular hemorrhage at 36-38 weeks post-conceptual age had lower habituation scores to light (4.21±2.23 vs. 6.09±2.44), rattle (3.84±2.12 vs. 6.18±2.27), and bell (3.58±1.74 vs. 5.20±2.47) after controlling for confounders. No differences were found for tactile stimulus.

CONCLUSION

Infants with gestational age <32 weeks and intra-ventricular hemorrhage had poorer habituation responses to external stimuli than those without intra-ventricular hemorrhage at 36-38 weeks post-conceptual age.

Epidemiological profile of patients with preterm premature rupture of membranes at a tertiary hospital in São Paulo, Brazil

OBJECTIVE

To perform a descriptive analysis of preterm premature rupture of membranes (PPROM) cases attended in a tertiary hospital.

METHOD

Retrospective analysis of medical records and laboratory tests of patients admitted to a Brazilian tertiary hospital between 2006 and 2011, with a confirmed diagnosis of PPROM and gestational age (GA) at delivery <37 weeks.

RESULTS

A total of 299 pregnant women were included in the study. Nine patients evolved to abortion, and 290 pregnant women remained for the final analysis. There was initial diagnostic doubt in 17.6% of the cases. The oligohydramnios rate [amniotic fluid index (AFI) <5] was 27.9% on admission. Chorioamnionitis was initially diagnosed in 10.8% of the patients and was retrospectively confirmed in 22.9% of the samples. The latency period had a mean of 9.1 days. The main reasons for interruption were premature labor (55.2%), GA ≥36 weeks (27.2%), and fetal distress (6.9%). The delivery method was cesarean section in 55% of cases. The mean birth weight was 2,124 grams, and 67% of the neonates had a low birth weight (<2500 g). The GA at delivery averaged 33.5 weeks. The stillbirth rate was 5.3%, and the early neonatal mortality rate was 5.6%. There were complications at delivery in 18% of mothers.

CONCLUSION

In one of the few Brazilian reports on the epidemiological profile of PPROM, with GA until 37 weeks and intercurrences generally excluded from assessments (such as twinning and fetal malformations), there is a favorable evolution, with an acceptable rate of complications.

Estimating risk of severe neonatal morbidity in preterm births under 32 weeks of gestation

Background: A large recent study analyzed the relationship between multiple factors and neonatal outcome and in preterm births. Study variables included the reason for admission, indication for delivery, optimal steroid use, gestational age, and other potential prognostic factors. Using stepwise multivariable analysis, the only two variables independently associated with serious neonatal morbidity were gestational age and the presence of suspected intrauterine growth restriction as a reason for admission. This finding was surprising given the beneficial effects of antenatal steroids and hazards associated with some causes of preterm birth. Multivariable logistic regression techniques have limitations. Without testing for multiple interactions, linear regression will identify only individual factors with the strongest independent relationship to the outcome for the entire study group. There may not be a single "best set" of risk factors or one set that applies equally well to all subgroups. In contrast, machine learning techniques find the most predictive groupings of factors based on their frequency and strength of association, with no attempt to identify independence and no assumptions about linear relationships.Objective: To determine if machine learning techniques would identify specific clusters of conditions with different probability estimates for severe neonatal morbidity and to compare these findings to those based on the original multivariable analysis.Materials and methods: This was a secondary analysis of data collected in a multicenter, prospective study on all admissions to the neonatal intensive care unit between 2013 and 2015 in 10 hospitals. We included all patients with a singleton, stillborn, or live newborns, with a gestational age between 23 0/7 and 31 6/7 week. The composite endpoint, severe neonatal morbidity, defined by the presence of any of five outcomes: death, grade 3 or 4 intraventricular hemorrhage (IVH), and ≥28 days on ventilator, periventricular leukomalacia (PVL), or stage III necrotizing enterocolitis (NEC), was present in 238 of the 1039 study patients. We studied five explanatory variables: maternal age, parity, gestational age, admission reason, and status with respect to antenatal steroid administration. We concentrated on Classification and Regression Trees because the resulting structure defines clusters of risk factors that often bear resemblance to clinical reasoning. Model performance was measured using area under the receiver-operator characteristic curves (AUC) based on 10 repetitions of 10-fold cross-validation.Results: A hybrid technique using a combination of logistic regression and Classification and Regression Trees had a mean cross-validated AUC of 0.853. A selected point on its receiver-operator characteristic (ROC) curve corresponding to a sensitivity of 81% was associated with a specificity of 76%. Rather than a single curve representing the general relationship between gestational age and severe morbidity, this technique found seven clusters with distinct curves. Abnormal fetal testing as a reason for admission with or without growth restriction and incomplete steroid administration would place a 20-year-old patient on the highest risk curve.Conclusions: Using a relatively small database and a few simple factors known before birth it is possible to produce a more tailored estimate of the risk for severe neonatal morbidity on which clinicians can superimpose their medical judgment, experience, and intuition.

Outcomes of Medically Indicated Preterm Births Differ by Indication

OBJECTIVE

We aim to examine whether outcomes of preterm birth (PTB) are further modified by the indication for delivery.

STUDY DESIGN

We performed a retrospective cohort study of all singletons delivered at 23 to 34 weeks from 2011 to 2014. Women were classified by their primary indication for delivery: maternal (preeclampsia) or fetal/obstetric (growth restriction, nonreassuring fetal status, and vaginal bleeding). The primary neonatal outcome was a composite of neonatal death, cord pH <7 or base excess < - 12, 5-minute Apgar ≤3, C-reactive protein during resuscitation, culture-proven sepsis, intraventricular hemorrhage, and necrotizing enterocolitis. Secondary outcomes included the individual components of the primary outcome. Groups were compared using Student's t-test and chi-squared tests. Logistic regression was used to adjust for confounding variables.

RESULTS

Of 528 women, 395 (74.8%) were delivered for maternal and 133 (25.2%) for fetal/obstetric indications. Compared with those delivered for a maternal indication, those with a fetal/obstetric indication for delivery had an increased risk of the composite neonatal outcome (adjusted odds ratio [AOR]: 1.9, 95% confidence interval [CI]: 1.13-3.21) and acidemia at birth (AOR: 4.2, 95% CI: 1.89-9.55).

CONCLUSION

Preterm infants delivered for fetal/obstetric indications have worsened outcomes compared with those delivered for maternal indications. Additional research is needed to further tailor counseling specific to the indication for delivery.