Preterm Morbidity Research Articles

Antenatal magnesium sulphate for fetal neuroprotection- A mini review.

Prematurity is one of the leading causes of neurological impairment and thus morbidity and mortality. Various preventive strategies are available to prevent preterm birth and fetal morbidity associated with prematurity. Magnesium sulphate was proposed for its benefits on fetal neuroprotection. Various randomised studies were done emphasising its use, the appropriate gestational age and dosing regimen. Hospital based protocols are required to implement its efficient usage.

Does Prepregnancy Weight or Maternal BMI at Betamethasone Administration Impact Late Preterm Respiratory Morbidity?

We sought to determine if maternal prepregnancy body mass index (BMI) is a risk factor for neonatal respiratory morbidity and to determine if increasing BMI decreased the efficacy of betamethasone (BMZ). This was a secondary analysis of the Antenatal Late Preterm Steroids trial, double-blind, randomized controlled trial involving 2,831 women between 340/7 and 365/7 weeks who received BMZ or a matching placebo. We compared the rate of neonatal respiratory morbidity among prepregnancy BMI classes in both the placebo and treatment groups. We also stratified the treatment effect by maternal BMI at the time of delivery. A total of 2,822 women were identified with maternal weight recorded at delivery; 2,740 women also had self-reported prepregnancy weight available. When stratified by prepregnancy BMI class, there was no difference in neonatal respiratory morbidity in the BMZ or in placebo groups. When analyzed by BMI at delivery, there was no difference in the rate of neonatal respiratory morbidity, and BMI was not a predictor of treatment response (odds ratio = 1.00, 95% confidence interval = 0.99-1.02). Maternal prepregnancy BMI is not associated with late preterm neonatal respiratory morbidity. Maternal obesity does not decrease the efficacy of BMZ for preventing late preterm neonatal respiratory morbidity.

Association of Maternal Preeclampsia with Neonatal Respiratory Distress Syndrome in Very-Low-Birth-Weight Infants

Preeclampsia is a common cause of preterm birth and neonatal morbidity, but its relationship with neonatal respiratory distress syndrome (RDS) remains controversial. We conducted a retrospective cohort study with data from very-low-birth-weight (VLBW) infants born in 1997–2014 from the database of the Premature Baby Foundation of Taiwan to evaluate the relationship between maternal preeclampsia and neonatal RDS. In total, 13,490 VLBW infants were enrolled, including 2200 (16.3%) infants born to preeclamptic mothers. The mean (standard deviation) gestational ages were 30.7 (2.5) weeks in the preeclamptic group and 28.6 (2.9) weeks in the control (non-preeclamptic) group. Severe RDS was defined according to the surfactant therapy requirement. The incidence of severe RDS was lower in infants exposed to maternal preeclampsia than in controls [28.9% vs. 44%; odds ratio (OR), 0.52; 95% confidence interval (CI), 0.47–0.57]. However, after adjustment for confounders, the OR for severe RDS development in the preeclampsia group was 1.16 (95% CI, 1.02–1.31). Other factors, such as gestational age, birth weight, female sex, and antenatal receipt of two or more steroid doses were significantly protective against RDS in multivariate regression analysis. This study revealed that maternal preeclampsia slightly increases the risk of severe RDS in VLBW infants.

The Impact of Severe Maternal Morbidity on Very Preterm Infant Outcomes

To estimate the prevalence of severe maternal morbidity among very preterm births and determine its association with very preterm infant mortality and morbidity. This study used New York City Vital Statistics birth and death records linked with maternal and newborn discharge abstract data for live births between 2010 and 2014. We included 6901 infants without congenital anomalies born between 240/7 and 326/7 weeks of gestation. Severe maternal morbidity was identified as life-threatening conditions or life-saving procedures. Outcomes were first-year infant mortality, severe neonatal morbidity (bronchopulmonary dysplasia, severe necrotizing enterocolitis, stage 3-5 retinopathy of prematurity, and intraventricular hemorrhage grades 3-4), and a combined outcome of death or morbidity. Twelve percent of very preterm live-born infants had a mother with severe maternal morbidity. Maternal and pregnancy characteristics associated with occurrence of severe maternal morbidity were multiparity, being non-Hispanic black, and preexisting health conditions, but gestational age and the percentage small for gestational age did not differ. Infants whose mothers experienced severe maternal morbidity had higher first-year mortality, 11.2% vs 7.7% without severe maternal morbidity, yielding a relative risk of 1.39 (95% CI: 1.14-1.70) after adjustment for maternal characteristics, preexisting comorbidities, pregnancy complications, and hospital factors. Severe neonatal morbidity was not associated with severe maternal morbidity. Severe maternal morbidity is an independent risk factor for mortality in the first year of life among very preterm infants after consideration of other maternal and pregnancy risk factors.

Early Enteral Administration of a Complex Lipid Emulsion Supplement Prevents Postnatal Deficits in Docosahexaenoic and Arachidonic Acids and Increases Tissue Accretion of Lipophilic Nutrients in Preterm Piglets.

Preterm delivery and current nutrition strategies result in deficiencies of critical long-chain fatty acids (FAs) and lipophilic nutrients, increasing the risk of preterm morbidities. We sought to determine the efficacy of preventing postnatal deficits in FAs and lipophilic nutrients using an enteral concentrated lipid supplement in preterm piglets. Preterm piglets were fed a baseline diet devoid of arachidonic acid (AA) and docosahexaenoic acid (DHA) and randomized to enteral supplementation as follows: (1) Intralipid (IL), (2) complex lipid supplement 1 (CLS1) with an AA:DHA ratio of 0.25, or (3) CLS2 with an AA:DHA ratio of 1.2. On day 8, plasma and tissue levels of FAs and lipophilic nutrients were measured and ileum histology performed. Plasma DHA levels decreased in the IL group by day 2. In contrast, DHA increased by day 2 compared with birth levels in both CLS1 and CLS2 groups. The IL and CLS1 groups demonstrated a continued decline in AA levels during the 8-day protocol, whereas AA levels in the CLS2 group on day 8 were comparable to birth levels. Preserving AA levels in the CLS2 group was associated with greater ileal villus height and muscular layer thickness. Lipophilic nutrients were effectively absorbed in plasma and tissues. Enteral administration of CLS1 and CLS2 demonstrated similar increases in DHA levels compared with birth levels. Only CLS2 maintained AA birth levels. Providing a concentrated complex lipid emulsion with an AA:DHA ratio > 1 is important in preventing postnatal AA deficits.

Preterm Clinical Co morbidity Index: A Novel Scoring System and Modeling for Predicting Length of Stay among Preterm Infants during Birth Hospitalization.

Preterm Clinical Co morbidity Index: A Novel Scoring System and Modeling for Predicting Length of Stay among Preterm Infants during Birth Hospitalization.

Study of chorioamnionitis among women with preterm birth at Ruhengeri referral hospital

Background: Chorioamnionitis is the association of microorganisms infection in fetal membrane, placental membrane and amniotic fluid. About 2 to 4% of chorioamnionitis occurs in full-term deliveries, but higher than this prevalence in preterm birth. Objectives: The objective of this study was to detect the most dominant bacteria of chorioamnionitis and evaluate correlation of the presence of microorganisms infection in placental membrane, fetal membrane and amniotic fluids in women with preterm birth. Methods: It was cross section study where 20 women with preterm premature rupture of membrane, premature rupture of membrane or preterm birth. By caesarean section or without caesarean section with a group of control of 10 women with term delivery. After delivery immediately the samples swab of amniotic fluid, fetal membrane and placenta membrane sample were placed in separate sterile container (swabs Stuart plastic) in the hospital, where it was stored at temperatures ranging between 8 oC-20 oC. Culture technique, gram staining and biochemical test were used to identify the microorganisms in this study at INES-Ruhengeri Microbiology laboratory. At the Ruhengeri Referral Hospital and analyzed according to INES Microbiology Laboratory standard operating procedures. Results: In 20 women with preterm birth, the most dominant microorganism was yeast 28.4% and mould 28.4%, other infections were caused by Escherichia coli, with 9.3%, Klebsiella species with 3.7%, Streptococcus species with 9.3%, Staphylococcus species with 9.3%, Candida albican with 11.7%. Those microorganisms show the association in fetal membrane, placenta membrane and amniotic fluid, of all women suspected to have chorioamnionitis. In 10 samples of control group, for women with term birth, same microorganisms were found like in fetal membrane were (Staphylococcus species 11%, mould 33%, and Yeast 56%), in placenta membrane were (Staphylococcus species 20%, mould 30%, Yeast 50%) and Amniotic fluid were (Staphylococcus species 0%, mould 33%, Yeast 67%). Conclusion: Chorioamnionitis can be in women with preterm birth or with term birth, untreated microorganism infections will cause a big problem of chorioamnionitis in pregnant women this will conduct to preterm morbidity and mortality.

Temporal Trends in Preterm Birth, Neonatal Mortality, and Neonatal Morbidity Following Spontaneous and Clinician-Initiated Delivery in Canada, 2009-2016.

Clinician-initiated deliveries at 34 to 36 weeks gestation have increased in Canada since 2006, but the impacts of clinician-initiated deliveries on the overall preterm birth (PTB) rate and concomitant changes in neonatal outcomes are unknown. This study examined gestational age-specific trends in spontaneous and clinician-initiated PTB and associated neonatal mortality and morbidity. This population-based study included 1880444 singleton live births in Canada (excluding Québec) in 2009-2016, using hospitalization data from the Canadian Institute for Health Information. The primary outcomes were neonatal mortality and a composite outcome mortality and/or severe neonatal morbidity identified by International Statistical Classification of Diseases and Related Health Problems, 10th revision, Canada codes. Outcomes were stratified by spontaneous and clinician-initiated deliveries and gestational age categories. Logistic regression yielded adjusted odds ratios (aORs) per 1-year change and 95% confidence intervals (CIs) (Canadian Task Force Classification II-2). The PTB rate remained stable (6.2%) and the proportion of clinician-initiated PTBs increased from 31.0% to 37.9% (P<0.001). Although overall neonatal mortality remained stable (1.1%), mortality declined among infants born spontaneously at 28 to 33 weeks gestation (aOR 0.92; 95% CI 0.87-0.97). The composite mortality and/or severe morbidity declined from 12.7% to 12.2% (aOR 0.98; 95% CI 0.97-0.99). Declines were observed in the rates of sepsis (aOR 0.96; 95% CI 0.95-0.98) and respiratory distress syndrome requiring ventilation (aOR 0.97; 95% CI 0.96-0.98), whereas rates of intraventricular hemorrhage increased (aOR 1.03; 95% CI 1.01-1.05). With the increase in clinician-initiated deliveries, the stable rates of PTB and neonatal mortality and the decline in composite mortality and/or severe morbidity are encouraging findings. This study adds to clinical understanding of carefully timed and medically justified early interventions.

Changes on preterm morbidities with antenatal magnesium

Purpose: The effect of magnesium sulphate (MgSO4) to mothers with imminent premature birth at &amp;lt;34 weeks on neonatal morbidities like intraventricular hemorrhage, feeding intolerance, retinopathy or bronchopulmoner dysplasia is not clear. We evaluated the effect of antenatal magnesium sulfate exposure on premature early and late morbidities and mortality retrospectively.Materials and Methods: 108 infants ≤ 32 gestational age having antenatal magnesium were grouped as Mg (+) and 172 infants ≤ 32 gestational age not having antenatal magnesium were grouped as Mg (-).Results: Respiratory Distress Syndrome, intraventricular hemorrhage, severe intraventricular hemorrhage (grade 3 and 4), retinopathy of prematurity and bronchopulmonary dysplasia were less in Mg (+) group compared to Mg (-) group but it is not statistically significant, except Respiratory Distress Syndrome.Conclusion: This retrospective study showed that ante natal exposure to MgSO4 did not have statistically significant beneficial effect on either morbidities or mortality in premature infants.

Prevalence and obstetric outcome of women with red cell antibodies in pregnancy at the Leeds Teaching Hospitals NHS Trust, West Yorkshire, England

ObjectiveThe prevalence of red cell antibodies in pregnancy varies with ethnicity and geographical location, while the obstetric outcome depends on the available standard of care. Despite being the tertiary fetal medicine centre in West Yorkshire, the prevalence of red cell antibodies, and the outcome of pregnancies associated with these antibodies at the Leeds University Teaching Hospitals Trust remains unreported. This article aims to provide this information for the purpose of patient education and counselling. Study designThe data of pregnant women with red cell antibodies between January 2011 and December 2016 was obtained from the Trust's database and reconciled with the Fetal Medicine Unit records using Viewpoint©. Fetal anaemia requiring in utero transfusion (IUT) was defined as a Middle Cerebral Artery Peak Systolic Velocities ≥ 1.5multiple of the median expected for gestational age. The mean gestational age at delivery, and perinatal outcomes of the pregnancies were recorded. ResultOverall, 398 of the 96, 692 pregnant women that were screened had red cell antibodies, giving a prevalence of 1: 242 pregnancies. The Anti- E and Anti-M antibodies were the most common (114 women; 28.6%, and 112 women; 28.1% respectively), but did not cause fetal anaemia in isolation, while anti-D alloimmunization was the predominant indication for in-utero transfusion (IUT). Anti-DE and anti-Kell antibodies had the highest mean number of transfusions per pregnancy. The mean gestational age at delivery was 34 ± 2weeks. Post-transfusion fetal demise was recorded in two hydropic fetuses, both at a gestational age of 25 weeks; giving a transfusion-related mortality rate of 2.5%. ConclusionThe prevalence of red cell antibodies at West Yorkshire is lower compared with reports from other Caucasian populations.Nevertheless, these antibodies are important causes of iatrogenic preterm delivery and fetal morbidity. The prognosis is however good with prompt diagnosis and management.

Association between Policy Changes for Oxygen Saturation Alarm Settings and Neonatal Morbidity and Mortality in Infants Born Very Preterm

To determine the impact of policy changes for pulse oximetry oxygen saturation (SpO2) alarm limits on neonatal mortality and morbidity among infants born very preterm. This was a retrospective cohort study of infants born very preterm in the Eunice Kennedy Shriver National Institute of Child Health and Human Development Neonatal Research Network. Infants were classified based on treatment at a hospital with an SpO2 alarm policy change and study epoch (before vs after policy change). We used a generalized linear mixed model to determine the effect of hospital group and epoch on the primary outcomes of mortality and severe retinopathy of prematurity (ROP) and secondary outcomes of necrotizing enterocolitis, bronchopulmonary dysplasia, and any ROP. There were 3809 infants in 10 hospitals with an SpO2 alarm policy change and 3685 infants in 9 hospitals without a policy change. The nature of most policy changes was to narrow the SpO2 alarm settings. Mortality was lower in hospitals without a policy change (aOR 0.63; 95% CI 0.50-0.80) but did not differ between epochs in policy change hospitals. The odds of bronchopulmonary dysplasia were greater for hospitals with a policy change (aOR 1.65; 95% CI 1.36-2.00) but did not differ for hospitals without a policy change. Severe ROP and necrotizing enterocolitis did not differ between epochs for either group. The adjusted odds of any ROP were lower in recent years in both hospital groups. Changing SpO2 alarm policies was not associated with reduced mortality or increased severe ROP among infants born very preterm.

Severe Modifications of Biological Markers in Late Neonatal Sepsis in a Very Low Birth Weight Due to Candida lusitaniae

Neonatal sepsis is a major cause of neonatal mortality and morbidity in preterm, very low birth weight infants. Coagulase-negative staphylococcus and Candida spp. are among the most common causes of single infections and coinfections in neonates. Candida lusitaniae is rarely reported as an opportunistic pathogen in very low birth weight neonates. Early diagnosis and appropriate antifungal therapy can prevent morbidity and mortality in preterms especially in coinfections. Necrotizing enterocolitis is one of the most catastrophic gastrointestinal emergencies in premature infants in the intensive care neonatal unit, especially in preterm infants. Currently, the pathogenesis of necrotizing enterocolitis is believed to have multifactorial causes. We present the case of a very low birth weight preterm who developed necrotizing enterocolitis and sepsis caused by a coinfection of Coagulase-negative Staphylococcus and Candida lusitaniae.

Turkish Neonatal Society guideline on the transfusion principles in newborns.

Blood transfusion can be defined as a life-saving procedure in neonates, especially in premature and surgical infants. The indications, threshold hemoglobin, and platelet levels for red cell, platelet, and plasma transfusions in neonates vary among centers and the evidence-based data for possible adverse effects, preterm morbidities, mortality, and neuro-developmental problems associated with transfusions are not clear yet. Herein, we aim to present the transfusion guideline designed to be used in neonatal intensive care units in our country, summarizing clinical findings and threshold levels for red cell, platelet, and plasma transfusions in addition to important practical points of transfusions according to a literature review.

Turkish Neonatal Society guideline on prevention and management of bronchopulmonary dysplasia.

Scientific and technological advances in perinatology and neonatology have led to an increased rate of survival and decreased incidences of various neonatal morbidities. However, the incidence of bronchopulmonary dysplasia has remained almost the same for years in very-low-birth-weight preterm infants. Although bronchopulmonary dysplasia is the leading cause of chronic respiratory morbidity in small preterms, no substantial improvement has been achieved in prevention and treatment strategies to date. Currently, postnatal very-low-dose corticosteroids, caffeine, and vitamin A seem to be the drugs of choice, and stem cell therapy appears to be the most promising treatment modality for the future. In this guideline, which was prepared by the Turkish Neonatal Society, recent evidence-based recommendations for the prevention and treatment of bronchopulmonary dysplasia are summarized.

Transabdominal cerclage for cervical insufficiency in twins: series of seven cases and literature review

Background: The diagnosis of cervical insufficiency is based on the previous history of recurrent second or early third trimester losses. Its incidence among pregnant women is 0.5–1% but can be as high as 75% among women with preterm birth. Transvaginal cerclage (TVC) is the common therapy of cervical insufficiency. However, this technique has several limits, especially in twin pregnancies. As some selected conditions, a transabdominal cerclage (TAC) is indicated, it has been offered to patients with multiple pregnancies.Aim: To evaluate the outcomes of twin pregnancies with transabdominal cerclage in terms of preterm birth rate and neonatal morbidity and mortality.Materials and methods: We conducted a retrospective study of seven patients with twin pregnancies managed with transabdominal cerclage at the end of the first trimester (12–15 weeks). We selected patients with a history of fetal loss who met the indications criteria of TAC (history of TVC failure or short cervix unable to have TVC). The antenatal and delivery data were collected and compared to those of their previous pregnancy.Outcomes: All patients carried their pregnancy throughout the second trimester and delivered during the third trimester. Mean gestational age was 34 4/7 week. All newborns were alive and neonatal morbidity rate was 50%, mostly related to preterm birth. Mean duration of neonatal intensive care stay was 32 days. There were no operative complications following TAC.Conclusions: Perinatal outcomes are considerably improved in twin pregnancies with transabdominal cerclage. Our findings corroborate those of previous case reports and support the efficacy of TAC for managing cervical insufficiency in twin pregnancies.

EQUIPTT: The Evaluation of the QUiPP app for Triage and Transfer protocol for a cluster randomised trial to evaluate the impact of the QUiPP app on inappropriate management for threatened preterm labour

BackgroundAccurate diagnosis of preterm labour is needed to ensure correct management of those most at risk of preterm birth and to prevent the maternal and fetal risks incurred by unnecessary interventions given to the large majority of women, who do not deliver within a week of presentation. Intervention “just-in-case” results in many avoidable admissions, women being transferred out of their local hospital unnecessarily and most women receiving unwarranted drugs, such as steroids and tocolytics. It also precludes appropriate transfers for others as neonatal cots are blocked pre-emptively, resulting in more dangerous ex-utero transfers. We have developed the QUiPP App which is a clinical decision-making aid based on previous outcomes of women, quantitative fetal fibronectin (qfFN) values and cervical length. It is hypothesised that using the QUiPP app will reduce inappropriate admissions and transfers.MethodsA multi-site cluster randomised trial will evaluate whether the QUiPP app reduces inappropriate management for threatened preterm labour. The 13 participating centres will be randomly allocated to receive either intervention or control. If the QUiPP app calculates risk of delivery within 7 days to be is less than 5%, clinicians are advised that interventions may be withheld. Women’s experience of threatened preterm labour assessment will be explored using self-completed questionnaires, with a subset of participants being invited to semi-structured interview. A health economics analysis is also planned.DiscussionWe hypothesise that the QUiPP app will improve identification of the most appropriate women for admission and transfer and ensure that therapies known to reduce risk of preterm neonatal morbidities are offered to those who need them. We will determine which women do not require these therapies, thereby reducing over-medicalisation and the associated maternal and fetal risks for these women. The findings will inform future national guidelines on threatened preterm labour. Beyond obstetrics, evaluating the impact of an app in an emergency setting, and our emphasis on balancing harms of over-treatment as well as under-treatment, make EQUIPTT a valuable contribution to translational medicine.Trial registrationThe EQUIPTT trial was prospectively registered on 16th January 2018 with the ISRCTN registry (no. 17846337).

The effects of omega-3 fatty acids on the newborn rat hyperoxic lung injury

Objective: Bronchopulmonary dysplasia (BPD) is an important cause of morbidity in preterms. Inflammation plays a central role in the pathogenesis of the disease while omega-3 fatty acids are known to have anti-inflammatory effects. In this study, we examined the effects of supplementary omega-3 fatty acids on hyperoxic lung injury.Methods: Experimental hyperoxic lung injury induced newborn 3-day-old rats were monitored in a confined hyperoxic environment with an oxygen concentration of 90–95% for a 2-week period. Rats were divided into three groups as placebo, low-dose Omega-3, and high-dose Omega-3. During the 2-week study period, low and high-dose Omega-3 groups were given 300 and 600 mg/kg/day omega-3 docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) respectively, while those in placebo received the same amount of serum physiologic. At the end of the 2-week study, lungs of all the rats were removed and morphologic evaluation under light microscopy was performed. Mean cord length (Lm), alveolar surface area (SA), and alveolar wall thickness (Wt) were calculated to find out whether a statistically significant difference between groups existed.Results: Similar alveolar development was observed between groups. No difference was seen between mean Lm values. Although the alveolar surface area was found to be higher in high-dose omega-3 group, the difference was not considered to be statistically significant. While the widest alveolar wall thickness was observed in the placebo group, alveolar wall thickness difference between high-dose omega-3 group and placebo group was found to be statistically significant (placebo Wt=17,8 ± 2.3 µm, low-dose omega −3 Wt=15,6 ± 2,5 µm, high-dose omega −3 Wt=14,2 ± 2 µm) (p < .05).Conclusions: Omega-3 fatty acids were observed to prevent alveolar wall thickness to some extent, though with no noticeable effect on hyperoxic lung injury.

The Effects of Antenatal Steroid Treatment on Preterm Infants' Early Laboratory Analysis.

Objectives:We assessed the effects of antenatal steroid treatment on preterm laboratory analysis conducted in the first 24 hours of life.Methods:Medical records of inborn preterm infants whose gestational age was ≤32 weeks were retrospectively reviewed in this study. Preterm infants whose mothers received antenatal betamethasone treatment of either 12 mg or 24 mg and who did not were divided into two groups. Maternal and neonatal demographic characteristics, all preterm morbidities and mortality rates, early laboratory examinations were compared between the two groups.Results:Medical records of 603 infants between 2008 and 2013 were retrospectively reviewed. Data from 515 infants were analyzed. Three hundred and four infants (n=304) were in the antenatal steroid treatment (AST) group and 211 infants were in the group that did not receive the treatment. The incidence of preeclampsia and oligohydramnios was significantly higher in the AST group. Intubation in the delivery room rates decreased in the AST group. APGAR scores at five minutes were significantly higher in the AST group. White blood counts (WBC) significantly decreased, whereas the platelet counts were higher in the AST group. Serum C-reactive protein (CRP) and Interleukin-6 (IL-6) levels did not differ between groups.Conclusion:We did not demonstrate any relationship between inflammatory markers and antenatal steroid treatment in preterm infants.

Initial Oxygen Use for Preterm Newborn Resuscitation: A Systematic Review With Meta-analysis.

This systematic review and meta-analysis provides the scientific summary of initial Fio2 in preterm newborns (<35 weeks' gestation) who receive respiratory support at birth. Medline, Embase, Evidence-Based Medicine Reviews, and Cumulative Index to Nursing and Allied Health Literature were searched between January 1, 1980 and August 10, 2018. Studies were selected by pairs of independent reviewers in 2 stages with a Cohen's κ of 0.8 and 1.0. Pairs of independent reviewers extracted data, appraised the risk of bias (RoB), and assessed Grading of Recommendations Assessment, Development and Evaluation certainty. Ten randomized controlled studies and 4 cohort studies included 5697 patients. There are no statistically significant benefits of or harms from starting with lower compared with higher Fio2 in short-term mortality (n = 968; risk ratio = 0.83 [95% confidence interval 0.50 to 1.37]), long-term mortality, neurodevelopmental impairment, or other key preterm morbidities. A sensitivity analysis in which 1 study with a high RoB was excluded failed to reveal a reduction in mortality with initial low Fio2 (n = 681; risk ratio = 0.63 [95% confidence interval 0.38 to 1.03]). The Grading of Recommendations Assessment, Development and Evaluation certainty of evidence was very low for all outcomes due to RoB, inconsistency, and imprecision. The ideal initial Fio2 for preterm newborns is still unknown, although the majority of newborns ≤32 weeks' gestation will require oxygen supplementation.

457: Does prepregnancy weight or maternal BMI at betamethasone administration impact late preterm respiratory morbidity?

457: Does prepregnancy weight or maternal BMI at betamethasone administration impact late preterm respiratory morbidity?