Umbilical Cord Blood as an Alternative to Neonatal Blood for Complete Blood Count: A Comparison Study.

OBJECTIVE: To assess concordance between umbilical cord blood (UCB) and neonatal blood (NB) laboratory test results at birth. STUDY DESIGN: This retrospective study considered very preterm neonates (<32 weeks' gestational age) admitted to a tertiary neonatal intensive care unit from 2012 to 2023. Inclusion criteria required neonates with a complete blood count measured in both UCB and NB drawn within 2 hours after birth. Median hemoglobin (Hb) and hematocrit (Hct) concentrations were compared between UCB (venous samples) and NB (venous, arterial, or capillary samples). RESULTS: A total of 432 neonates with paired UCB and NB values were included in the study. Hb concentration in UCB was 14.7 g/dL (IQR 13.5-16.1 g/dL) compared with 14.8 g/dL (IQR 12.6-19.3 g/dL) in venous NB samples, 13.9 g/dL (IQR 12.9-15.3 g/dL) in arterial NB and 18.7 g/dL (IQR 16.6-20.8 g/dL) in capillary NB. The regression equation showed a correction factor of 1.08 for converting Hb values from UCB to venous NB. Median Hct concentration in UCB was 0.45 L/L (IQR: 0.41-0.49 L/L) compared with 0.48 L/L (IQR 0.43-0.54 L/L) in venous NB, 0.42 L/L (IQR 0.38-0.45 L/L) in arterial NB and 0.57 L/L, (IQR 0.51-0.63 L/L) in capillary NB. CONCLUSIONS: Hb and Hct concentrations measured in UCB are similar to those measured in venous blood in very preterm infants and are valid alternatives for NB tests at birth. Hb and Hct concentrations in arterial and capillary NB are respectively lower and higher compared with UCB measurements.

Neonatal sepsis in alloimmune hemolytic disease of the fetus and newborn: A retrospective cohort study of 260 neonates.

BACKGROUND: Among neonates with hemolytic disease of the fetus and newborn (HDFN), we aimed to describe the frequency of central-line use, indications for insertion, and incidence of confirmed and suspected sepsis, including antibiotic treatment over a 10-year surveillance period. STUDY DESIGN AND METHODS: All neonates with HDFN admitted to our neonatal intensive care unit between January 2012 and December 2021 were included in this retrospective, cohort study. Annual proportions of infants with a central-line and central-line-associated bloodstream infection (CLABSI) rates (per 1000 central-line days and per 100 infants) were evaluated. Numbers of confirmed and suspected early- and late-onset sepsis episodes were assessed over the entire study period. RESULTS: Of the 260 included infants, 25 (9.6%) were evaluated for suspected sepsis, with 16 (6.2%) having ≥1 confirmed sepsis episode. A total of 123 central-lines were placed in 98 (37.7%) neonates, with impending exchange transfusion (ET) being the most frequent indication. Of the 34 (34.7%) neonates in whom a central-line was placed due to impending ET, 11 (32.4%) received no ET. Overall CLABSI incidence was 13.58 per 1000 central-line days. Neonates with a central-line had a higher risk for confirmed late-onset infection (RR 1.11, 95% CI: 1.04-1.20) and sepsis work-up (RR 1.10, 95% CI: 1.03-1.17) compared to infants without a central-line. CONCLUSIONS: Sepsis incidence among neonates with HDFN remains high, in particular in those with a central-line. Considering the substantial proportion of neonates with a central-line without eventual ET, central-line placement should be delayed until the likelihood of ET is high.

Developing a design-based concept to improve hand hygiene in the neonatal intensive care unit.

BACKGROUND: Hand hygiene (HH) is the most critical measure in the prevention of nosocomial infections in the neonatal intensive care unit (NICU). Improving and sustaining adequate HH compliance rates, however, remains a significant challenge. Using a behavioral change framework and nudge theory, we developed a design-based concept aimed at facilitating and stimulating HH behavior. METHODS: Concept development was initiated by selecting a theoretical framework after which contextual field studies aimed at discovering causes for poor compliance were conducted. Potential solutions were brainstormed upon during focus group sessions. Low-fidelity prototypes were tested regarding feasibility, usability, and acceptability. A final concept was crafted drawing from findings from each design phase. RESULTS: Complying with recommended HH guidelines is unrealistic and infeasible due to frequent competing (clinical) priorities requiring HH. The concept "Island-based nursing," where a patient room is divided into two geographical areas, namely, the island and general zone, was created. HH must be performed upon entering and exiting the island zone, and after exposure to any surface within the general zone. Reminding of HH is prompted by illuminated demarcation of the island zone, serving as the concept's nudge. CONCLUSIONS: Island zone demarcation facilitates and economizes HH indications in an innovative and intuitive manner. IMPACT: Although hand hygiene (HH) is the single most important element in the prevention of nosocomial infections in neonates, improving and sustaining adequate HH compliance rates remains a significant challenge. Complying with recommended HH guidelines was found to be unrealistic and infeasible due to the significant amount of time required for HH in a setting with a high workload and many competing (clinical) priorities. The concept of "Island-based nursing," under which the primary HH indication is upon entering and exiting the island zone, facilitates and economizes HH indications in an innovative and user-friendly manner.

Epigenetic Immune Cell Counting to Analyze Potential Biomarkers in Preterm Infants: A Proof of Principle in Necrotizing Enterocolitis.

Epigenetic immune cell counting is a DNA (de)methylation-based technique which can be used to quantify lymphocyte subsets on dried blood spots (DBS). The foregoing techniques allow for a retrospective investigation of immune cell profiles in newborns. In this study, we used this technique for determining lymphocyte subcounts as a potential biomarker for necrotizing enterocolitis (NEC). We investigated whether this technique can be implemented in the field of neonatology, by testing whether regulatory T cell (Treg) levels are pre-existently low in preterms with NEC. Newborn screening (NBS) cards from 32 preterms with NEC and 32 age- and weight-matched preterm controls, and 60 healthy term newborns, were analyzed. Relative and absolute cell counts were determined for CD3+, CD4+, CD8+, Th17, and Treg T cells. For both relative and absolute cell counts of CD3+, CD4+, CD8+, and Th17 T cells, significant differences were found between healthy term controls and both preterm groups, but not between preterm groups. For Tregs, no significant differences were found in either relative or absolute counts between any of the newborn groups. This study demonstrates the principle of epigenetic immune cell counting to analyze lymphocyte subsets in preterm neonates.

A longitudinal analysis of nosocomial bloodstream infections among preterm neonates.

Nosocomial bloodstream infections (NBSIs), commonly due to central-line associated bloodstream infections (CLABSI), contribute substantially to neonatal morbidity and mortality. We aimed to identify longitudinal changes in incidence of NBSI, microbiological-spectrum, and antibiotic exposure in a large cohort of preterm neonates admitted to the neonatal intensive care unit. We retrospectively assessed differences in annual rates of NBSI (per 1000 patient-days), CLABSI (per 1000 central-line days), and antibiotic consumption (per 1000 patient-days) among preterm neonates (< 32 weeks' gestation) hospitalized between January 2012 and December 2020. Multi-state Markov models were created to model states of progression of NBSI and infection risk given a central-line on days 0, 3, 7, and 10 of admission. Of 1547 preterm infants, 292 (19%) neonates acquired 310 NBSI episodes, 99 (32%) of which were attributed to a central-line. Over the years, a significant reduction in central-line use was observed (p < 0.001), although median dwell-time increased (p = 0.002). CLABSI incidence varied from 8.83 to 25.3 per 1000 central-line days, with no significant difference between years (p = 0.27). Coagulase-negative staphylococci accounted for 66% of infections. A significant decrease was found in antibiotic consumption (p < 0.001). Probability of NBSI decreased from 16% on day 3 to 6% on day 10. NBSI remains a common problem in preterm neonates. Overall antibiotic consumption decreased over time despite the absence of a significant reduction in infection rates. Further research aimed at reducing NBSI, in particular CLABSI, is warranted, particularly with regard to limiting central-line dwell-time and fine-tuning insertion and maintenance practices.

Regulatory T Cells in Development and Prediction of Necrotizing Enterocolitis in Preterm Neonates: A Scoping Review.

Necrotizing enterocolitis (NEC) is a leading cause of mortality in premature infants. However, the pathophysiology and influence of regulatory T cells (Tregs) have not been sufficiently elucidated. We performed a scoping review to investigate current knowledge on the influence of Tregs in NEC, and to investigate the predictive value of Treg number in NEC development. Pubmed, Embase, Prospero and Cochrane Library were searched during December 2020. Primary research articles discussing Tregs and NEC development written in English were selected. Two reviewers screened title and abstract for relevance, after which full-text screening was performed. A total of 20 articles were selected-13 of the articles discussed studies performed in animal models, while 8 used human neonate data. One study discussed both animal and human data. It was shown that after NEC diagnosis or induction, Treg levels were decreased while Th17 levels were increased. No studies were found which investigated the predictive value of Treg number in NEC development. A reduced Treg level is found in animals and neonates with NEC. The question remains whether this effect is a factor on the causal pathway of NEC development or a bystander effect. Future research focusing on the pathophysiological timeline of NEC and the involvement of Tregs is required for better understanding of this disease.

The road to zero nosocomial infections in neonates-a narrative review.

AIM: Nosocomial infections (NI) in neonates are associated with prolonged hospitalisation, adverse neurodevelopmental outcome and high mortality. Over the past decade, numerous prevention strategies have resulted in significant reductions in NI rates. In this review, we aim to provide an overview of current NI rates from large, geographically defined cohorts. METHODS: PubMed, Web of Science, EMBASE and Cochrane Library were searched for evidence regarding epidemiology and prevention of NI in neonates. Extracted studies were synthesised in a narrative form with experiential reflection. RESULTS: Despite the abundance of geographically defined incidence proportions, an epidemiological overview of NI is difficult to provide, given the lack of consensus definition for neonatal NI and different baseline populations being compared. Successful prevention efforts have focused on implementing evidence-based practices while eliminating outdated strategies. The most promising model for reduction in infection rates is based on quality improvement (QI) collaboratives and benchmarking, involving identification and implementation of best practices, selection of measurable outcomes and fostering a sense of community and transparency. CONCLUSION: The preventative rather than curative approach forms the new paradigm for reducing the burden of neonatal infections. Despite progress achieved, continued work towards improved prevention practices is required in the strive towards zero NIs.

Necrotizing enterocolitis in haemolytic disease of the newborn: a retrospective cohort study.

BACKGROUND AND OBJECTIVES: Necrotizing enterocolitis (NEC) is a common and often severe gastrointestinal emergency in newborn infants. While usually affecting (very) premature infants, an association between NEC and haemolytic disease of the foetus and newborn (HDFN) has been suggested. HDFN may be an additional risk factor to develop NEC. The objective of this study was to evaluate the occurrence of NEC in infants affected with moderate to severe HDFN in a large single centre cohort as compared to a broad population of infants without HDFN. MATERIALS AND METHODS: Retrospective cohort study of medical records of neonates with and without HDFN, with a gestational age at birth ≥30 weeks and ≤38 weeks, and admitted to the Leiden University Medical Center between January 2000 and December 2016. RESULTS: A total of 3284 patient records of infants born in the study period were reviewed and 317 cases of HDFN were identified. The incidence of NEC was significantly higher among infants with HDFN compared to infants without HDFN: 4/317 affected infants (1·3%) vs. 11/2967 affected infants (0·4%, relative risk 3·40, 95% confidence interval: 1·09-10·63). CONCLUSIONS: We observed a higher incidence of NEC in an overall late preterm to near term population of infants with moderate to severe HDFN, compared to infants born without HDFN. The clinician taking care of an HDFN-affected infant should be cautious of this higher risk.

Leukocyte Counts and Other Hematological Values in Twin-Twin Transfusion Syndrome and Twin Anemia-Polycythemia Sequence.

OBJECTIVE: The aim of this study was to evaluate the differences in leukocyte counts at birth between donors and recipients with twin-twin transfusion syndrome (TTTS) or twin anemia-polycythemia sequence (TAPS). METHODS: We performed a retrospective cohort study in monochorionic twin pairs with TTTS or TAPS. TTTS and TAPS cases treated with fetoscopic laser surgery were excluded. Primary outcome was the difference in leukocyte levels at birth between donor and recipient twins and the presence of leukopenia (defined as leukocyte count <4 × 109/L). Secondary outcomes included early-onset sepsis, necrotizing enterocolitis, use of antibiotics during admission, and neonatal mortality. RESULTS: We included 99 twins pairs, of which 61 twin pairs were affected by TAPS and 38 twin pairs by TTTS. The mean leukocyte count at birth in donors and recipients was 7.5 × 109/L versus 7.4 × 109/L (p = 0.936), respectively. Leukopenia was significantly more common in donor twins compared to recipient twins (7.1% [7/99] vs. 0% [0/99], p = 0.016). Of the 7 donors with leukopenia, 6 were affected by TAPS and 1 by TTTS. Overall, donors were more often affected by early-onset sepsis than recipients, 23.7% (23/97) versus 13% (13.7/95) (p = 0.049), respectively. CONCLUSIONS: Leukocyte counts at birth in twins with TTTS or TAPS are similar between donors and recipients, but TAPS donors are at an increased risk of leukopenia. Overall, TTTS and TAPS donors seem to be at an increased risk of early-onset neonatal sepsis compared to recipient twins.

Dynamics of the Gut Microbiota in Children Receiving Selective or Total Gut Decontamination Treatment during Hematopoietic Stem Cell Transplantation.

Bloodstream infections and graft-versus-host disease are common complications after hematopoietic stem cell transplantation (HSCT) procedures, associated with the gut microbiota that acts as a reservoir for opportunistic pathogens. Selective gut decontamination (SGD) and total gut decontamination (TGD) during HSCT have been associated with a decreased risk of developing these complications after transplantation. However, because studies have shown conflicting results, the use of these treatments remains subject of debate. In addition, their impact on the gut microbiota is not well studied. The aim of this study was to elucidate the dynamics of the microbiota during and after TGD and to compare these with the dynamics of SGD. In this prospective, observational, single-center study fecal samples were longitudinally collected from 19 children eligible for allogenic HSCT (TGD, n=12; SGD, n=7), weekly during hospital admission and monthly after discharge. In addition, fecal samples were collected from 3 family stem cell donors. Fecal microbiota structure of patients and donors was determined by 16S rRNA gene amplicon sequencing. Microbiota richness and diversity markedly decreased during SGD and TGD and gradually increased after cessation of decontamination treatment. During SGD, gut microbiota composition was relatively stable and dominated by Bacteroides, whereas it showed high inter- and intraindividual variation and low Bacteroides abundance during TGD. In some children TGD allowed the genera Enterococcus and Streptococcus to thrive during treatment. A gut microbiota dominated by Bacteroides was associated with increased predicted activity of several metabolic processes. Comparing the microbiota of recipients and their donors indicated that receiving an SCT did not alter the patient's microbiota to become more similar to that of its donor. Overall, our findings indicate that SGD and TGD affect gut microbiota structure in a treatment-specific manner. Whether these treatments affect clinical outcomes via interference with the gut microbiota needs to be further elucidated.

Restrictive guideline for red blood cell transfusions in preterm neonates: effect of a protocol change.

OBJECTIVE: To evaluate red blood cell (RBC) transfusion practices in preterm neonates before and after protocol change. METHODS: All preterm neonates (<32 weeks of gestation) admitted between 2008 and 2017 at our neonatal intensive care unit were included in this retrospective study. Since 2014, a more restrictive transfusion guideline was implemented in our unit. We compared transfusion practices before and after this guideline change. Primary outcome was the number of transfusions per neonate and the percentage of neonates receiving a blood transfusion. Secondary outcomes were neonatal morbidities and mortality during admission. RESULTS: The percentage of preterm neonates requiring a blood transfusion was 37·5% (405/1079) before and 32·7% (165/505) after the protocol change (P = 0·040). The mean number of transfusions given to each transfused neonate decreased from 2·93 (standard deviation (SD) ± 2·26) to 2·20 (SD ±1·29) (P = 0·007). We observed no association between changes in transfusion practices and neonatal outcome. CONCLUSION: The use of a more restrictive transfusion guideline leads to a reduction in red blood cell transfusions in preterm neonates, without evidence of an increase in mortality or short-term morbidity.

Risk Factors, Treatment, and Immune Dysregulation in Autoimmune Cytopenia after Allogeneic Hematopoietic Stem Cell Transplantation in Pediatric Patients.

Autoimmune or alloimmune cytopenia (AIC) is a known rare complication of hematopoietic stem cell transplantation (SCT). AIC after SCT is considered difficult to treat and is associated with high morbidity and mortality. In this retrospective study in pediatric patients we evaluated incidence, outcome, potential risk factors, and current treatment strategies. A nested matched case-control study was performed to search for biomarkers associated with AIC. Of 531 consecutive SCTs at our center between 2000 and 2016, 26 were complicated by the development of AIC (cumulative incidence, 5.0%) after a median of 5 months post-SCT. Autoimmune hemolytic anemia was the most common AIC with 12 patients (46%). We identified nonmalignant disease, alemtuzumab serotherapy pre-SCT, and cytomegalovirus (CMV) reactivation as independently associated risk factors. The cytokine profile of patients at the time of AIC diagnosis appeared to skew toward a more pronounced Th 2 response compared with control subjects at the corresponding time point post-SCT. Corticosteroids and intravenous immunoglobulin as first-line treatment or a wait-and-see approach led to resolution of AIC in 35% of cases. Addition of step-up therapies rituximab (n = 15), bortezomib (n = 7), or sirolimus (n = 3) was associated with AIC resolution in 40%, 57%, and 100% of cases, respectively. In summary, we identified CMV reactivation post-SCT as a new clinical risk factor for the development of AIC in children. The cytokine profile during AIC appears to favor a Th 2 response. Rituximab, bortezomib, and sirolimus are promising step-up treatment modalities.

Clinical implications of rapid ePlex® Respiratory Pathogen Panel testing compared to laboratory-developed real-time PCR.

Rapid diagnosis of respiratory infections is of great importance for adequate isolation and treatment. Due to the batch-wise testing, laboratory-developed real-time polymerase chain reaction (PCR) assays (LDT) often result in a time to result of one day. Here, LDT was compared with rapid ePlex® Respiratory Pathogen (RP) Panel testing of GenMark Diagnostics (Carlsbad, CA, USA) with regard to time to result, installed isolation precautions, and antibacterial/antiviral treatment. Between January and March 2017, 68 specimens of 64 patients suspected of an acute respiratory infection were tested with LDT and the ePlex® RP panel. The time to result was calculated as the time between sample reception and result reporting. Information regarding isolation and antibacterial/antiviral treatment was obtained from the patient records. Thirty specimens tested LDT positive (47%) and 29 ePlex® RP panel positive (45%). The median time to result was 27.1 h (range 6.5-96.6) for LDT versus 3.4 h (range 1.5-23.6) for the RP panel, p-value < 0.001. In 14 out of 30 patients, isolation was discontinued based on the ePlex® RP panel results, saving 21 isolation days. ePlex® RP panel test results were available approximately one day ahead of the LDT results in the 19 patients receiving antiviral/antibacterial treatment. In addition, two bacterial pathogens, not requested by the physician, were detected using the RP panel. Analysis of respiratory infections with the ePlex® RP panel resulted in a significant decrease in time to result, enabling a reduction in isolation days in half of the patients. Furthermore, syndromic RP panel testing increased the identification of causative pathogens.

Late-onset sepsis due to urinary tract infection in very preterm neonates is not uncommon.

Urinary tract infection (UTI) is a common cause of sepsis in infants. Premature infants hospitalized at a neonatal intensive care unit often have risk factors for infection. In this group, the risk of UTI is not clearly known, and guidelines for urine analysis are not unanimous. We aimed to identify the risk of UTI in premature infants with central lines, suspected of late-onset sepsis. We analyzed all 1402 infants admitted to our hospital between 2006 and 2014 with a gestational age less than 32 weeks. Six hundred sixty-two episodes of sepsis evaluations were found with an unknown source of infection based on clinical symptoms. In half of this group, urine analysis was performed identifying UTI in 11.3% (24/212). In 13 of these infants (54%) with a UTI, infection was due to Candida albicans. In at least four episodes, the diagnosis and treatment would have been delayed if urine analysis had not been performed. CONCLUSION: Based on these findings, we conclude that in premature infants with central lines, urine analysis should be performed routinely when signs of infection occur beyond 72 h after birth. Urine collection should not be delayed and cultures should preferably be performed before the start of the antibiotic treatment. What is known: • In preterm infants, the presence of other risk factors for infection might make clinicians reluctant to obtain urine cultures during sepsis evaluation. • An internal survey demonstrated that there is no consensus within the NICUs in The Netherlands regarding urine analysis as part of LOS work-up. What is new: • The risk of UTI in the NICU population (11.3%) is comparable to term infants; therefore, urine analysis should be performed routinely when LOS is suspected. • Candida albicans was the most frequently (54%) detected pathogen causing UTI in this population.

Deletion of the entire interferon-γ receptor 1 gene causing complete deficiency in three related patients.

PURPOSE: Complete interferon-γ receptor 1 (IFN-γR1) deficiency is a primary immunodeficiency causing predisposition to severe infection due to intracellular pathogens. Only 36 cases have been reported worldwide. The purpose of this article is to describe a large novel deletion found in 3 related cases, which resulted in the complete removal of the IFNGR1 gene. METHODS: Whole blood from three patients was stimulated with lipopolysaccharide (LPS) and IFN-γ to determine production of tumor necrosis factor (TNF), interleukin-12 p40 (IL-12p40) and IL-10. Expression of IFN-γR1 on the cell membrane of patients' monocytes was assessed using flow cytometry. IFNGR1 transcript was analyzed in RNA and the gene and adjacent regions were analyzed in DNA. Finally, IL22RA2 transcript levels were analyzed in whole blood cells and dendritic cells. RESULTS: There was no expression of the IFN-γR1 on the monocytes. Consistent with this finding, there was no IFN-γ response in the whole blood assay as measured by effect on LPS-induced IL-12p40, TNF and IL-10 production. A 119.227 nt homozygous deletion on chromosome 6q23.3 was identified, removing the IFNGR1 gene completely and ending 117 nt upstream of the transcription start of the IL22RA2 gene. Transcript levels of IL22RA2 were similar in patient and control. CONCLUSIONS: We identified the first large genomic deletion of IFNGR1 causing complete IFN-γR1 deficiency. Despite the deletion ending very close to the IL22RA2 gene, it does not appear to affect IL22RA2 transcription and, therefore, may not have any additional clinical consequence.

Increased Risk Of Early-Onset Neonatal Sepsis After Laser Surgery For Twin-to-Twin Transfusion Syndrome.

OBJECTIVE: To investigate the occurrence of early-onset neonatal sepsis (EOS) in twin-twin transfusion syndrome (TTTS) managed with laser surgery. STUDY DESIGN: We performed a prospective cohort study of all consecutive TTTS cases treated with laser surgery (TTTS group) delivered at the Leiden University Medical Center. We recorded the occurrence of EOS, defined as a positive blood culture ≤72 hours postpartum (proven sepsis) or administration of a full course of antibiotics due to risk factors or signs of sepsis, in the absence of a positive blood culture (suspected sepsis). Perinatal variables in the TTTS group were compared with uncomplicated monochorionic twins (no-TTTS group). A multivariate model was generated, examining the association between EOS and gestational age at birth, interval between laser surgery and birth, anterior placenta, laser period (first study period: 2002-2008; second study period: 2009-2015), and preterm premature rupture of membranes (PPROM). RESULTS: The rates of combined suspected and proven EOS in the TTTS group and no-TTTS group were 16% (68/416) and 10% (55/542), respectively (relative ratio [RR] 1.74, 95% confidence interval [CI] 1.19-2.55). Multivariate analysis showed that EOS in the TTTS group was independently associated with lower gestational age at birth (odds ratio [OR] 0.75, 95% CI 0.63-0.88), first study period (OR 2.25, 95% CI 1.08-4.67) and PPROM (OR 2.47, 95% CI 1.28-4.75). CONCLUSION: The rate of EOS in the TTTS group is low, but increased compared to the no-TTTS group. EOS in TTTS is independently associated with premature delivery, earlier laser period, and PPROM.

Necrotizing enterocolitis in monochorionic twins: Insights from an identical twin model.

Necrotizing enterocolitis (NEC) is a major cause of neonatal morbidity and mortality in preterm neonates, yet its pathophysiology remains unclear. The aim of this study is to evaluate risk factors for NEC using an identical twin model. In this case-control study, all monochorionic twin pairs born in our center in 2002-2020 were retrospectively reviewed for NEC. Potential risk factors for NEC were studied. For within-pair comparison, outcomes were compared between affected and unaffected twins. Within-pair analyses showed that the twin with NEC had a lower birth weight compared to its unaffected co-twin (1100 (913-1364) vs. 1339 (1093-1755) grams). Median gestational age at birth and birth weight were lower in twin pairs in the NEC-group compared to the no-NEC group, 29.1 weeks (27.8-30.8) versus 33.6 (30.7-36.0) and 1221 g (1010-1488) versus 1865 (1356-2355) respectively. Twin pregnancies in the NEC-group were more often complicated by twin-to-twin transfusion syndrome compared to the no-NEC-group (70 % (14/20) vs. 49 % (472/962)), particularly when treated with amnioreduction. This unique population of identical twins confirms that preterm neonates with a relatively lower birth weight are more prone to develop NEC compared to their co-twin, regardless of other genetic, maternal and obstetrical factors.