To explore the impact of COVID-19 lockdown on premature birth rates in Denmark, a nationwide register-based prevalence proportion study was conducted on all 31 180 live singleton infants born in Denmark between 12 March and 14 April during 2015–2020.The distribution of gestational ages (GAs) was significantly different (p=0.004) during the lockdown period compared with the previous 5 years and was driven by a significantly lower rate of extremely premature children during the lockdown compared with the corresponding mean rate for the same dates in the previous years (OR 0.09, 95% CI 0.01 to 0.40, p<0.001). No significant difference between the lockdown and previous years was found for other GA categories.The reasons for this decrease are unclear. However, the lockdown has provided a unique opportunity to examine possible factors related to prematurity. Identification of possible causal mechanisms might stimulate changes in clinical practice.

BackgroundDyslipidemia is reported in 27 − 43% of children and adolescents with overweight/obesity and tracks into adulthood, increasing the risk of cardiovascular morbidity. Cut-off values for fasting plasma lipid concentrations are typically set at fixed levels throughout childhood. The objective of this cross-sectional study was to generate fasting plasma lipid references for a Danish/North-European White population-based cohort of children and adolescents, and investigate the prevalence of dyslipidemia in this cohort as well as in a cohort with overweight/obesity.MethodsA population-based cohort of 2141 (1275 girls) children and adolescents aged 6 − 19 (median 11.5) years was recruited from 11 municipalities in Denmark. Additionally, a cohort of children and adolescents of 1421 (774 girls) with overweight/obesity aged 6 − 19 years (median 11.8) was recruited for the study. Height, weight, and fasting plasma lipid concentrations were measured on all participants. Smoothed reference curves and percentiles were generated using the Generalized Additive Models for Location Scale and Shape package in the statistical software R.ResultsIn the population-based cohort, plasma concentrations of total cholesterol (TC) (P < 0.05), low-density lipoprotein cholesterol (LDL) (P < 0.005), and high-density lipoprotein cholesterol (HDL) (P < 0.005) were higher in the youngest compared to the oldest tertile. Fasting plasma levels of triglycerides (TG) (P < 0.005) increased with age in both sexes. In boys, non-HDL was lower in the oldest compared to the youngest tertile (P < 0.0005).Concentrations of TC, LDL, non-HDL, and TG were higher (P < 0.05), and HDL lower (P < 0.05) in the cohort with overweight/obesity in both sexes and for all ages except for TC in the youngest girls. The overall prevalence of dyslipidemia was 6.4% in the population-based cohort and 28.0% in the cohort with overweight/obesity. The odds ratio for exhibiting dyslipidemia in the cohort with overweight/obesity compared with the population-based cohort was 6.2 (95% CI: 4.9 − 8.1, P < 2*10−16).ConclusionFasting plasma lipid concentrations change during childhood and adolescence and differ with sex and age. Children and adolescents with obesity have increased concentrations of circulating lipids and exhibit an increased prevalence of dyslipidemia.Trial registrationThe study is part of The Danish Childhood Obesity Biobank; ClinicalTrials.gov ID-no.: NCT00928473 retrospectively registered on June 25th 2009.Electronic supplementary materialThe online version of this article (doi:10.1186/s12887-017-0868-y) contains supplementary material, which is available to authorized users.

t(12;21)(p13;q22)[ETV6-RUNX1] is the most common chromosomal translocation in childhood acute lymphoblastic leukemia, and it can often be backtracked to Guthrie cards supporting prenatal initiation and high levels of circulating t(12;21)-positive cells at birth. To explore the prevalence of ETV6-RUNX1-positive cells in healthy neonates, mononuclear cells from 1417 umbilical cord blood samples were isolated within 24 hours from birth and subsequently screened for ETV6-RUNX1 transcripts using a highly sensitive real-time reverse transcription polymerase chain reaction assay. In first-run polymerase chain reaction, 14 samples were positive at levels below 10 ؊5 , of which specific hybridization reflecting the relevant genetic region was positive in 9 cases. Repeated analyses using stored mRNA and flowcytometric sorting of a CD19 ؉ , CD8 ؉ , and CD19 ؊ /CD8 ؊ subpopulations from cryopreserved mononuclear cells from the same cord blood samples (mean sorted: 18 ؋ 10 6 cells) revealed no positive findings, which demonstrates that the level and/or frequency of ETV6-RUNX1-positive cells is markedly lower than suggested in previous studies. IntroductionThe development of childhood B-cell lineage acute lymphoblastic leukemia (ALL) involves (at least) 2 genetic events (hits), 1 the first of which frequently arises prenatally. [2][3][4][5][6][7][8][9][10][11] Unless the postnatal genetic hit(s) is inevitable, the prevalence of newborns harboring preleukemic first hit-cells should exceed the cumulative incidence of the corresponding leukemia. Accordingly, gene transcripts from the most common childhood ALL chromosomal translocation, t(12;21)(p13;q22)[ETV6-RUNX1], were demonstrated in approximately 1% of healthy newborns in one British study, 12 corresponding to 100-fold the cumulative incidence of ETV6-RUNX1-positive ALL in childhood. 13 Noteworthy, the positive cells were reported to occur at levels of 10 Ϫ3 -10 Ϫ4 , and a threshold of 10 Ϫ5 was used for classification of t(12;2)-positive samples with no report of subthreshold frequencies. 12 Since these results are important for mapping the natural history of t(12;21)-positive ALL and furthermore limits the options for future screening, we assessed the prevalence of ETV6-RUNX-positive cells in 1417 newborns. MethodsMononucleated cells (MNCs) were isolated from umbilical cord blood (UCB) samples from healthy, full-term newborns through Ficoll density centrifugation 14 within 24 hours after birth to minimize cellular and/or mRNA degradation. 15 This study was approved by the Danish Data Protection Agency and the Danish Scientific Ethics Committee.mRNA from Ն 2.5 ϫ 10 6 MNCs was extracted using a KingFisher mL robot (ThermoFisher) and the MagAttrackDirect mRNA-M48 Kit (QIAGEN): 750 L of lysis solution, 75 L of magnetic beads, and 550 L of washing solution IϩII. mRNA was eluted in 50 L of RNase-free water, divided into 2 tubes, and stored at Ϫ80°C until use. Surplus MNCs were cryopreserved in liquid nitrogen. For subsequent flow cytometrically sorted subpopulations, mRNA was c...