Insight into congenital absence of the portal vein： Is it rare？

Congenital absence of portal vein （CAPV） was a rare event in the past. However, the number of detected CAPV cases has increased in recent years because of advances in imaging techniques. Patients with CAPV present with portal hypertension （PH） or portosystemic encephalopathy （PSE）, but these conditions rarely occur until the patients grow up or become old. The patients usually visit doctors for the complications of venous shunts, hepatic or cardiac abnormalities detected by ultrasonography （US）, computed tomography （CT） and magnetic resonance imaging （MR1）. The etiology of this disease is not clear, but most investigators consider that it is associated with abnormal embryologic development of the portal vein. Usually, surgical intervention can relieve the symptoms and prevent occurrence of complications in CAPV patients. Moreover, its management should be stressed on a case-by-case basis, depending on the type or anatomy of the disease, as well as the symptoms and clinical conditions of the patient.     

Insight into the mechanism of an iron dioxygenase by resolution of steps following the FeIV═O species

Iron oxygenases generate elusive transient oxygen species to catalyze substrate oxygenation in a wide range of metabolic processes. Here we resolve the reaction sequence and structures of such intermediates for the archetypal non-heme Fe^II and α-ketoglutarate-dependent dioxygenase TauD. Time-resolved Raman spectra of the initial species with ¹⁶O¹⁸O oxygen unequivocally establish the Fe^IV═O structure. ¹H/²H substitution reveals direct interaction between the oxo group and the C1 proton of substrate taurine. Two new transient species were resolved following Fe^IV═O; one is assigned to the ν_FeO mode of an Fe^III─O(H) species, and a second is likely to arise from the vibration of a metal-coordinated oxygenated product, such as Fe^II─O─C₁ or Fe^II─OOCR. These results provide direct insight into the mechanism of substrate oxygenation and suggest an alternative to the hydroxyl radical rebinding paradigm.     

Roles of the CLEC-2–podoplanin interaction in tumor progression

Abstract

Podoplanin is a type-I transmembrane sialomucin-like glycoprotein expressed on the surface of several kinds of tumor cells. The podoplanin receptor is a platelet activation receptor known as C-type lectin-like receptor 2 (CLEC-2), which has been identified as a receptor for the platelet-activating snake venom protein rhodocytin. CLEC-2 is highly expressed in platelets and megakaryocytes and expressed at lower levels in liver Kupffer cells. Podoplanin is expressed in certain types of tumor cells, including squamous cell carcinomas, seminomas, and brain tumors. Podoplanin is also expressed in a wide range of normal cells, including fibroblastic reticular cells in lymph nodes, kidney podocytes, and lymphatic endothelial cells, but not vascular endothelial cells. Metastasis of podoplanin-positive lung tumors injected from the tail vein is greatly inhibited in CLEC-2-depleted mice or in anti-podoplanin antibody-treated mice. These findings suggest that the CLEC-2–podoplanin interaction facilitates hematogenous tumor metastasis. Platelets may increase the survival of tumor cells by covering tumor cells and physically protecting them from shear stress or immune cells in the bloodstream. Alternatively, platelets may stimulate the epithelial–mesenchymal transition of tumor cells to facilitate their extravasation from blood vessels. Cell proliferation is stimulated in podoplanin-expressing tumor cells by the coculture with platelets, but the effects of the CLEC-2–podoplanin interaction on tumor growth in vivo are not yet resolved. It is possible that the CLEC-2–podoplanin interaction facilitates tumor-related thrombosis, subsequent inflammation, inflammation-induced cachexia, and reduced survival. Considering these findings, anti-podoplanin and anti-CLEC-2 drugs are promising therapies for the prevention of tumor metastasis, progression, and tumor-related symptoms, which may result in longer survival in cancer patients. There are advantages and disadvantages of anti-podoplanin vs. anti-CLEC-2 therapy. Side effects in podoplanin-expressing normal tissues due to treatment with anti-podoplanin and temporal thrombocytopenia due to treatment with anti-CLEC2 are potential problems, although solutions to these problems have been reported.     

Tick–tock–tick–tock: the impact of circadian rhythm disorders on cardiovascular health and wellness

Humans spend a third of their lives asleep. A well–balanced synchrony between sleep and wakefulness is needed to maintain a healthy lifestyle. Optimal sleep is based on an individual's inherent sleep requirement and circadian rhythm. If either one or both of these critical elements are disrupted, daytime dysfunction, non–restorative sleep, and/or reduced sense of well-being may result. While the medical community is more familiar with sleep disorders such as sleep apnea, insomnia, and narcolepsy, circadian rhythm sleep wake disorders (CRSWDs) are less known, despite these being common within the general population. CRSWDs are comprised of the following: shiftwork disorder, delayed sleep phase disorder, advanced sleep phase disorder, jet lag disorder, non–24–hour sleep–wake disorder, and irregular sleep–wake rhythm disorder. In general, a CRSWD results when there is misalignment between the sleep pattern and the desired sleep schedule, dictated by work, family, and social schedules. Subsequently, patients have difficulty falling asleep, maintaining sleep, and/or experience poor quality sleep predisposing them to insomnia or excessive sleepiness. In this article, we review the core concepts related to sleep, and sleep deprivation in the context of CRSWDs.     

Do demographic variables affect the timing of referral to the nephrologist?

The consequences of late referrals for nephrological care include: increased morbidity, poorer quality of life on dialysis and probably increased mortality. Few studies look at the socio‐demographic factors which influence referral to the nephrologist. There is good evidence from studies in other areas of health care that socio‐demographic and economic factors influence access to health care. It is important that the nephrology community understand whom the individuals are who likely to be referred late so that we can address any inequality in access to services. We studied all of the patients who started renal replacement therapy in our unit over a five‐year period, 1^st January 1996 to 31^st December 2000 (n = 494). We collected data on gender, age at referral, ethnicity, the date that the individual started dialysis as well as the date they were first seen by a nephrologist. We analysed the data to see if age, gender or ethnicity was associated with timing of referral. If an individual had seen a nephrologist more than three months prior to starting dialysis, they were termed ‘early referred’, if not they were termed ‘late referred’. Since this was a sociologically driven research project, we set statistical significance at the 10% (0.1) level. Our data showed that gender did not affect the timing of referral (p = ns), ethnicity affected referral in so much as whites were more likely to be referred late than blacks (p = 0.08) but no more so than non‐whites (p = ns). People under the age of 30 were statistically more likely to be referred late than people over the age of 30 years (p = 0.027) as were people under the age of 40 (p = 0.047). We interpret these finding as demonstrating that health care professionals are referring older people and people from the black community in good time and that, in contrast to other studies of inequalities in health, these findings demonstrate that the elderly and ethnic minorities are not being disadvantaged.     

Prevention of hospital-associated venous thromboembolism — Insight from the Getting It Right First Time thrombosis survey in England

A national Venous Thromboembolism (VTE) Prevention Programme was introduced in England in 2010, with limited subsequent study of its impact. Whilst the National Outcomes Framework reports VTE deaths related to hospitalisation annually, there are little data regarding VTE prevention practice or non-fatal VTE associated with hospitalisation. We report the first national thrombosis survey undertaken in collaboration with Getting It Right First Time. 98 Trusts (103 sites, 67% of 144 invited) participated in at least one survey, contributing data regarding VTE prevention in 9553 patients. Anti-coagulant thromboprophylaxis was prescribed to 88% (when indicated), with 8.1% of patients missing doses. Written patient information was provided to 31%. Of 4595 episodes of hospital-associated VTE, 13% were considered potentially preventable. The survey highlights the success of the national programme and areas for improvement in delivery of thromboprophylaxis and patient information.     

Targeting diverse protein–protein interaction interfaces with α/β-peptides derived from the Z-domain scaffold

Peptide-based agents derived from well-defined scaffolds offer an alternative to antibodies for selective and high-affinity recognition of large and topologically complex protein surfaces. Here, we describe a strategy for designing oligomers containing both α- and β-amino acid residues (“α/β-peptides”) that mimic several peptides derived from the three-helix bundle “Z-domain” scaffold. We show that α/β-peptides derived from a Z-domain peptide targeting vascular endothelial growth factor (VEGF) can structurally and functionally mimic the binding surface of the parent peptide while exhibiting significantly decreased susceptibility to proteolysis. The tightest VEGF-binding α/β-peptide inhibits the VEGF₁₆₅-induced proliferation of human umbilical vein endothelial cells. We demonstrate the versatility of this strategy by showing how principles underlying VEGF signaling inhibitors can be rapidly extended to produce Z-domain–mimetic α/β-peptides that bind to two other protein partners, IgG and tumor necrosis factor-α. Because well-established selection techniques can identify high-affinity Z-domain derivatives from large DNA-encoded libraries, our findings should enable the design of biostable α/β-peptides that bind tightly and specifically to diverse targets of biomedical interest. Such reagents would be useful for diagnostic and therapeutic applications.Designed molecules that bind selectively to specific sites on proteins may serve as inhibitors of medically important macromolecular interactions or diagnostic tools for biomarker detection. Small molecules often fail for these applications because of the relatively large and irregularly shaped target surfaces (1–3). In contrast, large polypeptides (e.g., antibodies) can frequently be developed to recognize a protein surface with high affinity and selectivity and represent the state of the art for engineering ligands for specific biomacromolecular targets. Large polypeptides, however, suffer several disadvantages for in vivo applications, including costly production, low storage stability, and/or low bioavailability because of rapid proteolytic degradation (4, 5).Backbone-modified peptides, an underexplored class of molecules, are proving to be a fruitful source of tight-binding and specific protein ligands. Peptidic oligomers that contain β-amino acid residues interspersed among α-residues (“α/β-peptides”) can effectively mimic the recognition surface projected by an α-helix and thereby disrupt or augment protein–protein interactions in which one partner contributes a single helix to the interface (6, 7). The unnatural backbone diminishes α/β-peptide susceptibility to proteolytic degradation relative to conventional peptides (α-residues only, “α-peptides”). As a result, α/β-peptides can exhibit improved pharmacokinetic properties in vivo relative to analogous α-peptides (8, 9). To date, however, the α/β-peptide strategy has been restricted to mimicry of isolated α-helices, which is a significant limitation given that most protein–protein interactions are mediated by surfaces that are broader than can be covered by a single, regular helix (1–4, 10).Several small proteins have been explored as scaffolds that can be adapted to interact with structurally diverse protein-binding partners (11–13). The defined tertiary structures of such scaffolds allow them to present large binding surfaces that can engage large and complementary surfaces on target proteins. The “Z-domain” or “affibody” scaffold (14) is a widely studied example that is derived from domain B of staphylococcal protein A (15). The parent Z-domain (Z-IgG) (Fig. 1A) is a 58-residue engineered analog of domain B that retains affinity for the Fc portion of IgG, the natural binding partner of protein A (16). Z-IgG adopts a three-helix bundle tertiary structure, with a large surface (>600 Ų buried in the interface with Fc) formed by helices 1 and 2 contributing most of the Fc-contacting residues. Helix 3 stabilizes the Z-domain fold by packing against the other two helices (15, 17).Open in a separate windowFig. 1.Design of α/β-peptides based on the Z-domain scaffold. (A) Sequences of peptides previously derived from the Z-domain scaffold Z-VEGF, Z-IgG, and Z-TNFα targeting VEGF (19), IgG (16), and TNFα (20), respectively. Helices 1, 2, and 3 are indicated by brackets. For Z-VEGF and Z-TNFα, residues on the protein-binding face of helices 1 and 2 that were identified via randomization and selection (including the unintentionally incorporated Ala¹⁴ in Z-VEGF) are shown in red. For Z-IgG, the parent Z-domain, red positions indicate the corresponding residues that contact IgG. Sequences are arranged based on structural alignment of helical regions. (B) Strategy for the design of α/β-peptide mimics of Z-VEGF (shown in yellow and red). Red residues indicate selected residues that contact VEGF_8–109 (shown in gray) in the cocrystal structure. Sites targeted for nonnatural amino acid substitutions shown in teal. Figure is based on PDB ID code 3S1K.The composite surface displayed by helices 1 and 2 of the Z-domain scaffold can be crafted for specific binding to diverse protein partners because the three-helix bundle tertiary structure tolerates substitutions at solvent-exposed positions (18). Combinatorial randomization of as many as 13 solvent-exposed positions on helices 1 and 2, followed by affinity-based selection, has identified Z-domain derivatives that bind to a variety of targets (12, 14), including vascular endothelial growth factor (VEGF) (peptide Z-VEGF; Fig. 1 A and B) (19), tumor necrosis factor-α (TNFα) (peptide Z-TNFα; Fig. 1A) (20), and human epidermal growth factor receptor 2 (HER2) (21). Such Z-domain analogs might represent alternatives to antibodies for selective detection of disease marker proteins or for blocking deleterious signal transduction (11–14). In many cases, selection from a phage library has identified Z-domain derivatives that exhibit dissociation constants (K_D) in the nanomolar range for a chosen protein target. Affinity maturation can enhance binding to K_D values in the picomolar range (21). Recent clinical evaluations of radiolabeled Z-domain derivatives targeting HER2 revealed that these peptides could be safely used to image HER2-overexpressing lesions in breast cancer patients (22), a result that highlights the medical promise of the Z-domain scaffold.The high α-helix content of the Z-domain scaffold led us to envision that α/β-peptide analogs could be developed as binding partners for target proteins (23). We hypothesized that α→β replacements focused at sites distinct from the positions within helices 1 and 2 that mediate target recognition could reduce susceptibility to proteolytic degradation while maintaining high affinity for the partner. This design hypothesis is encouraged by two reports of Z-domain derivatives lacking helix 3 that retained affinity for their designated targets (24–26). Here, we describe the development of α/β-peptides that structurally and functionally mimic Z-VEGF. We demonstrate the versatility of this α/β-peptide strategy by showing how principles revealed in the VEGF-based effort can be extended to achieve functional mimicry of Z-domain peptides (Z-IgG and Z-TNFα) that bind to two other protein partners, IgG and TNFα.     

Titin strain contributes to the Frank–Starling law of the heart by structural rearrangements of both thin- and thick-filament proteins

The Frank–Starling mechanism of the heart is due, in part, to modulation of myofilament Ca²⁺ sensitivity by sarcomere length (SL) [length-dependent activation (LDA)]. The molecular mechanism(s) that underlie LDA are unknown. Recent evidence has implicated the giant protein titin in this cellular process, possibly by positioning the myosin head closer to actin. To clarify the role of titin strain in LDA, we isolated myocardium from either WT or homozygous mutant (HM) rats that express a giant splice isoform of titin, and subjected the muscles to stretch from 2.0 to 2.4 μm of SL. Upon stretch, HM compared with WT muscles displayed reduced passive force, twitch force, and myofilament LDA. Time-resolved small-angle X-ray diffraction measurements of WT twitching muscles during diastole revealed stretch-induced increases in the intensity of myosin (M2 and M6) and troponin (Tn3) reflections, as well as a reduction in cross-bridge radial spacing. Independent fluorescent probe analyses in relaxed permeabilized myocytes corroborated these findings. X-ray electron density reconstruction revealed increased mass/ordering in both thick and thin filaments. The SL-dependent changes in structure observed in WT myocardium were absent in HM myocardium. Overall, our results reveal a correlation between titin strain and the Frank–Starling mechanism. The molecular basis underlying this phenomenon appears not to involve interfilament spacing or movement of myosin toward actin but, rather, sarcomere stretch-induced simultaneous structural rearrangements within both thin and thick filaments that correlate with titin strain and myofilament LDA.The Frank–Starling law of the heart describes a cardiac regulatory control mechanism that operates on a beat-to-beat basis (1). There is a unique relationship between ventricular end-systolic volume and end-systolic pressure that is determined by cardiac contractility. As a result, ventricular stroke volume is directly proportional to the extent of diastolic filling. In conjunction with heart rate and contractility, the Frank–Starling mechanism constitutes a major determinant of cardiac output. Although the Frank–Starling mechanism has been well established for well over a century, the molecular mechanisms underlying this phenomenon are not resolved (1). At the cellular level, an increase in sarcomere length (SL) results in an immediate increase in twitch force development. Existing data, mostly derived from permeabilized isolated myocardium, strongly support the notion that this phenomenon is due to an increase in the Ca²⁺ responsiveness of the cardiac contractile apparatus, a phenomenon termed “myofilament length-dependent activation” (LDA) (1).The mechanism by which the mechanical strain signal is transduced by the cardiac sarcomere is not known. We have recently demonstrated that LDA develops within a few milliseconds following a change in SL (2), a finding suggestive of a molecular mechanism caused by strain-dependent mechanical rearrangement of contractile proteins. Moreover, although LDA is a general property of striated muscle, it manifests itself to a much greater extent in cardiac muscle compared with slow-twitch skeletal muscle (3). Cardiac LDA has been shown to be modulated by contractile protein phosphorylation (4–7), as well as by cardiac disease-associated mutations within various contractile proteins (6). In addition, evidence has emerged that the passive force originating from the giant elastic sarcomeric protein titin directly acts to modulate myofilament Ca²⁺ responsiveness (8, 9). Of note, the titin molecule spans the entire half-sarcomere from the Z-disk to the center of the thick filament, and is thus well positioned within the contractile apparatus to relay the mechanical SL input signal (8). The mechanisms underlying the impact of titin strain on myofilament LDA, however, are incompletely understood.A unifying theory has been advanced whereby the distance between the thin and thick filaments constituting the muscle’s sarcomeres is proposed to modulate myofilament Ca²⁺ responsiveness by affecting the probability of cross-bridge formation. Consistent with this notion, analyses of X-ray diffraction patterns obtained from both isolated cardiac and skeletal muscle reveal an inverse relationship between myofilament lattice spacing and SL (10). However, in a multitude of experimental models, we could not find a consistent correlation between myofilament lattice spacing and myofilament Ca²⁺ responsiveness, rendering interfilament spacing a less likely candidate for the molecular mechanism underlying LDA (1). Instead, we obtained experimental evidence suggesting a direct impact of SL on the spread of cooperative activation along the thin filament (11), potentially by modulation of the ordering of myosin heads in relaxed muscle, that is, before electrical activation (12). However, the primary molecular mechanism by which the strain signal is transmitted to the contractile apparatus could not be determined by those studies.Here, we use a rat model in which a naturally occurring mutation within the splicing factor RBM20 disrupts titin mRNA splicing. One result of this mutation is the cardiac expression of a giant titin isoform in homozygous mutant (HM) animals at all ages (13). The presence of the giant titin isoform in HM myocardium was associated with reduced cardiac passive force upon stretch, as well as a blunted Frank–Starling response and reduced myofilament LDA. Time-resolved small-angle X-ray diffraction revealed stretch-induced conformational structural changes in both thin- and thick-filament contractile proteins during diastole in WT, but not HM, muscles. Our results suggest a prominent contribution of titin strain to the cardiac Frank–Starling mechanism. The mechanism underlying this phenomenon appears not to involve interfilament spacing or movement of myosin heads toward actin in the relaxed muscle but, rather, stretch-induced structural rearrangements in both the thin and thick filaments that is likely directly mediated by titin strain.     

Subclinical infections of cardiac implantable electronic devices: Insights into the host–bacteria dialog from blood and pocket tissue with pyrosequencing

While bacteria exist in CIED patients without clinical signs of infection, the underlying bacterial community structure and diversity in the bloodstream and pocket tissue of asymptomatic CIED patients remain unknown. In this study, we performed high-throughput 454 pyrosequencing of bacterial 16S rDNA of blood and pocket tissue from 54 asymptomatic CIED patients as well as blood from 30 normal individuals (normal controls). Firstly, we observed a significant increase of blood bacterial diversity in patients as compared with blood of normal subjects or patient tissues. We also found significant differences in 13 blood-associated bacterial genera between patients and normal subjects, and 14 bacteria genera between blood and tissues within patients. Secondly, we found that the serum levels of four inflammatory markers (CRP, IL-1β, IL-6, and MCP-1) in CIED patients were significantly higher than those in normal subjects. Thirdly, we found that there were significant correlations between 43 bacterial species and these inflammatory markers. Taken together, our results reveal a high diversity in the microbial community in CIED patients, and suggest the potential roles of multiple bacteria co-occurrence in the CIED subclinical infections.     

What is the evidence status of Appropriate Use Criteria (AUC)? Insight from a matching exercise with the guidelines for echocardiography

There is interest in adapting the American Appropriate Use Criteria (AUC) for transthoracic echocardiography to Australian practice. We matched 90 of 98 AUC with the guidelines (53 appropriate, 12 sometimes appropriate, 25 rarely appropriate), but eight lacked any match. Among the matched criteria, 76 (82%) indications were concordant with the guidelines. A stronger evidence base would be desirable to settle these discrepancies before Australian adoption of AUC.     

Causes of death in HIV-infected patients from the Cologne–Bonn cohort

Purpose

Causes of death in human immunodeficiency virus (HIV)-infected subjects have changed in countries with high resources over the last several years. Acquired immunodeficiency syndrome (AIDS)-related diseases have become less prevalent, whereas deaths due to non-AIDS causes are increasing. The aim of the present study was to analyse causes of death in the Cologne–Bonn cohort.

Methods

Causes of death from the Cologne–Bonn cohort between 2004 and 2010 were systematically recorded using the CoDe algorithm (The Coding Causes of Death in HIV Project).

Results

In 3,165 patients followed from 2004 to 2010, 182 deaths occurred (5.7 %, 153 males, 29 females). The median age at the time of death was 47 years (range 24–85 years). The most frequent causes of death were AIDS-defining events (n = 60, 33 %), with non-Hodgkin lymphoma (NHL) (n = 29, 16 %) and infections (n = 20, 11 %) being the leading entities in this category. Non-AIDS malignancies accounted for 16 % (n = 29), non-HIV-related infections for 10 % (n = 18), cardiovascular diseases for 7 % (n = 14), suicide or accident for 4 % (n = 7) and liver diseases for 3 % (n = 5) of deaths (unknown n = 47, 26 %). Although the majority of patients (92.5 %) was on antiretroviral therapy (ART), only 50 % were virologically suppressed (HIV-RNA <50 copies/mL) and 44 % had a decreased CD4+ count (<200/μL) at their last visit before death.

Conclusion

One-third of the causes of death in our cohort between 2004 and 2010 was AIDS-related. Since most of these deaths occur with severe immune suppression, they can possibly be prevented by the early diagnosis and treatment of HIV infection. Care providers must be aware of an increased risk for a broad range of diseases in HIV-infected patients and should apply appropriate preventive measures.     

Synergistic interaction of hypertension and diabetes on chronic kidney disease: Insights from the National Health and Nutrition Examination Survey 1999–2006

BackgroundHypertension and diabetes mellitus are 2 major risk factors for chronic kidney disease (CKD). However, whether hypertension and diabetes have a synergistic interaction towards greater renal damage remains unclear. Our study aimed to investigate whether hypertension and diabetes act synergistically towards CKD.Methods13,693 subjects from the cross-sectional National Health and Nutritional Examination Survey 1999–2006 were included in our analyses. The associations were investigated by multivariate logistic regression models. The interaction was evaluated on both additive and multiplicative scale.ResultsThe prevalence of CKD was 17.62%. After adjustment, subjects with both hypertension and diabetes had a 4.710 (3.652–6.073) times risk of CKD than non-hypertensive non-diabetic subjects, higher than that of subjects with only hypertension or diabetes (1.732, 95% CI: 1.502–1.997 and 2.407, 95% CI: 1.815–3.194, respectively). Furthermore, significant interaction was observed between hypertension and diabetes towards CKD in the additive scale (relative excess risk due to interaction: 1.570, 95% CI: 0.507–2.633; the attributable proportion due to interaction: 0.333, 95% CI: 0.168–0.499; Synergy index: 1.734, 95% CI: 1.239–2.426). Additionally, analyses of the associations with components of the primary endpoint demonstrated that the interaction was also applicable to those with reduced eGFR, albuminuria or normoalbuminuric CKD.ConclusionsThe joint effect of hypertension and diabetes was significantly larger than the sum of their independent impact on CKD. Our findings may provide intuitionistic and straightforward illustrations for the public to understand the danger of combined hypertension and diabetes on the renal injury.     

Is timing of the first antenatal visit associated with adverse birth outcomes? Analysis from a population-based birth cohort

BackgroundAdequate antenatal care can improve maternal and child health outcomes. The UK National Institute for Health and Care Excellence (NICE) recommends that the first antenatal visit with a health-care professional should occur by 10 weeks' gestation. The WHO Focused Antenatal Care Protocol recommends that it happens no later than 16 weeks' gestation. We aimed to examine the associations between timing of the first antenatal booking visit and adverse birth outcomes including low birthweight, preterm birth, and stillbirth.MethodsAntenatal and delivery records from a population-based cohort consisting of all women receiving maternity care at University Hospital Southampton, UK, during 2000–13 were analysed (74 449 pregnancies of which 64 739 had delivery data). We conducted multiple logistic modelling to assess the associations of interest. All models computed a cluster-robust standard error of the difference to account for clustering in women with more than one pregnancy included.Findings74 220 pregnancies had booking timing information. Mean gestational age at booking was 12·6 weeks (SD 5·3), with 21 482 pregnancies (29%) having their booking visit by 10 weeks' gestation, 45 015 (61%) by 12 weeks', 59 986 (81%) by 14 weeks', and 65 755 (89%) by 16 weeks'. Of the 64 246 livebirths, 4009 (6·2%) were of low birthweight (<2500 g) and 4253 (6·6%) were preterm (<37 weeks'). There were 302 (0·5%) stillbirths. Pregnancies with a booking visit after 16 weeks' were more likely to lead to low birthweight (odds ratio 1·2, 95% CI 1·04–1·4; p=0·01, adjusted for maternal age, body-mass index, blood pressure, parity, ethnicity, employment status, educational attainment, alcohol consumption, smoking, infertility treatment, baby's sex, and gestational age). Booking after 14 weeks' was associated with preterm birth (1·3, 1·2–1·4; p<0·0001, adjusted for all except gestational age). With the NICE cut-off of 10 weeks', no significant associations were seen with low birthweight (adjusted odds ratio 1·1, 95% CI 1·0–1·2), preterm birth (1·0, 0·9–1·1), or stillbirth (1·1, 0·8–1·5).InterpretationDelayed first antenatal visit (one in 10 women after 16 weeks' and one in five women after 14 weeks' gestation) was associated with adverse birth outcomes. However, this association could represent residual confounding. A Cochrane review found no effect of reduced versus standard number of antenatal visits on preterm birth and low birthweight, although all included trials recruited women after booking. Emphasis on early booking in primary care is recommended.FundingNone.