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A growing body of studies supports the existence of Townsend’s wall-attached eddies in wall turbulence under the condition of sufficiently high Reynolds numbers. In the present work, we uncover the signature of Townsend’s wall-attached eddies in low-Reynolds-number wall turbulence. To this end, we use a three-dimensional clustering methodology to identify the wall-attached structures of intense streamwise and spanwise velocity fluctuations in turbulent channel flows at four Reynolds numbers (
, 358, 547 and 934). The statistical properties of the structures, such as their geometric self-similarity, population density and statistical moments, are investigated and compared with the predictions of the attached-eddy model. Particular attention is paid to the asymmetries between high- and low-speed wall-attached streaky structures, and we show that the former are a closer representation of the wall-attached eddies. This observation is ascribed to the differences between the sweep and ejection events associated with the streaks. We also examine the Reynolds-number effects on the statistical properties of the structures, and find that the signature of attached eddies can be observed within the Reynolds-number range under scrutiny. Our approach paves the way to cost-efficient model development and flow prediction using computationally more affordable simulations at low Reynolds numbers.
B vitamins (including folate, vitamin B2, vitamin B6 and vitamin B12) and methionine are essential for methylation reactions, nucleotide synthesis, DNA stability and DNA repair. However, epidemiological evidence among Chinese population is limited. The objective of this study was to evaluate B vitamins and methionine in relation to colorectal cancer risk in a Chinese population. A case-control study was conducted from July 2010 to April 2019. A total of 2502 patients with colorectal cancer were recruited along with 2538 age (5-year interval) and sex matched controls. Dietary data was collected by using a validated food frequency questionnaire. Multivariable logistic regression was used to assess odds ratios (ORs) and 95% confidence interval (CI). The intake of folate, vitamin B2, vitamin B6 and vitamin B12 was inversely associated with colorectal cancer risk. The multivariable ORs for the highest quartile versus the lowest quartile were 0.62 (95%CI 0.51, 0.74; Ptrend < 0.001) for folate, 0.46 (95%CI 0.38, 0.55; Ptrend < 0.001) for vitamin B2, 0.55 (95%CI 0.46, 0.76; Ptrend < 0.001) for vitamin B6 and 0.72 (95%CI 0.60, 0.86; Ptrend < 0.001) for vitamin B12, respectively. No statistically significant association was found between methionine intake and colorectal cancer risk. Stratified analysis by sex showed that the inverse associations between vitamin B12 and methionine intake and colorectal cancer risk were found only among women. This study indicated that higher intake of folate, vitamin B2, vitamin B6 and vitamin B12 was associated with decreased risk of colorectal cancer in Chinese population.
Few studies investigated the association between maternal dietary patterns (DPs) during pregnancy, derived from reduced-rank regression (RRR), and fetal growth. This study aims to identify DPs during pregnancy associated with macro- and micronutrient intakes, using the RRR method, and to examine their relationship with birth weight (BW). We used data of 7194 women from a large-scale cross-sectional survey in Northwest China. Dietary protein, carbohydrate, heme iron density, and the ratio of poly- and monounsaturated fatty acids to saturated fatty acids were used as the intermediate variables in the RRR model to extract DPs. Generalized estimating equation models were applied to evaluate the associations between DPs and BW and related outcomes (including BW z-score, low birth weight [LBW], and small-for-gestational-age [SGA]). Four DPs during pregnancy were identified. Socio-demographically disadvantaged pregnant women were more likely to have lower BW and lower adherence to DP1 (high legumes, soybean products, vegetables, and animal source foods, with relative low wheat and oils). Women with medium and high adherence to DP1 had significantly increased BW (medium: 28.6 [7.1, 50.1]; high: 25.2 [2.7, 47.6]) and BW z-score, and had significantly reduced risks of LBW and SGA. The associations were stronger among women with babies <3100 g. There is no association between other DPs and outcomes. Higher adherence to the DP that was high in legumes, soybean products, vegetables, and animal source foods was associated with improved BW in the Chinese pregnant women, particularly among those with disadvantageous socio-demographic conditions.
This study presents monazite and rutile U–Pb and hornblende and biotite 40Ar/39Ar geochronological data for high-grade rocks of the eastern Grenville-aged Rayner orogen at Mount Brown in order to analyse the extent and degree of Pan-African-aged reworking. Monazite from paragneiss yields U–Pb ages of 910 Ma for larger granular grains and 670–630 Ma for smaller globular beads around garnet porphyroblasts or hosted by symplectites. Rutile from leucogneiss yields U–Pb ages of 520–515 Ma. Hornblende and biotite from different rock types yield 40Ar/39Ar plateau ages of 744 and 520–505 Ma, respectively. Combining these results with published zircon U–Pb age data suggests that granulite facies metamorphism occurred at 910 Ma, with a local low-temperature fluid flow event at 670–630 Ma and thermal reworking at 520–505 Ma. The older age of 744 Ma may reflect cooling or partial resetting of the hornblende 40Ar/39Ar system, indicating that Pan-African-aged reworking did not exceed temperatures much higher than the hornblende Ar closure temperature. These data also suggest that the complete isotopic resetting of some minerals may occur without the growth of new mineral phases, providing an example of the style of reworking that is likely to occur in polymetamorphic terranes.
The surface energy budget over the Antarctic sea ice from 8 April 2016 through 26 November 2016 are presented. From April to October, Sensible heat flux (SH) and subsurface conductive heat flux (G) were the heat source of surface while latent heat flux (LE) and net radiation flux (Rn) were the heat sink of surface. Our results showed larger downward SH (due to the warmer air in our site) and upward LE (due to the drier air and higher wind speed in our site) compared with SHEBA data. However, the values of SH in N-ICE2015 campaign, which located at a zone with stronger winds and more advection of heat in the Arctic, were comparable to our results under clear skies. The values of aerodynamic roughness length (z0m) and scalar roughness length for temperature (z0h), being 1.9 × 10−3 m and 3.7 × 10−5 m, were suggested in this study. It is found that snow melting might increase z0m. Our results also indicate that the value of log(z0h/z0m) was related to the stability of stratification. In addition, several representative parameterization schemes for z0h have been tested and a couple of schemes were found to make a better performance.
Whether the first-degree relatives (FDRs) of patients with obsessive-compulsive disorder (OCD) have an increased risk of the major psychiatric disorders, namely schizophrenia, bipolar disorder, OCD, major depressive disorder (MDD), autism spectrum disorder (ASD), and attention deficit hyperactivity disorder (ADHD), remains unclear.
Using the Taiwan National Health Insurance Research Database with the whole population sample size (n = 23 258 175), 89 500 FDRs, including parents, offspring, siblings, and twins, of patients with OCD were identified in our study. The relative risks (RRs) of major psychiatric disorders were assessed among FDRs of patients with OCD.
FDRs of patients with OCD had higher RRs of major psychiatric disorders, namely OCD (RR 8.11, 95% confidence interval (CI) 7.68–8.57), bipolar disorder (RR 2.85, 95% CI 2.68–3.04), MDD (RR 2.67, 95% CI 2.58–2.76), ASD (RR 2.38, 95% CI 2.10–2.71), ADHD (RR 2.19, 95% CI 2.07–2.32), and schizophrenia (RR 1.97, 95% CI 1.86–2.09), compared with the total population. Different familial kinships of FDRs, such as parents, offspring, siblings, and twins consistently had increased risks for these disorders. In addition, a dose-dependent relationship was found between the numbers of OCD probands and the risk of each major psychiatric disorder.
The FDRs, including parents, offspring, siblings, and twins, of patients with OCD have a higher risk of OCD, schizophrenia, bipolar disorder, MDD, ADHD, and ASD. The familial co-aggregation of OCD with OCD and other major psychiatric disorders was existent in a dose-dependent manner. Given the increased risks of psychiatric disorders, medical practitioners should closely monitor the mental health of the FDRs of patients with OCD.
A culture- and age-appropriate instrument for measuring emotion regulation ability is needed for the research and practice of Chinese adolescents’ emotion regulation. This study developed and validated a situational judgment test of emotion regulation ability for Chinese youth (STER-CY). Three samples were recruited, and approximately 4380 5th- to 11th-grade students (but no 9th-grade students) participated in the study. Researchers collected emotional situations and responses based on the life of indigenous samples and examined the reliability and validity of the test scores. The results showed that Cronbach’s alpha and test–retest correlations provided evidence for the reliability of the test scores. Exploratory and confirmatory factor analysis supported unidimensionality. Construct validity was further verified by convergent and discriminant validity. Criteria-related validity was confirmed by the correlations between this test and some outcome variables related to emotion regulation. It was also found that girls scored higher on this test than boys did and that emotion regulation ability significantly increased from 5th to 7th grade, but it did not improve from 7th to 11th grade. Considered together, these findings showed that the STER-CY is a psychometrically sound measure of emotion regulation ability and can be used in future research and practice.
To evaluate the effects of gestational weight gain (GWG) in the first trimester (GWG-F) and the rate of gestational weight gain in the second trimester (RGWG-S) on gestational diabetes mellitus (GDM), exploring the optimal GWG ranges for the avoidance of GDM in Chinese women.
A population-based prospective study was conducted. Gestational weight was measured regularly in every antenatal visit and assessed by the Institute of Medicine (IOM) criteria (2009). GDM was assessed with the 75-g, 2-h oral glucose tolerance test at 24–28 weeks of gestation. Multivariable logistic regression was performed to assess the effects of GWG-F and RGWG-S on GDM, stratified by pre-pregnancy BMI. In each BMI category, the GWG values corresponding to the lowest prevalence of GDM were defined as the optimal GWG range.
Pregnant women (n 1910) in 2017.
After adjusting for confounders, GWG-F above IOM recommendations increased the risk of GDM (OR; 95 % CI) among underweight (2·500; 1·106, 5·655), normal-weight (1·396; 1·023, 1·906) and overweight/obese women (3·017; 1·118, 8·138) compared with women within IOM recommendations. No significant difference was observed between RGWG-S and GDM (P > 0·05) after adjusting for GWG-F based on the previous model. The optimal GWG-F ranges for the avoidance of GDM were 0·8–1·2, 0·8–1·2 and 0·35–0·70 kg for underweight, normal-weight and overweight/obese women, respectively.
Excessive GWG in the first trimester, rather than the second trimester, is associated with increased risk of GDM regardless of pre-pregnancy BMI. Obstetricians should provide more pre-emptive guidance in achieving adequate GWG-F.
We aimed to comprehensively examine the association of breast-feeding, types and initial timing of complementary foods with adolescent cognitive development in low- and middle-income countries. We conducted a prospective cohort study of 745 adolescents aged 10–12 years who were born to women who participated in a randomised trial of prenatal micronutrient supplementation in rural Western China. An infant feeding index was constructed based on the current WHO recommendations. Full-scale intelligence quotient (FSIQ) was assessed and derived by the fourth edition of the Wechsler Intelligence Scale for Children. The duration of exclusive or any breast-feeding was not significantly associated with adolescent cognitive development. Participants who regularly consumed Fe-rich or Fe-fortified foods during 6–23 months of age had higher FSIQ than those who did not (adjusted mean differences 4·25; 95 % CI 1·99, 6·51). For cows’/goats’ milk and high protein-based food, the highest FSIQ was found in participants who initially consumed at 10–12 and 7–9 months, respectively. A strong dose–response relationship of the composite infant feeding index was also identified, with participants in the highest tertile of overall feeding quality having 3·03 (95 % CI 1·37, 4·70) points higher FSIQ than those in the lowest tertile. These findings suggest that appropriate infant feeding practices (breast-feeding plus timely introduction of appropriate complementary foods) were associated with significantly improved early adolescent cognitive development scores in rural China. In addition, improvement in Fe-rich or Fe-fortified foods complementary feeding may produce better adolescent cognitive development outcomes.
The effects of dietary vitamin D, Ca and dairy products intakes on colorectal cancer risk remain controversial. The present study investigated the association between these dietary intakes and the risk of colorectal cancer in Guangdong, China. From July 2010 to December 2018, 2380 patients with colorectal cancer and 2389 sex- and age-matched controls were recruited. Dietary intake data were collected through face-to-face interviews using a validated FFQ. Unconditional multivariable logistic regression models were used to calculate the OR and 95 % CI after adjusting for various confounders. Higher dietary vitamin D and Ca intakes were associated with 43 and 52 % reductions in colorectal cancer risk, with OR of 0·57 (95 % CI 0·46, 0·70) and 0·48 (95 % CI 0·39, 0·61), respectively, for the highest quartile (v. the lowest quartile) intakes. A statistically significant inverse association was observed between total dairy product intake and colorectal cancer risk, with an adjusted OR of 0·32 (95 % CI 0·27, 0·39) for the highest v. the lowest tertile. Subjects who drank milk had a 48 % lower risk of colorectal cancer than those who did not (OR 0·52, 95 % CI 0·45, 0·59). The inverse associations of dietary vitamin D, Ca, total dairy products and milk intakes with the risk of colorectal cancer were independent of sex and cancer site. Our study supports the protective effects of high dietary vitamin D, Ca and dairy products intakes against colorectal cancer in a Chinese population.
Synaptotagmin 1 (Syt1) is an abundant and important presynaptic vesicle protein that binds Ca2+ for the regulation of synaptic vesicle exocytosis. Our previous study reported its localization and function on spindle assembly in mouse oocyte meiotic maturation. The present study was designed to investigate the function of Syt1 during mouse oocyte activation and subsequent cortical granule exocytosis (CGE) using confocal microscopy, morpholinol-based knockdown and time-lapse live cell imaging. By employing live cell imaging, we first studied the dynamic process of CGE and calculated the time interval between [Ca2+]i rise and CGE after oocyte activation. We further showed that Syt1 was co-localized to cortical granules (CGs) at the oocyte cortex. After oocyte activation with SrCl2, the Syt1 distribution pattern was altered significantly, similar to the changes seen for the CGs. Knockdown of Syt1 inhibited [Ca2+]i oscillations, disrupted the F-actin distribution pattern and delayed the time of cortical reaction. In summary, as a synaptic vesicle protein and calcium sensor for exocytosis, Syt1 acts as an essential regulator in mouse oocyte activation events including the generation of Ca2+ signals and CGE.
Rational construction of Z-scheme photocatalysts and exploration of the Z-scheme charge transfer mechanism have drawn much attention in the field of CO2 reduction because of its great potential to alleviate energy crisis and environmental problems. In this study, a series of Z-scheme CdS/BiOI composites were constructed by depositing CdS nanoparticles on the surface of BiOI nanosheets. The synthesized materials were characterized comprehensively, and their photoreduction CO2 activities were evaluated. The results show that the composites exhibit higher photoreduction CO2 activity under visible light irradiation (λ > 400 nm) than pure CdS and BiOI. The yields of CO and CH4 for the optimal composite after 3 h irradiation are 3.32 and 0.54 μmol/g, respectively. The improved photocatalytic activity is attributed to Z-scheme transfer mode of the photogenerated charges in the composites. The mechanism of CO2 reduction is proposed and verified experimentally.
Multiple sulphur isotope compositions of sedimentary pyrites across the Ediacaran–Cambrian (Ed–C) transition and into the early Cambrian from the Xiaotan section, Yunnan, South China, are presented to explore the evolution of the sulphur cycle. The values of δ34Spy range from 13.5 ‰ to 35.8 ‰, and the values of Δ33Spy range from −0.044 ‰ to 0.063 ‰. The first-order observation of highly positive δ34Spy is consistent with sulphur isotope records from other sedimentary successions (with various degrees of enrichment in 34S), reflecting a common feature in cycling of sulphur among ocean basins. The positive values suggest that pyrite was formed in a depositional setting with limiting availability of sulphate that suppressed the expression of microbial fractionations. The first-order observation of a 10-million-year period of negative Δ33Spy beginning around the Ed–C boundary likely reflects changes in isotopic compositions of sulphur influx to the oceans. Such changes are suggested to be linked to a pulse of preferred weathering of sulphides (with negative Δ33S) relative to sulphate, which may reflect enhanced exposure of pyrites in continental margins due to reorganization of continents at this time. Both δ34Spy and Δ33Spy data imply low seawater sulphate levels, and possibly heterogeneity in sulphate concentrations in the world’s coastal oceans. The predictions about sulphur isotope signatures of evolved seawater (with highly positive δ34S and negative Δ33S) at the Xiaotan section are testable with future measurements of carbonate-associated sulphate (CAS), a proxy of ancient oceanic sulphate that carries information about the operation of sulphur cycling on a global scale.
In this study, the thermal deformation of a machine tool structure due to the heat generated during operation was analyzed, and embedded cooling channels were applied to exchange the heat generated during the operation to achieve thermal error suppression. Then, the finite volume method was used to simulate the effect of cooling oil temperature on thermal deformation, and the effect of thermal suppression was experimentally studied using a feed system combined with a cooler to improve the positioning accuracy of the machine tool. In this study, the supply oil temperature in the structural cooling channels was found to significantly affect the position accuracy of the moving table and moving carrier. If the supply oil temperature in the cooling channels is consistent with the operational ambient temperature, the position accuracy of the moving table in the Y direction and the moving carrier in the X and Z directions has the best performance under different feed rates. From the thermal suppression experiments of the embedded cooling channels, the positioning accuracy of the feed system can be improved by approximately 25.5 % during the dynamic feeding process. Furthermore, when the hydrostatic guideway is cooled and dynamic feeding is conducted, positioning accuracy can be improved by up to 47.8 %. The machining accuracy can be improved by approximately 60 % on average by using the embedded cooling channels in this study. Therefore, thermal suppression by the cooling channels in this study can not only effectively improve the positioning accuracy but also enhance machining accuracy, proving that the method is effective for enhancing machine tool accuracy.
Maternal supraphysiological estradiol (E2) environment during pregnancy leads to adverse perinatal outcomes. However, the influence of oocyte exposure to high E2 levels on perinatal outcomes remains unknown. Thus, a retrospective cohort study was conducted to explore the effect of high E2 level induced by controlled ovarian stimulation (COH) on further outcomes after frozen embryo transfer (FET). The study included all FET cycles (n = 10,581) between 2014 and 2017. All cycles were categorized into three groups according to the E2 level on the day of the human Chorionic Gonadotropin trigger. Odds ratios (ORs) and their confidence intervals (CIs) were calculated to evaluate the association between E2 level during COH and pregnancy outcomes and subsequent neonatal outcomes. From our findings, higher E2 level was associated with lower percentage of chemical pregnancy, clinical pregnancy, ongoing pregnancy, and live birth as well as increased frequency of early miscarriage. Preterm births were more common among singletons in women with higher E2 level during COH (aOR1 = 1.93, 95% CI: 1.22–3.06; aOR2 = 2.05, 95% CI: 1.33–3.06). Incidence of small for gestational age (SGA) was more common in both singletons (aOR1 = 2.01, 95% CI: 1.30–3.11; aOR2 = 2.51, 95% CI: 1.69–3.74) and multiples (aOR1 = 1.58, 95% CI: 1.03–2.45; aOR2 = 1.99, 95% CI: 1.05–3.84) among women with relatively higher E2 level. No association was found between high E2 level during COH and the percentage of macrosomia or large for gestational age. In summary, oocyte exposure to high E2 level during COH should be brought to our attention, since the pregnancy rate decreasing and the risk of preterm birth and SGA increasing following FET.
Malnutrition and acute kidney injury (AKI) are common complications in hospitalised patients, and both increase mortality; however, the relationship between them is unknown. This is a retrospective propensity score matching study enrolling 46 549 inpatients, aimed to investigate the association between Nutritional Risk Screening 2002 (NRS-2002) and AKI and to assess the ability of NRS-2002 and AKI in predicting prognosis. In total, 37 190 (80 %) and 9359 (20 %) patients had NRS-2002 scores <3 and ≥3, respectively. Patients with NRS-2002 scores ≥3 had longer lengths of stay (12·6 (sd 7·8) v. 10·4 (sd 6·2) d, P < 0·05), higher mortality rates (9·6 v. 2·5 %, P < 0·05) and higher incidence of AKI (28 v. 16 %, P < 0·05) than patients with normal nutritional status. The NRS-2002 showed a strong association with AKI, that is, the risk of AKI changed in parallel with the score of the NRS-2002. In short- and long-term survival, patients with a lower NRS-2002 score or who did not have AKI achieved a significantly lower risk of mortality than those with a high NRS-2002 score or AKI. Univariate Cox regression analyses indicated that both the NRS-2002 and AKI were strongly related to long-term survival (AUC 0·79 and 0·71) and that the combination of the two showed better accuracy (AUC 0·80) than the individual variables. In conclusion, malnutrition can increase the risk of AKI and both AKI and malnutrition can worsen the prognosis that the undernourished patients who develop AKI yield far worse prognosis than patients with normal nutritional status.
The present study was conducted to evaluate the effects of glucose, soya oil or glutamine on jejunal morphology, protein metabolism and protein expression of the mammalian target of rapamycin complex 1 (mTORC1) signalling pathway in jejunal villus or crypt compartment of piglets. Forty-two 21 d-weaned piglets were randomly allotted to one of the three isoenergetic diets formulated with glucose, soya oil or glutamine for 28 d. On day 14 or 28, the proteins in crypt enterocytes were analysed with isobaric tags for relative and absolute quantification and proteins involved in mTORC1 signalling pathway in villus or crypt compartment cells were determined by Western blotting. Our results showed no significant differences (P > 0·05) in jejunal morphology among the three treatments on day 14 or 28. The differentially expressed proteins mainly took part in a few network pathways, including antimicrobial or inflammatory response, cell death and survival, digestive system development and function and carbohydrate metabolism. On day 14 or 28, there were higher protein expression of eukaryotic initiation factor-4E binding protein-1 in jejunal crypt compartment of piglets supplemented with glucose or glutamine compared with soya oil. On day 28, higher protein expression of phosphor-mTOR in crypt compartment was observed in piglets supplemented with glucose compared with the soya oil. In conclusion, the isoenergetic glucose, soya oil or glutamine did not affect the jejunal morphology of piglets; however, they had different effects on the protein metabolism in crypt compartment. Compared with soya oil, glucose or glutamine may be better energy supplies for enterocytes in jejunal crypt compartment.
Previous studies have shown that the Dietary Approaches to Stop Hypertension (DASH) diet might contribute to managing risk factors of non-alcoholic fatty liver disease (NAFLD), but evidence is limited. We examined the association of DASH diet score (DASH-DS) with NAFLD, as well as the intermediary effects of serum retinol-binding protein-4 (RBP4), serum high-sensitivity C-reactive protein (hs-CRP), serum TAG, homeostasis model assessment of insulin resistance (HOMA-IR) and BMI.
We performed a cross-sectional analysis of a population-based cohort study. Dietary data and lifestyle factors were assessed by face-to-face interviews and the DASH-DS was then calculated. We assessed serum RBP4, hs-CRP and TAG and calculated HOMA-IR. The presence and degree of NAFLD were determined by abdominal sonography.
Guangzhou Nutrition and Health Study participants, aged 40–75 years at baseline (n 3051).
After adjusting for potential covariates, we found an inverse association between DASH-DS and the presence of NAFLD (Ptrend = 0·009). The OR (95 % CI) of NAFLD for quintiles 2–5 were 0·78 (0·62, 0·98), 0·74 (0·59, 0·94), 0·69 (0·55, 0·86) and 0·77 (0·61, 0·97), respectively. Path analyses indicated that a higher DASH-DS was associated with lower serum RBP4, hs-CRP, TAG, HOMA-IR and BMI, which were positively associated with the degree of NAFLD.
Adherence to the DASH diet was independently associated with a marked lower prevalence of NAFLD in Chinese adults, especially in women and those without abdominal obesity, and might be mediated by reducing RBP4, hs-CRP, TAG, HOMA-IR and BMI.
The present study was performed on antigen-presenting cells (APCs) of Theileria annulata transformed dendritic cells (TaDCs) and monocyte-derived dendritic cells (MoDCs) to compare differences in antigen presentation and stimulation of T lymphocyte proliferation. Antigen presentation for T lymphocyte proliferation was analysed by flow cytometry. Additionally, the level of mRNA transcription of small GTPases of the Rab family expressed in the TaDC cell line was analysed by quantitative real-time polymerase chain reaction (Q-RT-PCR). The endocytosis rate of TaDCs was significantly (P < 0.01) lower than in MoDCs. In contrast, when T lymphocytes were co-cultured with TaDC-APCs T cell proliferation was similar, while co-culture with MoDC-APC stimulated proliferation of CD4+ cells to a greater degree than CD8+ cells. However, the efficacy of TaDC-APCs to stimulate T lymphocytes dropped as the number of passages of TaDC-APC increased. Likewise, the transcription level of Rab family genes also significantly (P > 0.001) declined with progressive passages (>50) of the TaDC cell line. We conclude that initially the TaDC cell line efficiently presents antigen to stimulate T lymphocyte proliferation to produce a cellular immune response against the presented antigen.
The effect of maternal folate intake on small-for-gestational-age (SGA) births remains inconclusive. The present study aimed to investigate the associations of maternal folate intake from diet and supplements with the risk of SGA births using data from a cross-sectional study in Shaanxi Province of Northwest China. A total of 7307 women who were within 12 months (median 3; 10th–90th percentile 0–7) after delivery were included. Two-level models were adopted to examine the associations of folate (dietary folate, supplemental folic acid and total folate) intake with the risk of SGA births and birth weight Z score, controlling for a minimum set of confounders that were identified in a directed acyclic graph. Results showed that a higher supplemental folic acid intake during the first trimester was negatively associated with the risk of SGA births (≤60 d v. non-use: OR 0·80; 95 % CI 0·66, 0·96; >60 d v. non-use: OR 0·78; 95 % CI 0·65, 0·94; Ptrend = 0·010; per 10-d increase: OR 0·97; 95 % CI 0·95, 0·99). A higher total folate intake during pregnancy was associated with a reduced risk of SGA births (highest tertile v. lowest tertile: OR 0·77; 95 % CI 0·64, 0·94; Ptrend = 0·010; per one-unit increase in the log-transformed value: OR 0·81; 95 % CI 0·69, 0·95). A similar pattern was observed for the birth weight Z score. Our study suggested that folic acid supplementation during the first trimester and a higher total folate intake during pregnancy were associated with a reduced risk of SGA births.