Chromosome-scale genome assembly and annotation of Cotoneaster glaucophyllus.

Cotoneaster glaucophyllus is a semi-evergreen plant that blossoms in late summer, producing dense, attractive, fragrant white flowers with significant ornamental and ecological value. Here, a chromosome-scale genome assembly was obtained by integrating PacBio and Illumina sequencing data with the aid of Hi-C technology. The genome assembly was 563.3 Mb in length, with contig N50 and scaffold N50 values of ~6 Mb and ~31 Mb, respectively. Most (95.59%) of the sequences were anchored onto 17 pseudochromosomes (538.4 Mb). We predicted 35,856 protein-coding genes, 1,401 miRNAs, 655 tRNAs, 425 rRNAs, and 795 snRNAs. The functions of 34,967 genes (97.52%) were predicted. The availability of this chromosome-level genome will provide valuable resources for molecular studies of this species, facilitating future research on speciation, functional genomics, and comparative genomics within the Rosaceae family.

A new species of Sedum (Crassulaceae) from Mount Danxia in Guangdong, China.

Sedumjinglanii, a new species of Crassulaceae from Mount Danxia in Guangdong, China, is described and illustrated. Phylogenetic analysis based on the internal transcribed spacer (ITS) region of nrDNA suggests that the new species belongs to S.sect.Sedum sensu Fu and Ohba (2001) in the "Flora of China", and is sister to a clade comprising S.alfredi and S.emarginatum with high support values (SH-aLRT = 84, UFBS = 95) but is distantly related to S.baileyi. The new species is morphologically similar to S.alfredi but it can be distinguished from the latter in its opposite leaves (vs. alternate leaves), its usually wider leaves (0.4-1.2 cm vs. 0.2-0.6 cm), its usually shorter petals (3.4-4.5 mm vs. 4-6 mm), its shorter nectar scales (0.4-0.5 mm vs. 0.5-1 mm), its shorter carpels (1.5-2.6 mm vs. 4-5 mm), and its shorter styles (0.6-0.9 mm vs. 1-2 mm). The new species can be easily distinguished from S.emarginatum which both have opposite leaves by its short, erect or ascending rhizome (vs. long and prostrate rhizome in the latter), shorter petals (3.4-4.5 mm vs. 6-8 mm) and shorter carpels (1.5-2.6 mm vs. 4-5 mm). It can also be easily distinguished from S.baileyi by its short, erect or ascending rhizome (vs. long and prostrate rhizome) and its shorter style (0.6-0.9 mm vs. 1-1.5 mm).

Comparative analysis of complete Ilex (Aquifoliaceae) chloroplast genomes: insights into evolutionary dynamics and phylogenetic relationships.

BACKGROUND: Ilex (Aquifoliaceae) are of great horticultural importance throughout the world for their foliage and decorative berries, yet a dearth of genetic information has hampered our understanding of phylogenetic relationships and evolutionary history. Here, we compare chloroplast genomes from across Ilex and estimate phylogenetic relationships. RESULTS: We sequenced the chloroplast genomes of seven Ilex species and compared them with 34 previously published Ilex plastomes. The length of the seven newly sequenced Ilex chloroplast genomes ranged from 157,182 bp to 158,009 bp, and contained a total of 118 genes, including 83 protein-coding, 31 rRNA, and four tRNA genes. GC content ranged from 37.6 to 37.69%. Comparative analysis showed shared genomic structures and gene rearrangements. Expansion and contraction of the inverted repeat regions at the LSC/IRa and IRa/SSC junctions were observed in 22 and 26 taxa, respectively; in contrast, the IRb boundary was largely invariant. A total of 2146 simple sequence repeats and 2843 large repeats were detected in the 41 Ilex plastomes. Additionally, six genes (psaC, rbcL, trnQ, trnR, trnT, and ycf1) and two intergenic spacer regions (ndhC-trnV and petN-psbM) were identified as hypervariable, and thus potentially useful for future phylogenetic studies and DNA barcoding. We recovered consistent phylogenetic relationships regardless of inference methodology or choice of loci. We recovered five distinct, major clades, which were inconsistent with traditional taxonomic systems. CONCLUSION: Our findings challenge traditional circumscriptions of the genus Ilex and provide new insights into the evolutionary history of this important clade. Furthermore, we detail hypervariable and repetitive regions that will be useful for future phylogenetic and population genetic studies.

When tropical and subtropical congeners met: Multiple ancient hybridization events within Eriobotrya in the Yunnan-Guizhou Plateau, a tropical-subtropical transition area in China.

Global climate changes during the Miocene may have created ample opportunities for hybridization between members of tropical and subtropical biomes at the boundary between these zones. Yet, very few studies have explored this possibility. The Yunnan-Guizhou Plateau (YGP) in Southwest China is a biodiversity hotspot for vascular plants, located in a transitional area between the floristic regions of tropical Southeast Asia and subtropical East Asia. The genus Eriobotrya (Rosaceae) comprises both tropical and subtropical taxa, with 12 species recorded in the YGP, making it a suitable basis for testing the hypothesis of between-biome hybridization. Therefore, we surveyed the evolutionary history of Eriobotrya by examining three chloroplast regions and five nuclear genes for 817 individuals (47 populations) of 23 Eriobotrya species (including 19 populations of 12 species in the YGP), plus genome re-sequencing of 33 representative samples. We concluded that: (1) phylogenetic positions for 16 species exhibited strong cytonuclear conflicts, most probably due to ancient hybridization; (2) the YGP is a hotspot for hybridization, with 11 species showing clear evidence of chloroplast capture; and (3) Eriobotrya probably originated in tropical Asia during the Eocene. From the Miocene onwards, the intensification of the Eastern Asia monsoon and global cooling may have shifted the tropical-subtropical boundary and caused secondary contact between species, thus providing ample opportunity for hybridization and diversification of Eriobotrya, especially in the YGP. Our study highlights the significant role that paleoclimate changes probably played in driving hybridization and generating rich species diversity in climate transition zones.

Eriobotryacrassifolia (Rosaceae), a new species from Yunnan Province, China.

The new species Eriobotryacrassifolia, collected from Yunnan Province, China, is characterised and illustrated. A phylogeny based on chloroplast genomes supported its closest affinity with E.tengyuehensis, while a phylogeny based on 197 single-copy nuclear genes supported its closest affinity with E.fragrans and E.deflexa. Morphologically, however, it resembles E.angustissima. Nevertheless, it can be easily distinguished from E.angustissima by its abaxially retroflexed and sharply serrate leaf margins, densely rusty tomentose inflorescences, and oblong or elliptic leaves.

Phylogenomic analyses based on genome-skimming data reveal cyto-nuclear discordance in the evolutionary history of Cotoneaster (Rosaceae).

As a consequence of hybridization, polyploidization, and apomixis, the genus Cotoneaster (Rosaceae) represents one of the most complicated and controversial lineages in Rosaceae, with ca. 370 species which have been classified into two subgenera and several sections, and is notorious for its taxonomic difficulty. The infrageneric relationships and taxonomy of Cotoneaster have remained poorly understood. Previous studies have focused mainly on natural hybridization involving only several species, and phylogeny based on very limited markers. In the present study, the sequences of complete chloroplast genomes and 204 low-copy nuclear genes of 72 accessions, representing 69 species as ingroups, were used to conduct the most comprehensive phylogenetic analysis so far for Cotoneaster. Based on the sequences of complete chloroplast genomes and many nuclear genes, our analyses yield two robust phylogenetic trees respectively. Chloroplast genome and nuclear data confidently resolved relationships of this genus into two major clades which largely supported current classification based on morphological evidence. However, conflicts between the chloroplast genome and low-copy nuclear phylogenies were observed in both the species level and clade level. Cyto-nuclear discordance in the phylogeny could be caused by frequent hybridization events and incomplete sorting lineage (ILS). In addition, our divergence-time analysis revealed an evolutionary radiation of the genus from late Miocene to date.

Effect of ABCB1 3435C>T Genetic Polymorphism on Pharmacokinetic Variables of Tacrolimus in Adult Renal Transplant Recipients: A Systematic Review and Meta-analysis.

PURPOSE: Tacrolimus is the substrate of multidrug-resistance 1 (ABCB1). However, the effect of ABCB1 C3435T polymorphism on pharmacokinetic variables of tacrolimus is controversial in different studies. This meta-analysis was conducted to explore the relationship between ABCB1 3435C>T genetic polymorphism and pharmacokinetic variables of tacrolimus. METHODS: A database search was conducted of PubMed, EMBASE, Cochrane Library, and ClinicalTrials.gov, as well as Chinese databases (SinoMed, Wan Fang, and China National Knowledge Infrastructure). We also scanned reference lists and corresponded with authors. The study explored the relationship between ABCB1 3435C>T genetic polymorphism and pharmacokinetic variables of tacrolimus stratified according to time of posttransplantation, ethnicity, methods of concentration measurement, and the initial doses of tacrolimus. FINDINGS: Sixteen studies were included in this meta-analysis. In the subgroup analysis, ABCB1 3435TT had a significantly lower weight-adjusted dose than ABCB1 3435CC, which was not observed in the ABCB1 3435CT group. The subgroup analysis then revealed that the tacrolimus concentration/weight-adjusted daily dose ratio of ABCB1 3435T carriers was significantly higher than that of the ABCB1 3435CC group at 1 and 6 months. Meanwhile, ABCB1 3435CT and TT both had a higher tacrolimus concentration/weight-adjusted daily dose ratio compared with ABCB1 3435CC. IMPLICATIONS: Our meta-analysis identified that the ABCB1 3435C>T genetic polymorphism affected the pharmacokinetic variables of tacrolimus in adult renal transplant recipients. However, individualized treatments based on genetic polymorphisms require further investigation.

A new species of Eriobotrya (Rosaceae) from Yunnan Province, China.

Eriobotrya laoshanica, a new species of Rosaceae from Yunnan, China, is described and illustrated. The new species is easily distinguished from the most similar species E. malipoensis K. C. Kuan by its longer petioles (2-5 vs. 0.5-1 cm); indumentum on the lower leaf surfaces (densely tomentose vs. glabrous); much fewer flowers (15- to 30-flowered vs. 50- to 100-flowered) on the panicle; larger flowers (2.5-3 vs. 1.5-2 cm in diameter); and non-angulated (vs. angulated) young fruits.

Severe Plastid Genome Size Reduction in a Mycoheterotrophic Orchid, Danxiaorchis singchiana, Reveals Heavy Gene Loss and Gene Relocations.

Danxiaorchis singchiana (Orchidaceae) is a leafless mycoheterotrophic orchid in the subfamily Epidendroideae. We sequenced the complete plastome of D. singchiana. The plastome has a reduced size of 87,931 bp, which includes a pair of inverted repeat (IR) regions of 13,762 bp each that are separated by a large single copy (LSC) region of 42,575 bp and a small single copy (SSC) region of 17,831 bp. When compared to its sister taxa, Cremastra appendiculata and Corallorhiza striata var. involuta, D. singchiana showed an inverted gene block in the LSC and SSC regions. A total of 61 genes were predicted, including 21 tRNA, 4 rRNA, and 36 protein-coding genes. While most of the housekeeping genes were still intact and seem to be protein-coding, only four photosynthesis-related genes appeared presumably intact. The majority of the presumably intact protein-coding genes seem to have undergone purifying selection (dN/dS < 1), and only the psaC gene was positively selected (dN/dS > 1) when compared to that in Cr. appendiculata. Phylogenetic analysis of 26 complete plastome sequences from 24 species of the tribe Epidendreae had revealed that D. singchiana diverged after Cr. appendiculata and is sister to the genus Corallorhiza with strong bootstrap support (100%).

Evaluating climate and irrigation effects on spatiotemporal variabilities of regional groundwater in an arid area using EOFs.

Groundwater level is an important variable in the evolution process of ecological environment systems. However, spatiotemporal changes in groundwater level are attributed to the comprehensive influence of natural and anthropogenic activities. Therefore, understanding the major driving forces to changes in spatiotemporal patterns of groundwater level is essential for sustainable utilization of regional groundwater and sustaining healthy ecosystems, especially in arid areas. In this study, based on monthly observations of depth to groundwater table (DTGT) from 67 monitoring wells during 2001-2010 in the Yichang Irrigation Sub-district (YISD) of the Hetao Irrigation District (HID), which is located in Northwest China with an arid climate, the empirical orthogonal function (EOF) method was used to analyze the spatiotemporal variations of DTGT and the major driving forces. The EOF analysis results showed that the first two spatial structures (EOF1 and EOF2) of DTGT were found in this region, which explained over 65% and 8% of the spatial variation of DTGT, respectively. Meteorological factors (evaporation and temperature) were the first leading factors to drive the temporal pattern of the first expansion coefficient (EC1) corresponding to the EOF1 at intra-annual scale as well as inter-annual scale. Particularly, temperature controlled the EC1 pattern during the freezing period from December to March. Soil texture was shown to have good correlations with the spatial patterns of DTGT, although these correlations diminished when the depth exceeded 250 cm. This study provides strong evidence that the principal spatiotemporal variations of groundwater can be effectively extracted by the EOF method, thereby obtaining integrated views of the relationships between the groundwater system and meteorological and anthropogenic factors.

Saxifraga damingshanensis (S. sect. Irregulares, Saxifragaceae), a new species from Guangxi, China.

Saxifraga damingshanensis (Saxifragaceae), a new species from Damingshan Nature Reserve in Guangxi Province, is described and illustrated. A morphological comparison between the new species and its putative relatives, S. mengtzeana and S. luoxiaoensis, is presented. The new species is morphologically similar to S. mengtzeana, but it can be easily distinguished by its non-peltate leaf, both surfaces of mature leaf blade covered with white glandular trichome, petals 3-veined and margin entire. Phylogenetic analysis, based on two chloroplast DNA regions (matK and psbA-trnH), confirmed that the new species belongs to S. sect. Irregulares. The new species is currently only known from Damingshan, Guangxi and we assign it an IUCN Red List preliminary status as Data Deficient.

Development and characterization of genomic microsatellite markers in the tree species, Rhodoleia championii, R. parvipetala, and R. forrestii (Hamamelidaceae).

Rhodoleia Champion ex Hooker is one of the most primitive relict genera of Hamamelidaceae, a key family exploited to understand the origin and early evolution of flowering plants. Genomic simple sequence repeats (SSRs) were developed for R. championii to perform genetic diversity, phylogeographical structure or even systematic evolution studies of the genus. Among the 278,743 contigs (105,758,242 bps) de novo assembled from the low-coverage whole genome sequencing of R. championii, a total of 9106 SSRs were detected in 8370 contigs, and SSR primer pairs were successfully designed for 6677 SSRs. Among the 110 selected primer pairs, 41 were amplified successfully in the preliminary test of SSR screening. Further amplification of these 41 primer pairs across the 122 individuals collected from six populations of the three Rhodoleia species showed that 32 and 40 SSR markers can be amplified in Vietnam and Jinping populations of R. parvipetala, 41, 33, and 41 SSR markers in Boluo, Hongkong and Xinyi populations of R. championii, 25 SSR markers in Fugong population of R. forrestii, and 20 SSR markers demonstrated to be polymorphic across the three species. Genetic analysis for these 20 polymorphic SSRs showed that Allele number (A) ranged from four to 13 and polymorphic information content (PIC) ranged from 0.479 to 0.876 across the three species. At the population level, observed heterozygosity (HO) ranged from 0.000 to 1.000, and expected heterozygosity (HE) ranged from 0.091 to 0.851. In the present study, we provided the first whole-genome sequencing database for the species R. championii, identified ample SSR loci with designed primers, and revealed that 20 of the 110 selected SSRs were polymorphic across three Rhodoleia species. These provide valuable resources for future studies on genetic study, species delimitation, phylogeography, and conservation of this genus.

Isolation and identification of EST-SSR markers in Ixonanthes chinensis (Ixonanthaceae).

PREMISE: Ixonanthes (Ixonanthaceae) consists of between three and 19 species, among which I. chinensis and I. khasiana are considered vulnerable. Here, 58 microsatellite markers were developed for further conservation of these two Ixonanthes species. METHODS AND RESULTS: RNA transcripts of I. chinensis were sequenced and assembled into 19,545 unigenes, and 994 simple sequence repeat (SSR) loci were identified from 920 contigs. Based on these, 106 primer pairs were designed, 58 were successfully amplified, and 12 demonstrated polymorphism among five populations. The number of alleles per locus varied from three to 10, and the levels of observed and expected heterozygosity ranged from 0.000 to 1.000 and 0.000 to 0.844, respectively. Further assessment of the transferability of the 58 amplifiable primers reported 30 being successfully cross-amplified in I. icosandra and three in Erythroxylum sinense. CONCLUSIONS: These novel SSR markers will be useful for future genetic conservation studies on these Ixonanthes species.

Identification and development of microsatellite (SSRs) makers of Exbucklandia (HAMAMELIDACEAE) by high-throughput sequencing.

Hamamelidaceae (Saxifragales, previously Rosales) comprises approximately six subfamily, 30 genera and 140 species, most of which are Tertiary relicts. Exbucklandia is the only genus of the subfamily Exbucklandioideae, Hamelidaceae, containing only 2-4 species. Of them, the species E. longipetala H. T. Chang is endemic to China and listed as endangered in The Biodiversity Red List of China: Higher Plant, yet some taxonomists put forward that E. longipetala should be merged into E. tonkinensis (Lecomte) H. T. Chang. Currently, there was nearly no phylogeographic studies on this genus possibly due to the deficiency of efficient molecular markers. In this study, we sequenced the genome of E. tonkinensis based on high throughput sequencing technology, and obtained approximately 6 G raw data, which was further de novo assembled into 303,481 contigs. Based on them, 15,326 SSRs were identified from 13,596 contigs, and primers were successfully designed for 10,660 SSRs. A total of 139 paired primers were synthesized, 106 of them were successfully amplified in six Exbucklandia individuals with expected PCR product size, and 24 demonstrated to be polymorphic among three Exbucklandia populations. Accordingly, the expected and observed heterozygosity were between 0.097-0.717 and 0.098-0.583. Based on these efforts, future researches on genetic diversity and population structure of Exbucklandia can be performed to understand its phylogenetic origins and phylogeographic pattern.

Predictive value of platelet aggregation rate in postpartum deep venous thrombosis and its possible mechanism.

The present study investigated the predictive value of the platelet aggregation rate in postpartum deep venous thrombosis and its possible mechanism. From January 2014 to January 2016, 23 patients with postpartum deep vein thrombosis of lower extremity treated in the Department of Obstetrics of Beijing Chaoyang Hospital were as assigned as the observation group. At the same time, 25 cases with normal recovery were assigned as the control group. Blood samples were collected from all the subjects. The platelet aggregation rate was measured using a platelet aggregation apparatus. Plasma platelet activating factor (PAF) levels were measured by ELISA. The positive rate of platelet P-selectin (CD62p) and lysosomal membrane glycoprotein (CD63) was measured by flow cytometry. PI3K expression and AKt phosphorylation levels were measured by western blot analysis. The ROC curve was used to evaluate the value of the platelet aggregation rate in predicting postpartum deep vein thrombosis of lower extremity. The correlation between the platelet aggregation rate and PAF and PI3K/AKt expression was also analyzed. The cesarean section rate, platelet 5-min maximum aggregation rate, PAF level and the positive rate of CD62p and CD63 were significantly higher in the control than those in the observation group (P<0.05). Furthermore, the platelet aggregation rate was positively correlated with the expression of PAF, CD62p and CD63 (r=0.389, 0.451, and 0.452; all P<0.05). The platelet 5-min maximum aggregation rate for predicting postpartum deep vein thrombosis of lower extremity was reflected by the area under the ROC curve (AUC=0.797, P=0.000). The PI3Kp110ß/ß-actin and p-AKt/AKt ratio was significantly higher in the observation compared with the control group (P<0.05). In addition, the platelet aggregation rate was positively correlated with the expression of PI3K and phosphorylation level of AKt (r=0.441, 0.430; all P<0.05). The results suggested that platelet aggregation activity is elevated in postpartum deep vein thrombosis patients. It has a certain predictive value for the occurrence of postpartum deep vein thrombosis of lower extremity. Thuss, the PI3K/AKt signaling pathway may be one of the mechanisms of platelet aggregation.

Development and characterization of genomic SSR markers for Anneslea fragrans (Pentaphylacaceae).

PREMISE OF THE STUDY: The genus Anneslea (Pentaphylacaceae) contains four species and six varieties, most of which are locally endemic. Here, simple sequence repeat (SSR) markers were developed for the conservation of these species. METHODS AND RESULTS: The genome of A. fragrans was sequenced and de novo assembled into 445,162 contigs, of which 30,409 SSR loci were detected. Primers for 100 SSR loci were validated with PCR amplification in three populations of A. fragrans. Seventy-nine loci successfully amplified, and 30 were polymorphic. The mean number of alleles, observed heterozygosity, and expected heterozygosity were 7.01 ± 1.60, 0.817 ± 0.241, and 0.796 ± 0.145, respectively. Most primers could be amplified in Ternstroemia gymnanthera, T. kwangtungensis, and Cleyerapachyphylla. CONCLUSIONS: Our study demonstrated that shotgun genome sequencing is an efficient way to develop genomic SSR markers for nonmodel species. These genomic SSR loci will be valuable in population genetic studies in Anneslea and its relatives.

Development and validation of EST-SSR markers for Fokienia hodginsii (Cupressaceae).

PREMISE OF THE STUDY: Fokienia hodginsii (Cupressaceae) is a Tertiary relict evergreen conifer of the monotypic genus Fokienia. Polymorphic microsatellite markers were developed to investigate its genetic diversity and population structure. METHODS AND RESULTS: RNA transcripts of F. hodginsii were sequenced and de novo assembled into 85,818 unigenes, and 1892 simple sequence repeat (SSR) markers were detected from the unigenes. A total of 273 expressed sequence tag-SSR primer pairs were designed and tested, and 129 successfully amplified. Eleven displayed clear polymorphisms in F. hodginsii. Amplification of these polymorphic primers across three populations of F. hodginsii showed the number of alleles per locus ranged from two to seven, and the expected heterozygosity per locus varied from 0.067 to 0.847. All 11 polymorphic primers amplified in Thuja occidentalis, while 10 amplified in T. standishii, Platycladus orientalis, and Chamaecyparis obtusa. CONCLUSIONS: These microsatellite markers will be useful in exploring genetic diversity of F. hodginsii and other conifer trees.

Isolation and identification of EST-SSR markers in Chunia bucklandioides (Hamamelidaceae).

PREMISE OF THE STUDY: Chunia bucklandioides (Hamamelidaceae), endemic to Hainan, China, is listed as threatened in the IUCN Red List and is now only found on Mt. Diaoluo and Mt. Jianfeng. Thus, microsatellite markers were developed for future conservation genetic studies of this species. METHODS AND RESULTS: A total of 115 primers were designed on the basis of the transcriptome data of C. bucklandioides. Of them, 59 successfully amplified in C. bucklandioides and polymorphisms were detected in 11; the number of alleles per locus varied from two to five, the observed heterozygosity ranged from 0.000 to 0.941, and the expected heterozygosity ranged from 0.000 to 0.699. A total of 13 primers amplified in Mytilaria laosensis, and five primers amplified in Exbucklandia tonkinensis and E. populnea. CONCLUSIONS: The markers screened here provide a basis to assess genetic structure and further establish conservation strategies for C. bucklandioides.

Development and characterization of EST-SSR markers for Artocarpus hypargyreus (Moraceae).

PREMISE OF THE STUDY: Polymorphic microsatellite markers were developed for Artocarpus hypargyreus (Moraceae), a threatened species endemic to China, to investigate the genetic diversity and structure of the species. METHODS AND RESULTS: Based on the transcriptome data of A. hypargyreus, 63 primer pairs were preliminarily designed and tested, of which 34 were successfully amplified and 10 displayed clear polymorphisms across the 67 individuals from four populations of A. hypargyreus. The results showed the number of alleles per locus ranged from three to 10, and the observed heterozygosity and expected heterozygosity per locus varied from 0.000 to 0.706 and from 0.328 to 0.807, respectively. CONCLUSIONS: These microsatellite markers will be useful in exploring genetic diversity and structure of A. hypargyreus. Furthermore, most loci were successfully cross-amplified in A. nitidus and A. heterophyllus, indicating that they will be of great value for genetic study across this genus.

Incidence of venous thromboembolism during pregnancy and the puerperium: a systematic review and meta-analysis.

OBJECTIVE: Women during pregnancy or puerperium have a higher risk of venous thromboembolism (VTE). The reported incidence of pregnancy-associated VTE from literature varied considerably. To summarize the overall incidence of the disease, we conducted this meta-analysis. METHODS: We searched PubMed, EMBase and CNKI (China National Knowledge Infrastructure) for studies that reported the incidence of VTE during pregnancy or puerperium. The quality of included studies was assessed using the Newcastle-Ottawa scale and the meta-analysis was conducted using R software and Meta analyst Beta 3.13. Sensitivity analyses were performed to analyze the robustness of the results and publication bias was assessed using Egger's test. RESULTS: Twenty-seven articles met the inclusion criteria. The pooled incidence rate was 1.4‰ (1.0-1.8‰) for VTE, 1.1‰ (1.0-1.3‰) for deep vein thrombosis (DVT) and 0.3‰ (0.2-0.4‰) for pulmonary embolism (PE). The weighted proportion of VTE postpartum was 57.5% and the pooled proportion of right-sided DVT was 27.9%. We noted substantial heterogeneity among individual studies. CONCLUSIONS: Women during pregnancy or puerperium are associated with a higher morbidity of VTE. Physicians should be of high vigilance to pregnancy-associated VTE, especially for women postpartum.