Although chromosomal mosaic embryos detected by trophectoderm(TE)biopsy offer healthy embryos available for transfer,high-resolution postnatal karyotyping and chromosome testing of the transferred embryos are insufficient.Here,we applied single-cell multi-omics sequenc-ing for seven infants with blastula chromosomal mosaicism detected by TE biopsy.The chromo-some ploidy was examined by single-cell genome analysis,with the cellular identity being identified by single-cell transcriptome analysis.A total of 1616 peripheral leukocytes from seven infants with embryonic chromosomal mosaicism and three control ones with euploid TE biopsy were analyzed.A small number of blood cells showed copy number alterations(CNAs)on seem-ingly random locations at a frequency of 0％-2.5％per infant.However,none of the cells showed CNAs that were the same as those of the corresponding TE biopsies.The blastula chromosomal mosaicism may be fully self-corrected,probably through the selective loss of the aneuploid cells dur-ing development,and the transferred embryos can be born as euploid infants without mosaic CNAs corresponding to the TE biopsies.The results provide a new reference for the evaluations of trans-ferring chromosomal mosaic embryos in certain situations.

【Objective】 To understand factors associated with children′s attendance at nursery care institutions (NCIs) and the basic characteristics of the NCIs children were enrolled in, so as to provide scientific evidence for policymakers. 【Methods】 During November 2020 and January 2021, parents who visited the Department of Child Health Care in six selected maternal and children′s hospitals, as well as nearby NCIs in Zhejiang were invited to finish an online questionnaire. Information such as children′s sociodemographic characteristics, parents′ knowledge, attitude and practice regarding nursery and feeding, etc. were collected. A total of 1 756 questionnaires were collected. 【Results】 Compared to children who were not in NCIs, children enrolled in NCIs were older (94.4% of children ≥24 months vs. 30.1%, χ²=835.27), more likely to be from the local area (87.2% vs. 81.4%,χ²=12.25), more likely to have parents with a college degree (mother: 83.6% vs. 74.2%, χ²=35.29; father: 79.9% vs. 70.0%, χ²=27.01), had a higher prevalence of family annual income >200 000 CNY (49.5% vs. 28.2%, χ²=110.49), and were less likely to have their grandparents available to take care of them (16.7% vs. 26.8%, χ²=31.4) The difference all have great significant.(P<0.05). In a multivariate Logistic regression model, the older the child, the more likely they were to attend an NCI (for children aged 6 - 23 months, OR=6.70; for children aged 24 - 35 months, OR=134.03; and for children aged 36 - 42 months, OR=699.33; P<0.05). Family annual income was positively associated with children′s attendance at NCIs (for those earning 100 000 - 200 000 CNY/year, OR=1.63; for those earning 200 000 - 500 000 CNY/year, OR=2.96; and for those earning >500 000 CNY/year, OR=4.62, P<0.05). Conversely, the higher the level of grandparent involvement in daily care, the lower the attendance at NCIs (for children cared for by both parents and grandparents, OR=0.57; for those primarily cared for by grandparents, OR=0.26, P<0.05). For children who used to stay at NCIs, 82.8% stayed at institutions that only recruited children aged 0 - 3 years, 97.4% spent their whole day in NCIs, and 71.4% spent less than 3 000 CNY per month for NCI services. Additionally, over 95% of parents were satisfied with the food and care services in NCIs, as well as their children′s physical development in NCIs. However, 32.1% of NCIs were reported by parents as having no room for breastfeeding. 【Conclusions】 Children′s age, grandparent involvement in routine care, and family annual income are the main factors associated with children′s attendance at NCIs. There is a greater need for more affordable and community-based NCIs, particularly for children under 2 years old. Additionally, more attention should be paid to the quality surveillance, assessment and management of NCIs.