Search

Background: Frozen embryo transfer (FET) has become a widely employed assisted reproductive technology technique. There have historically been concerns regarding the long-term metabolic safety of FET technology in offspring due to pregnancy-induced hypertension and large for gestational age, both of which are well-recognized factors for metabolic dysfunction of children. Therefore, we aimed to compare the metabolic profiles of children born after frozen versus fresh embryo transfer at 2 to 5 years of age., Methods and Findings: This was a prospective cohort study. Using data from the "Assisted Reproductive Technology borned KIDs (ARTKID)," a birth cohort of offspring born from assisted reproductive technology at the Institute of Women, Children and Reproductive Health, Shandong University, China. We included 4,246 singletons born after FET (n = 2,181) and fresh embryo transfer (n = 2,065) enrolled between 2008 and 2019 and assessed the glucose and lipid variables until the age of 2 to 5 years. During a mean follow-up of 3.6 years, no significant differences were observed in fasting blood glucose, fasting insulin, Homeostatic Model Assessment of Insulin Resistance Index, total cholesterol, triglycerides, low-density lipoprotein-cholesterol, and high-density lipoprotein-cholesterol levels between offspring conceived by fresh and frozen embryo transfer in the crude model and adjusted model (adjusted for parental age, parental body mass index, parental education level, paternal smoking, parity, offspring age and sex). These results remained consistent across subgroup analyses considering offspring age, the stage of embryo transfer, and the mode of fertilization. Results from sensitivity analysis on children matched for age within the cohort remains the same. The main limitation of our study is the young age of the offspring., Conclusions: In this study, the impact of FET on glucose and lipid profiles during early childhood was comparable to fresh embryo transfer. Long-term studies are needed to evaluate the metabolic health of offspring born after FET., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Zhou et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

STUDY QUESTION What are the factors influencing the occurrence of monozygotic (MZ) twins in offspring conceived by assisted reproductive technology (ART)? SUMMARY ANSWER Parental ages, the transfer of fresh versus frozen embryos, and the grade of blastocysts are all related to MZ twinning in ART offspring. WHAT IS KNOWN ALREADY Offspring conceived by ART have significantly increased risk of MZ twins, which may be due to the characteristics of the infertile population. The objective of this study was to explore the incidence of monozygotic (MZ) twins after ART and to clarify the risk factors for MZ twinning. STUDY DESIGN, SIZE, DURATION A total of 255 monozygotic twins were enrolled in this cohort study, and then matched with singletons at a ratio of 1:4 randomly (with 1020 in the control group). All offspring were conceived by single embryo transfer. PARTICIPANTS/MATERIALS, SETTING, METHODS The collected data were divided into the following three aspects for analysis: characteristics of the infertile population, gamete or embryo manipulations, and factors related to embryo development. MAIN RESULTS AND THE ROLE OF CHANCE The incidence of MZ twins was 1.638% (255 out of 15 567 pregnancies after single embryo transfers). Compared to singleton births, a significantly lower rate of frozen embryo transfers (FET; 78.0% vs 86.1% P  = 0.002) was seen amongst the MZ twins. Amongst fresh ETs, the rate of blastocyst transfers in the MZ twins group was higher compared to that in the control group (92.9% vs 75.4%, P  = 0.005). We also found that certain grades of blastocysts in terms of trophectoderm (TE) development, inner cell mass + TE development and the classification of 'top-quality' embryos were associated with the incidence of MZ twinning (P  = 0.025, P  = 0.012, P  = 0.020, respectively). Logistic regression analysis revealed that higher paternal age (odds ratio (OR) = 0.94, 95% CI = 0.89–1.00, P  = 0.029) and FET (OR = 0.48, 95% CI = 0.33–0.68, P  = 0.001) may be protective factors against MZ twinning. However, higher maternal age (OR = 1.07, 95% CI = 1.01–1.13, P  = 0.027) and the transfer of blastocysts (OR = 4.31, 95% CI = 1.46–12.73, P  = 0.008) appeared to be associated with an increased risk of MZ twinning. Amongst blastocyst transfers, a C grade TE may be protective factor against MZ twinning (B: OR = 1.90, 95% CI = 1.18–3.07, P  = 0.009; A: OR = 1.58, 95% CI = 0.93–2.67, P  = 0.089). LIMITATIONS, REASONS FOR CAUTION First, our definition of MZ twins was based on twins' birth after single embryo transfers (SET), rather than ultrasound examination during early pregnancy. Second, the parental characteristics of the two groups were homogenous, so it was difficult to find any associations between infertility factors and the incidence of MZ twins. WIDER IMPLICATIONS OF THE FINDINGS This multifaceted analysis of the risk factors for MZ twinning provides some information for clinical interventions in high-risk populations. STUDY FUNDING/COMPETING INTEREST(S) This study was supported by the National Key Technology Research and Developmental Program of China (2022YFC2704404), CAMS Innovation Fund for Medical Sciences (2021-I2M-5-001), Taishan Scholars Program for Young Experts of Shandong Province (tsqn201909195), the Basic Science Center Program (31988101), and the Shandong Provincial Key Research and Development Program (2020ZLYS02). All authors have no conflicts of interest to declare. TRIAL REGISTRATION NUMBER N/A. [ABSTRACT FROM AUTHOR]

Purpose: To study the associations between fetal fraction at the first trimester and subsequent adverse pregnancy outcomes (APOs) in IVF singleton pregnancies with single embryo transfer from frozen cycles. Methods: This is a single-center retrospective cohort study on IVF singleton pregnancies with single embryo transfer from frozen cycles. A total of 8457 women were collected between March 2015 and September 2018 from the Center for Reproductive Medicine, Shandong University, China. Participants underwent cell-free DNA (cfDNA) sequencing at 11–13 weeks' gestation. Multivariable logistic regressions were performed with the risk of APOs based on various predictor variables. Results: A total of 8457 women were included in the analysis of which 1563 (18.48%) women developed one or more APOs. The hypertensive disorders of pregnancy (HDP) (N = 515), gestational diabetes mellitus (GDM) (N = 684), preterm birth (PTB) (N = 567), and low birth weight (LBW) (N = 306) groups had lower fetal fraction compared with the no pregnancy complication (NPC) group (all p values < 0.05). Based on the multivariable logistic regression results, the optimal cutoff values of fetal fraction were 9.30%, 12.54%, 9.10%, 12.65%, and 13.83% for at least one APO, HDP, GDM, PTB, and LBW, respectively. After adjustment for potential maternal confounders, women in the low fetal fraction (LFF) group had a higher risk for the APOs compared with high fetal fraction (HFF) group. Conclusions: The fetal fraction in HDP, GDM, PTB, and LBW groups were lower than NPC group in IVF singleton pregnancies with single embryo transfer from frozen cycles in China. [ABSTRACT FROM AUTHOR]