Previous studies have shown that mothers of naturally conceived dizygotic (DZ) twins tend to be taller, older, and smoke more than mothers of naturally conceived monozygotic (MZ) twin and mothers of singletons. Here, we investigate whether mothers of naturally conceived DZ twins differ from mothers who conceived their DZ twins after medically assisted reproduction (MAR) in eight maternal traits related to fertility based on observational survey data. We include data from 33,648 mothers from the Netherlands Twin Register (NTR) and 1660 mothers of twins from the Norwegian Mother, Father and Child Cohort Study (MoBA). We contrast mothers of naturally conceived DZ twins with mothers of MAR DZ twins. Next, we further segment the MAR group into mothers who underwent hormonal induction of ovulation but not in vitro fertilization (IVF) and those who IVF twins, comparing them both to each other and against the mothers of naturally conceived DZ twins. Mothers of naturally conceived DZ twins smoke more often, differ in body composition, have a higher maternal age and have more offspring before the twins than mothers of MZ twins. Compared to MAR DZ twin mothers, mothers of naturally conceived DZ twins have fewer miscarriages, lower maternal age and increased height, more offspring and are more often smokers. BMI before the twin pregnancy is similar in both natural and MAR DZ twin mothers. Mothers who received hormonal induction of ovulation (OI) have a lower maternal age, fewer miscarriages, and a higher number of offspring before their twin pregnancy than twin mothers who received IVF and/or intracytoplasmic sperm injection (ICSI) treatments. Our study shows that twin mothers are a heterogenous group and the differences between twin mothers should be taken into account in epidemiological and genetic research that includes twins.

OBJECTIVE: Are authors aware when they have cited a retracted paper in their manuscripts in the medically assisted reproduction (MAR) field?
METHODS: A cross-sectional study based on an online survey was conducted to acquire information on the citation pattern from corresponding authors who had cited a retracted article. A dataset of retracted articles in the MAR field was collected from PubMed and Retraction Watch. A complete list of published articles that cited each retracted article was retrieved. The survey was distributed via e-mail to corresponding authors who had cited a retracted paper in their study.
RESULTS: The survey revealed a significant lack of awareness among authors, with 78.7% unaware that they had cited retracted articles. This lack of awareness was attributed to insufficient notification mechanisms within research databases and journals, alongside a reliance on previously stored copies of manuscripts. A notable finding was that reference checks were typically performed by a single author, with no instances of retraction concerns raised during the peer-review process. Only a small fraction (17.8%) of respondents reported verifying retraction notices on both journal websites and scientific databases.
CONCLUSIONS: Correcting publications that contain references which are subsequently retracted is significant for systematic reviews, meta-analyses and guidelines. Citations of retracted articles perpetuate erroneous scientific data, but assessing the accuracy of citations requires considerable effort. Proper notification of retraction status and cross-checking of citations can help to prevent errors.

UNASSIGNED: Preimplantation Genetic Testing (PGT) is a cutting-edge test used to detect genetic abnormalities in embryos fertilized through Medically Assisted Reproduction (MAR). PGT aims to ensure that embryos selected for transfer are free of specific genetic conditions or chromosome abnormalities, thereby reducing chances for unsuccessful MAR cycles, complicated pregnancies, and genetic diseases in future children.
UNASSIGNED: In PGT, genetics, embryology, and technology progress and evolve together. Biological and technological limitations are described and addressed to highlight complexity and knowledge constraints and draw attention to concerns regarding safety of procedures, clinical validity, and utility, extent of applications and overall ethical implications for future families and society.
UNASSIGNED: Understanding the genetic basis of diseases along with advanced technologies applied in embryology and genetics contribute to faster, cost-effective, and more efficient PGT. Next Generation Sequencing-based techniques, enhanced by improved bioinformatics, are expected to upgrade diagnostic accuracy. Complicating findings such as mosaicism, mt-DNA variants, variants of unknown significance, or variants related to late-onset or polygenic diseases will however need further appraisal. Emphasis on monitoring such emerging data is crucial for evidence-based counseling while standardized protocols and guidelines are essential to ensure clinical value and respect of Ethical, Legal and Societal Issues.

OBJECTIVE: To evaluate the relative impact of different strategies of medically assisted reproduction (MAR), i.e. first line treatment (ovarian stimulation with or without intrauterine insemination) and in vitro fertilization (IVF) procedures (conventional IVF or intracytoplasmic sperm injection), on the risk of multiple births.
METHODS: We utilized the health care utilization databases of the Lombardy region to identify births resulting from MAR between 2007 and 2022. We gathered data on the total number of multiple births and calculated the prevalence rate by dividing the number of multiples by the total number of births. To examine the temporal trend in the proportion of multiple births after MAR over time, a linear regression model was employed separately for different types of techniques and in strata of maternal age.
RESULTS: A total of 30,900 births after MAR were included; 4485 (14.5 %) first line treatments and 26,415 (85.5 %) IVF techniques. Overall, 4823 (15.6 %) multiple births were identified. The frequency of multiple births over the study period decreased from 22.0 % in 2007 to 8.7 % in 2022 (p < 0.01). Multiple births from first line treatments were stable ranging from 13.5 % in 2007-2008 to 12.0 % in 2021-2022 (p = 0.29). Multiple births from IVF procedures decreased from 23.8 % in 2007-2008 to 8.4 % in 2021-2022 (p < 0.01). Stratifying for maternal age (i.e. < 35 and ≥ 35 years), the trends remained consistent.
CONCLUSIONS: The reduction in multiple births has been influenced by changes in IVF strategy and procedures. The decline has been gradual but steady since 2009, when a law restricting embryo freezing was repealed in Italy. In contrast, the proportion of multiple births resulting from first line treatments has remained constant over time. Despite declining, multiple births from MAR remained about one order of magnitude higher than those from spontaneous pregnancies.

Following the advancement of medically assisted reproduction (MAR) technology, and the rationale to extend the culture to the blastocyst stage, performing elective single embryo transfer (eSET), gamete quality and assessment have acquired large relevance in ART. Embryo quality is strictly correlated with gametes quality and culture conditions. Oocyte maturity assessment is therefore imperative for fertilization and embryo evolution. Mature oocytes at the metaphase II stage result in a higher fertilization rate compared to immature oocytes. Indeed, oocyte morphology evaluation represents an important and challenging task that may serve as a valuable prognostic tool for future embryo development and implantation potential. Different grading systems have been reported to assess human embryos, however, in many cases, it is still a major challenge to select the single embryo to transfer with the highest implantation potential. Further, eSET has conferred a challenge to embryologists, who must try to enhance embryo culture and selection to provide an adequate success rate, whilst reducing the overall number of embryos transferred. Above the standard morphological assessment, there are several invasive or non-invasive approaches for embryo selection such as preimplantation genetic testing, time-lapse technology, proteomics and metabolomics, as well as oxygen utilization and analysis of oxidative stress in culture medium. This short review is not designed to be a comprehensive review of all possible features that may influence oocyte quality. It does give, however, a brief overview and describes the prognostic value of the morphological characteristics of human oocytes on their developmental capacity following ART treatments.

OBJECTIVE: To study educational gradients in births after medically assisted reproduction across 5 countries with different institutional arrangements.
METHODS: We use logistic regression and compute predicted probabilities to estimate the association between education and giving birth after assisted reproduction, before and after adjustment for maternal age at delivery and marital/partnership status, using an overall sample of about 3.9 million live births in 5 countries.
METHODS: Not applicable.
METHODS: This study includes survey or register data containing information on births in 5 countries: N = 61,564 for Denmark, N = 37,533 for France, N = 12,889 for Spain, N = 17,097 for the United Kingdom, and N = 3,700,442 for the United States.
UNASSIGNED: None.
METHODS: The probability of a child being born after medically assisted reproduction for mothers with a university degree relative to those having less than a university degree.
RESULTS: University-educated mothers are more likely to give birth after assisted reproduction compared with mothers with lower levels of education. After adjustment for socio-demographic characteristics, educational differences disappear in the United Kingdom and to some extent Spain, whereas they attenuate but persist in the other countries. The United States seems to show a larger educational gradient.
CONCLUSIONS: The results suggest that the institutional setting around assisted reproduction may moderate the gradient. A possible explanation may be access to treatments, as the United States - the context with the lowest subsidization - seems to show larger educational gradients than other contexts. In the context of global postponement of childbearing to older ages, mothers with lower levels of socioeconomic resources might find it more difficult to fully realize their fertility intentions in countries with less generous subsidization of treatments.

One-carbon (1-C) metabolic deficiency impairs homeostasis, driving disease development, including infertility. It is of importance to summarize the current evidence regarding the clinical utility of 1-C metabolism-related biomolecules and methyl donors, namely, folate, betaine, choline, vitamin B12, homocysteine (Hcy), and zinc, as potential biomarkers, dietary supplements, and culture media supplements in the context of medically assisted reproduction (MAR). A narrative review of the literature was conducted in the PubMed/Medline database. Diet, ageing, and the endocrine milieu of individuals affect both 1-C metabolism and fertility status. In vitro fertilization (IVF) techniques, and culture conditions in particular, have a direct impact on 1-C metabolic activity in gametes and embryos. Critical analysis indicated that zinc supplementation in cryopreservation media may be a promising approach to reducing oxidative damage, while female serum homocysteine levels may be employed as a possible biomarker for predicting IVF outcomes. Nonetheless, the level of evidence is low, and future studies are needed to verify these data. One-carbon metabolism-related processes, including redox defense and epigenetic regulation, may be compromised in IVF-derived embryos. The study of 1-C metabolism may lead the way towards improving MAR efficiency and safety and ensuring the lifelong health of MAR infants.

OBJECTIVE: Does medically assisted reproduction (MAR) use among cisgender women differ among those with same-sex partners or lesbian/bisexual identities compared to peers with different-sex partners or heterosexual identities?
CONCLUSIONS: Women with same-sex partners or lesbian/bisexual identities are more likely to utilize any MAR but are no more likely to use ART (i.e. IVF, reciprocal IVF, embryo transfer, unspecified ART, ICSI, and gamete or zygote intrafallopian transfer) compared to non-ART MAR (i.e. IUI, ovulation induction, and intravaginal or intracervical insemination) than their different-sex partnered and completely heterosexual peers.
BACKGROUND: Sexual minority women (SMW) form families in myriad ways, including through fostering, adoption, genetic, and/or biological routes. Emerging evidence suggests this population increasingly wants to form genetic and/or biological families, yet little is known about their family formation processes and conception needs.
METHODS: The Growing Up Today Study is a US-based prospective cohort (n = 27 805). Participants were 9-17 years of age at enrollment (1996 and 2004). Biennial follow-up is ongoing, with data collected through 2021.
METHODS: Cisgender women who met the following criteria were included in this sample: endorsed ever being pregnant; attempted a pregnancy in 2019 or 2021; and endorsed either a male- or female-sex partner OR responded to questions regarding their sexual identity during their conception window. The main outcome was any MAR use including ART (i.e. procedures involving micromanipulation of gametes) and non-ART MAR (i.e. nonmanipulation of gametes). Secondary outcomes included specific MAR procedures, time to conception, and trends across time. We assessed differences in any MAR use using weighted modified Poisson generalized estimating equations.
RESULTS: Among 3519 participants, there were 6935 pregnancies/pregnancy attempts and 19.4% involved MAR. A total of 47 pregnancies or pregnancy attempts were among the same-sex partnered participants, while 91 were among bisexual participants and 37 among lesbian participants. Participants with same-sex, compared to different-sex partners were almost five times as likely to use MAR (risk ratio [95% CI]: 4.78 [4.06, 5.61]). Compared to completely heterosexual participants, there was greater MAR use among lesbian (4.00 [3.10, 5.16]) and bisexual (2.22 [1.60, 3.07]) participants compared to no MAR use; mostly heterosexual participants were also more likely to use ART (1.42 [1.11, 1.82]) compared to non-ART MAR. Among first pregnancies conceived using MAR, conception pathways differed by partnership and sexual identity groups; differences were largest for IUI, intravaginal insemination, and timed intercourse with ovulation induction. From 2002 to 2021, MAR use increased proportionally to total pregnancies/pregnancy attempts; ART use was increasingly common in later years among same-sex partnered and lesbian participants.
CONCLUSIONS: Our results are limited by the small number of SMW, the homogenous sample of mostly White, educated participants, the potential misclassification of MAR use when creating conception pathways unique to SMW, and the questionnaire\'s skip logic, which excluded certain participants from receiving MAR questions.
CONCLUSIONS: Previous studies on SMW family formation have primarily focused on clinical outcomes from ART procedures and perinatal outcomes by conception method, and have been almost exclusively limited to European, clinical samples that relied on partnership data only. Despite the small sample of SMW within a nonrepresentative study, this is the first study to our knowledge to use a nonclinical sample of cisgender women from across the USA to elucidate family formation pathways by partnership as well as sexual identity, including pathways that may be unique to SMW. This was made possible by our innovative approach to MAR categorization within a large, prospective dataset that collected detailed sexual orientation data. Specifically, lesbian, bisexual, and same-sex partnered participants used both ART and non-ART MAR at similar frequencies compared to heterosexual and different-sex partnered participants. This may signal differential access to conception pathways owing to structural barriers, emerging conception trends as family formation among SMW has increased, and a need for conception support beyond specialized providers and fertility clinics.
BACKGROUND: The research reported in this publication was supported by the National Institute on Minority Health and Health Disparities of the National Institutes of Health (NIH), under award number R01MD015256. Additionally, KRSS is supported by NCI grant T32CA009001, AKH by the NCI T32CA057711, PC by the NHLBI T32HL098048, BM by the Stanford Maternal Child Health Research Institute Clinical Trainee Support Grant and the Diversity Fellowship from the American Society for Reproductive Medicine Research Institute, BGE by NICHD R01HD091405, and SM by the Thomas O. Pyle Fellowship through the Harvard Pilgrim Health Care Foundation and Harvard University, NHLBI T32HL098048, NIMH R01MH112384, and the William T. Grant Foundation grant number 187958. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. The first author recently had a leadership role in the not-for-profit program, The Lesbian Health Fund, a research fund focused on improving the health and wellbeing of LGBTQ+ women and girls. The fund did not have any role in this study and the author\'s relationship with the fund did not bias the findings of this manuscript.
BACKGROUND: N/A.

OBJECTIVE: There has been an increase in the number of single women deciding to have children through the use of medically assisted reproduction (MAR). These women are referred to as \'single mothers by choice\' (SMC).
BACKGROUND: Previous studies have shown how SMC can feel stigmatised.
OBJECTIVE: Explore if single women seeking fertility treatment in Denmark feel stigmatised.
METHODS: Six single women undergoing MAR at a public fertility clinic in Denmark were interviewed. The interviews were audiotaped, anonymised, and transcribed in full, after provided written consent by the participants to take part in the study. Data were analysed using qualitative content analysis.
RESULTS: The women would have preferred to have a child in a relationship with a partner. Despite their dream of the nuclear family meaning a family group consisting of two parents and their children (one or more), the women choose to become SMC because motherhood was of such importance, and they feared they would otherwise become too old to have children. The participants did not experience stigma or negative responses to their decision, but they all had an awareness of the prejudices other people might have towards SMC.
CONCLUSIONS: This study contributes to the understanding of the experiences of single women seeking fertility treatment in a welfare state where there are no differences in the possibilities for different social classes to seek MAR.

Almost all countries and fertility clinics impose age limits on women who want to become pregnant through Assisted Reproductive Technologies (ART). Age limits for aspiring fathers, however, are much less common and remain a topic of debate. This article departs from the principle of reproductive autonomy and a conditional positive right to receive ART, and asks whether there are convincing arguments to also impose age limits on aspiring fathers. After considering three consequentialist approaches to justifying age limits for aspiring fathers, we take in a concrete normative stance by concluding that those are not strong enough to justify such cut-offs. We reinforce our position by drawing a comparison between the case of a 39-year-old woman who wants to become a single mother via a sperm donor on the one hand, and on the other hand the same woman who wants to have a child with a 64-year-old man who she loves and who is willing to care for the child as long as he is able to. We conclude that, as long as appropriate precautions are taken to protect the welfare of the future child, couples who want to receive fertility treatment should never be limited on the basis of the age of the (male) partner. An absence of age limits for men would respect the reproductive autonomy of both the man and the woman.