Children Conceived by Assisted Reproductive Technology Prone to Low Birth Weight, Preterm Birth, and Birth Defects: A Cohort Review of More Than 50,000 Live Births During 2011-2017 in Taiwan

Assisted reproductive technology (ART) is not an independent risk factor for breech presentation among singleton term births in Vienna, Austria

Assisted reproductive technologies (ARTs) such as in vitro fertilisation (IVF) and intracytoplasmic sperm injection (ICSI) are still discussed critically, as there is no consensus on whether these treatments could be the cause of risk factors for obstetric problems such as breech presentation. The aim of this study was to test the association between ART and breech presentation among 11920 singleton term births taking place in Vienna from 2010 to 2020. In this single-centre medical record-based study, data concerning the conception mode (spontaneous versus IVF or ICSI), child presentation, birth mode, newborn sex and size as well as age, height, weight, and reproductive history of the mother were included. Three hundred twenty-six newborns (2.7%) were conceived by IVF or ICSI, and 527 newborns (4.4%) were delivered in breech presentation. Breech presentation occurred in 7.6% of IVF/ICSI children but only in 4.3% of spontaneously conceived children (P = 0.019). ART increased the crude risk of breech presentation significantly (OR = 1.67; 95% CI 1.71 - 2.38). After adjusting for maternal age, height, number of previous births, smoking, and newborn sex, however, ART had no longer a significant impact on the risk of breech presentation. In contrast, breech presentation was significantly associated with higher maternal age as well as a lower number of previous births, but not with ART. This study shows that the adverse outcomes of IVF and ICSI pregnancies may not be due to the ART treatment alone but might also be due to the mostly higher age and lower parity of the mothers using ART.

Similar pregnancy outcomes from fresh and frozen donor oocytes transferred to gestational carriers: a SART database analysis isolating the effects of oocyte vitrification

PURPOSE

This work aimed to study clinical and neonatal outcomes of embryos derived from frozen compared to fresh donor oocytes in gestational carrier cycles.

METHODS

This is a retrospective cohort study using the Society for Assisted Reproductive Technology Clinic Outcome Reporting System database between 2014 and 2015, comprising of 1284 fresh transfer cycles to gestational carrier recipients of embryos resulting from fresh (n = 1119) and vitrified/thawed (n = 165) donor oocytes. Models were adjusted for gestational carrier age, preimplantation genetic testing (PGT-A), number of embryos transferred, multiple gestation, and fetal heart reduction. As our models were part of a larger analysis, intended parent BMI, smoking status, and parity were also adjusted for, but did not influence outcomes in this analysis.

RESULTS

There was no significant difference in probability of live birth rates when comparing embryos derived from fresh and frozen donor oocytes in gestational carrier cycles. There were also no significant differences in biochemical pregnancy losses or clinical miscarriage. There were no significant differences noted in low birthweight or high birthweight infants derived from fresh versus frozen donor oocyte after transfer into a gestational carrier.

CONCLUSIONS

The analysis of fresh and frozen donor oocytes in gestational carrier cycles provides the opportunity to assess for a possible effect of vitrification on the oocyte by controlling for differences in the uterine environment. We observed no significant differences in live birth, pregnancy loss, low birthweight or high birthweight infants when comparing fresh and frozen donor oocytes in gestational carrier cycles.

Long-term health risk of offspring born from assisted reproductive technologies

Since the world's first in vitro fertilization baby was born in 1978, there have been more than 8 million children conceived through assisted reproductive technologies (ART) worldwide, and a significant proportion of them have reached puberty or young adulthood. Many studies have found that ART increases the risk of adverse perinatal outcomes, including preterm birth, low birth weight, small size for gestational age, perinatal mortality, and congenital anomalies. However, data regarding the long-term outcomes of ART offspring are limited. According to the developmental origins of health and disease theory, adverse environments during early life stages may induce adaptive changes and subsequently result in an increased risk of diseases in later life. Increasing evidence also suggests that ART offspring are predisposed to an increased risk of non-communicable diseases, such as malignancies, asthma, obesity, metabolic syndrome, diabetes, cardiovascular diseases, and neurodevelopmental and psychiatric disorders. In this review, we summarize the risks for long-term health in ART offspring, discuss the underlying mechanisms, including underlying parental infertility, epigenetic alterations, non-physiological hormone levels, and placental dysfunction, and propose potential strategies to optimize the management of ART and health care of parents and children to eliminate the associated risks. Further ongoing follow-up and research are warranted to determine the effects of ART on the long-term health of ART offspring in later life.

Neonatal outcomes in infants conceived using assisted reproductive technologies: A single medical center cohort study

BACKGROUND

A significant rise in the use of assisted reproductive technology (ART) has been observed, but concerns about its impact on neonatal outcomes have been considered. The aim of this retrospective cohort study is to determine the association between ART and the risk of neonatal complications and congenital anomalies within a recent time period.

METHODS

This retrospective study enrolled infants born after 20 weeks of gestation at a tertiary hospital in Taiwan between January 2019 and December 2021. The study population was divided into two groups: (1) ART pregnancy group and (2) natural pregnancy group. Maternal and neonatal characteristics, pregnancy complications, and neonatal outcomes were compared between the two groups. Multivariate logistic regression was used to adjust for maternal characteristics, preexisting maternal conditions, pregnancy complications, delivery methods, and infant characteristics.

RESULTS

This study enrolled 1770 infants comprising 289 in the ART pregnancy group and 1481 in the natural pregnancy group. The ART pregnancy group showed higher rates of multiple births, preterm births, low birth weights, and longer hospitalization periods. In the stratified analyses that were conducted on singleton births, no significant difference was observed. In the case of multiple births, lower rates of preterm birth, low birth weight, and respiratory support were observed in the ART pregnancy group. After adjusting for maternal and infant characteristics, ART was not considered a significant risk factor for adverse neonatal outcomes, including mortality, complications, and congenital anomalies.

CONCLUSION

Although ART pregnancies were more likely to result in multiple births and furthermore adverse outcomes, ART itself was not associated with an increased risk of poor neonatal outcomes. By implementing measures to control the number of implanted embryos, ensuring appropriate prenatal screening, and providing comprehensive postnatal care, the risks associated with increased multiple pregnancies caused by ART may be reduced.

Teratogenesis and the epigenetic programming of congenital defects: Why paternal exposures matter

Until recently, clinicians and researchers did not realize paternal exposures could impact child developmental outcomes. Indeed, although there is growing recognition that sperm carry a large amount of non-genomic information and that paternal stressors influence the health of the next generation, toxicologists are only now beginning to explore the role paternal exposures have in dysgenesis and the incidence of congenital malformations. In this commentary, I will briefly summarize the few studies describing congenital malformations resulting from preconception paternal stressors, argue for the theoretical expansion of teratogenic perspectives into the male preconception period, and discuss some of the challenges in this newly emerging branch of toxicology. I argue that we must consider gametes the same as any other malleable precursor cell type and recognize that environmentally-induced epigenetic changes acquired during the formation of the sperm and oocyte hold equal teratogenic potential as exposures during early development. Here, I propose the term epiteratogen to reference agents acting outside of pregnancy that, through epigenetic mechanisms, induce congenital malformations. Understanding the interactions between the environment, the essential epigenetic processes intrinsic to spermatogenesis, and their cumulative influences on embryo patterning is essential to addressing a significant blind spot in the field of developmental toxicology.

Lethality of Birth Defects in Live Born Infants Categorized by Gestational Age and Birth Weight

OBJECTIVE

This study aimed to describe lethality of birth defects (BDs) in newborns categorized by gestational age and birth weight and to identify BDs associated with prematurity.

STUDY DESIGN

Live born infants (n = 16,452) with isolated BDs classified by severity, and 42,511 healthy controls were assigned to categories: adequate growth, preterm, or small for gestational age (SGA). Proportion of cases and BDs' lethality rates were obtained by category and compared with controls.

RESULTS

Overall fewer malformed than nonmalformed infants were of adequate growth, while the opposite occurred in the preterm and SGA categories where gastroschisis and esophageal atresia were among the most outstanding defects. For most severe BDs, the early neonatal death rate was higher than control values in all categories; for mild defects, except cleft lip in the preterm category, they did not differ. Diaphragmatic hernia showed the highest lethality values, while those of spina bifida were among the lowest. Talipes, hypospadias, and septal heart defects were mild defects significantly associated with prematurity.

CONCLUSION

Although reasons, such as induced preterm delivery of fetuses with certain anomalies, could partially account for their high prematurity rates, susceptibility to preterm birth might exist through underlying mechanisms related with the defects. The identification of BDs associated with prematurity should serve to improve measures that prevent preterm birth especially of fetuses at risk.

KEY POINTS

· Some BDs predispose to prematurity.. · Prematurity is an additional risk factor for mortality in infants with mild defects.. · Lethality values should be adjusted by gestational age and birth weight..

Assisted reproductive technology (ART) and epigenetic modifications in the placenta

Assisted reproductive technology (ART) has become common amongst couples with infertility issues. ART is known to be successful, but epidemiological data indicates that ART is associated with placental disorders. Additionally, reports show increased risks of short- and long-term complications in children born to mothers undergoing ART. However, the mechanisms responsible for these events are obscure. The placenta is considered as a key organ for programming of diseases and ART procedures are suggested to alter the placental function and intrauterine growth trajectories. Epigenetic changes in maternal and foetal tissues are suggested to be the underlying mechanisms for these outcomes. Epigenetic regulation is known to evolve following fertilisation and before implantation and subsequently across gestation. During these critical periods of epigenetic 'programming', DNA methylation and chromatin remodelling influence the placental structure and function by regulating the expression of various genes. ART treatment coinciding with epigenetic 'programming' events during gametogenesis and early embryo development may alter the programming phases leading to long-term consequences. Thus, disruptions in placental development observed in ART pregnancies could be associated with altered epigenetic regulation of vital genes in the placenta. The review summarises available literature on the influence of ART procedures on epigenetic changes in the placenta.

Preconception paternal alcohol exposure decreases IVF embryo survival and pregnancy success rates in a mouse model

Increasingly, couples struggling with fertility turn to assisted reproductive techniques, including IVF, to have children. Despite the demonstrated influence of periconception male health and lifestyle choices on offspring development, studies examining IVF success rates and child health outcomes remain exclusively focused on maternal factors. Using a physiologically relevant mouse model, we tested the hypothesis that chronic paternal preconception alcohol intake adversely affects IVF success and negatively impacts IVF offspring fetoplacental growth. Using a voluntary, binge-like mouse model, we exposed sexually mature C57BL/6J males to three preconception treatments (0% (Control), 6% EtOH or 10% EtOH) for 6 weeks, isolated and cryopreserved caudal sperm from treated males, and then used these samples to fertilize oocytes before assessing IVF embryo developmental outcomes. We found that preconception paternal alcohol use reduced IVF embryo survival and pregnancy success rates in a dose-dependent manner, with the pregnancy success rate of the 10% EtOH treatment falling to half those of the Controls. Mechanistically, we found that preconception paternal alcohol exposure disrupts embryonic gene expression, including Fgf4 and Egfr, two critical regulators of trophectoderm stem cell growth and placental patterning, with lasting impacts on the histological organization of the late-term placenta. The changes in placental histoarchitecture were accompanied by altered regulation of pathways controlling mitochondrial function, oxidative phosphorylation and some imprinted genes. Our studies indicate that male alcohol use may significantly impede IVF success rates, increasing the couple's financial burden and emotional stress, and highlights the need to expand prepregnancy messaging to emphasize the reproductive dangers of alcohol use by both parents.

The use of IVF/ICSI and risk of postpartum hemorrhage: A retrospective cohort study of 153,765 women in China

Objective

Postpartum hemorrhage (PPH) is the leading cause of maternal morbidity and mortality. Identifying women who are at high risk of PPH is crucial for implementing early preventive and interventive strategies. This study aimed to examine whether there is an association between the use of in vitro fertilization (IVF) /intracytoplasmic sperm injection (ICSI) and increased risk of PPH.

Method

This retrospective cohort study was conducted using medical record data from women who delivered at a tertiary hospital in Shanghai, China, between January 1, 2013 and April 30, 2019. Logistic regression analysis was used to estimate the associations between the use of IVF/ICSI and the risk of PPH.

Results

A total of 153,765 pregnant women were included, of which 6,484 conceived through IVF/ICSI and147,281 conceived naturally. The incidence of PPH was 1.9% in this cohort. The incidence of PPH in women who conceived through IVF/ICSI was significantly higher than those in women who conceived naturally (3.4% vs. 1.7%, p < 0.01). The use of IVF/ICSI was associated with an increase in the amount of postpartum blood loss. Compared to women who conceived naturally, the average amount of postpartum blood loss increased by 42.1 mL (β = 42.1, 95% CI, 38.2-46.0) for women who conceived through IVF/ICSI. In addition, women who conceived through IVF/ICSI were at higher risk of maternal PPH. The adjusted odds ratio (OR) of PPH in women who conceived through ART was 2.7 (OR = 2.7, 95% CI, 2.3-3.1).

Conclusion

Our findings demonstrated that women who conceived through IVF/ICSI were at higher risk of PPH and suggested to obstetricians and midwives to identify and implement early preventative strategies for PPH among pregnant women who conceived through IVF/ICSI.

The Consequences of Assisted Reproduction Technologies on the Offspring Health Throughout Life: A Placental Contribution

The use of assisted reproductive technologies (ART) worldwide has led to the conception and birth of over eight million babies since being implemented in 1978. ART use is currently on the rise, given growing infertility and the increase in conception age among men and women in industrialized countries. Though obstetric and perinatal outcomes have improved over the years, pregnancies achieved by ART still bear increased risks for the mother and the unborn child. Moreover, given that the first generation of ART offspring is now only reaching their forties, the long-term effects of ART are currently unknown. This is important, as there is a wealth of data showing that life-long health can be predetermined by poor conditions during intrauterine development, including irregularities in the structure and functioning of the placenta. In the current review, we aim to summarize the latest available findings examining the effects of ART on the cardiometabolic, cognitive/neurodevelopmental, and behavioral outcomes in the perinatal period, childhood and adolescence/adulthood; and to examine placental intrinsic factors that may contribute to the developmental outcomes of ART offspring. Altogether, the latest knowledge about life outcomes beyond adolescence for those conceived by ART appears to suggest a better long-term outcome than previously predicted. There are also changes in placenta structure and functional capacity with ART. However, more work in this area is critically required, since the potential consequences of ART may still emerge as the offspring gets older. In addition, knowledge of the placenta may help to foresee and mitigate any adverse outcomes in the offspring.

Infertility treatment and the risk of small for gestational age births: a population-based study in the United States

Objective

To evaluate the association between infertility treatments and small for gestational age (SGA) births.

Design

Cross-sectional study.

Setting

United States, 2015–2019.

Patient(s)

Women (n = 16,836,228) who delivered nonmalformed, singleton live births (24–44 weeks’ gestation).

Intervention(s)

Any infertility treatment, including assisted reproductive technology (ART) and prescribed fertility-enhancing medications.

Main Outcome Measure(s)

Small for gestational age birth, defined as sex-specific birth weight <10% for gestational age. Associations between SGA and infertility treatment were derived from Poisson regression with robust variance. Risk ratios (RR) and 95% confidence intervals (CI) were derived after adjusting for confounders. In a sensitivity analysis, we corrected for nondifferential exposure misclassification and unmeasured confounding biases.

Result(s)

Subsequently, 1.4% (n = 231,177) of pregnancies resulted from infertility treatments (0.8% ART and 0.6% fertility-enhancing medications). Of these, SGA births occurred in 9.4% (n = 21,771) and 11.9% (n = 1,755,925) of pregnancies conceived with infertility treatment and naturally conceived pregnancies, respectively (adjusted RR, 1.07; 95% CI, 1.06, 1.08). However, after correction for misclassification bias and unmeasured confounding, infertility treatment was associated with a 27% reduced risk of SGA (bias-corrected RR, 0.73; 95% CI, 0.53, 0.85). Similar trends were seen for analyses stratified by exposure to ART and fertility-enhancing medications, as well as for SGA <5th and <3rd percentiles.

Conclusion(s)

Exposure to infertility treatment is associated with a reduced risk of SGA births. These findings, which are contrary to some published reports, may reflect changes in the modern practice of infertility care, maternal lifestyle, and compliance with prenatal care within the infertile population. Until these findings are corroborated, the associations must be cautiously interpreted.

In vitro fertilization causes excessive glycogen accumulation in mouse placenta

INTRODUCTION

Children conceived by assisted reproductive technologies have a high risk of suffering from obstetrical complications and long-term health problems, but the related mechanisms are not fully understood. Normal placental function is closely linked with foetal growth and future health. Given the significance of glycogen metabolism in placentas, we investigated the effect of in vitro fertilization (IVF) on glycogen storage in placentas using a mouse model.

METHODS

Mouse placentas were collected at E18.5 after natural mating or IVF, and the placental and foetal weights were recorded. The quantitative assay kit and histological staining were used to measure the glycogen content. Additionally, we detected the expression of multiple genes associated with glycogen synthesis/decomposition, glucose transporters, and the phosphorylation of Akt and Gsk3β.

RESULTS

Our findings showed that IVF resulted in a significantly increased mouse placental weight and enlarged junctional area. We found, compared to the control, excessive glycogen was accumulated in IVF placentas. However, we observed that multiple genes involved in glycogen generation (Gsk3b, Phka1, Phkb, Phkg1, and Phkg2) and glycogenolysis (Agl and Pygm) had lower mRNA levels in IVF placentas. Moreover, the expression levels of glycogen synthase, phosphorylase, Glut1, and Glut3 were significantly decreased in IVF placentas. The phosphorylation activities of Akt Ser473 and Gsk3β Ser9 were inhibited in IVF placentas.

DISCUSSION

IVF leads to enlarged mouse placentas with excessive glycogen storage in late pregnancy, and these abnormal changes may be associated with the activation of the Akt-Gsk3β pathway.

Cohort profile: the MUNICH Preterm and Term Clinical study (MUNICH-PreTCl), a neonatal birth cohort with focus on prenatal and postnatal determinants of infant and childhood morbidity

PURPOSE

The MUNICH Preterm and Term Clinical (MUNICH-PreTCl) birth cohort was established to uncover pathological processes contributing to infant/childhood morbidity and mortality. We collected comprehensive medical information of healthy and sick newborns and their families, together with infant blood samples for proteomic analysis. MUNICH-PreTCl aims to identify mechanism-based biomarkers in infant health and disease to deliver more precise diagnostic and predictive information for disease prevention. We particularly focused on risk factors for pregnancy complications, family history of genetically influenced health conditions such as diabetes and paediatric long-term health-all to be further monitored and correlated with proteomics data in the future.

PARTICIPANTS

Newborns and their parents were recruited from the Perinatal Center at the LMU University Hospital, Munich, between February 2017 and June 2019. Infants without congenital anomalies, delivered at 23-41 weeks of gestation, were eligible.

FINDINGS

Findings to date concern the clinical data and extensive personal patient information. A total of 662 infants were recruited, 44% were female (36% in preterm, 46% in term). 90% of approached families agreed to participate. Neonates were grouped according to gestational age: extremely preterm (<28 weeks, N=28), very preterm (28 to <32 weeks, N=36), late preterm (32 to <37 weeks, N=97) and term infants (>37+0 weeks, N=501). We collected over 450 data points per child-parent set, (family history, demographics, pregnancy, birth and daily follow-ups throughout hospitalisation) and 841 blood samples longitudinally. The completion rates for medical examinations and blood samples were 100% and 95% for the questionnaire.

FUTURE PLANS

The correlation of large clinical datasets with proteomic phenotypes, together with the use of medical registries, will enable future investigations aiming to decipher mechanisms of disorders in a systems biology perspective.

TRIAL REGISTRATION NUMBER

DRKS (00024189); Pre-results.

What are the causes for low birthweight in Japan? A single hospital-based study

Low-birthweight (LBW; <2,500 g) babies are at a higher risk of poor educational achievement, disability, and metabolic diseases than normal-birthweight babies in the future. However, reliable data on factors that contribute to LBW have not been considered previously. Therefore, we aimed to examine the distribution of the causes for LBW. A retrospective review of cases involving 4,224 babies whose mothers underwent perinatal care at Keio University Hospital between 2013 and 2019 was conducted. The LBW incidence was 24% (1,028 babies). Of the 1,028 LBW babies, 231 babies were from multiple pregnancies. Of the 797 singleton LBW babies, 518 (65%) were born preterm. Obstetric complications in women with preterm LBW babies included premature rupture of membrane or labor onset (31%), hypertensive disorders of pregnancy (HDP, 64%), fetal growth restriction (24%), non-reassuring fetal status (14%), and placental previa/vasa previa (8%). Of the 279 term LBW babies, 109 (39%) were small for gestational age. Multiple logistic regression analyses revealed the following factors as LBW risk factors in term neonates: low pre-pregnancy maternal weight, inadequate gestational weight gain, birth at 37 gestational weeks, HDP, anemia during pregnancy, female sex, and neonatal congenital anomalies. HDP was an LBW risk factor not only in preterm births but also in term births. Our results suggest that both modifiable and non-modifiable factors are causes for LBW. It may be appropriate to consider a heterogeneous rather than a simple classification of LBW and to evaluate future health risks based on contributing factors.

Single-blind clinical trial: Sperm selection based on capacity to pass through cumulus oophorous column improves ICSI outcomes

BACKGROUND

Sperm selection procedures for future strategies that aim to select normal spermatozoa with intact DNA to improve intracytoplasmic sperm injection (ICSI) outcomes are in early developing stage.

OBJECTIVES

The objective is to find out whether the sperm selection procedure based on the ability of spermatozoa to traverse the cumulus cells could improve clinical outcomes of ICSI technique in infertile couples with male factor etiology.

MATERIALS AND METHODS

For this single-blind clinical trial, mature metaphase II oocytes were retrieved from 150 couples with male factor infertility, male age lower than 45 years and female age under 38 years. These couples were divided into two groups. In control group (n = 75), spermatozoa processed by density gradient centrifugation (DGC) were used to inject the oocytes. In the study group (n = 75), the oocytes were divided into sibling groups. In one sibling group (DGC), the oocytes were inseminated with DGC-processed spermatozoa while in the other group (DGC-CC), they were inseminated with DGC-processed spermatozoa that passed cumulus oophorous column.

RESULTS

Mean fertilization and embryo quality were significantly higher in DGC-CC group compared to DGC and control group. In addition, mean of chemical pregnancy (52.27% vs. 34.14%; p = 0.05), clinical pregnancy based on sac (52.27% vs. 32.92%; p = 0.03), clinical pregnancy with heart beat (52.27% vs. 25.60%; p = 0.003) and ongoing pregnancy (43.18% vs. 21.95%; p = 0.02) rates were significantly higher in DGC-CC group compared to control group.

CONCLUSION

Sperm selection based on integrated systems such as DGC and ability to pass through cumulus oophorous column could improve clinical outcomes of ICSI in couples with male factor infertility.

Assisted reproductive technologies and the risk of congenital urogenital tract malformations: A systematic review and meta-analysis

A systematic review was conducted to evaluate the relationship between ART and the risk of urogenital tract malformations, especially hypospadias and cryptorchidism. Thirty-three papers were selected. Meta-analysis showed that ART was correlated with an increased risk of urogenital tract malformation in offspring (odds ratio (OR) = 1.61, 95% confidence interval (CI): 1.41-1.85), hypospadias (OR = 1.87, 95% CI: 1.47-2.40) and cryptorchidism (OR = 1.83, 95% CI: 1.54-2.18). Among offspring conceived by ART, multiple pregnancies appeared to result in a higher risk of urogenital tract malformation than singleton pregnancies (OR = 1.42, 95% CI: 0.99-2.04; P = 0.058). No significant difference in the risk of urogenital tract malformation was found between in vitro fertilization and intracytoplasmic sperm injection technologies. A sensitivity analysis showed that the above conclusions were relatively consistent. Conclusion: ART is correlated with an increased risk of urogenital tract malformations in offspring, especially hypospadias and cryptorchidism. Among ART offspring, multiple pregnancies may lead to a higher risk of urogenital tract malformations than singleton pregnancies, but more studies are needed for confirmation.

Perspective: One-Cell and Cleavage-Stage Mouse Embryos Thrive in Hyperosmotic Oviductal Fluid Through Expression of a Glycine Neurotransmitter Transporter and a Glycine-Gated Chloride Channel: Clinical and Transgenerational Implications

The osmolality of mouse oviductal fluid ranges from about 300 mOsmol/kg in the ampulla 0–3 h post coitus (h p.c.) to more than 350 mOsmol/kg in the isthmus 34–36 h p.c. Thus, it has been surprising to find that development of one-cell and cleavage-stage mouse embryos arrests in vitro in media exceeding 300 mOsmol/kg, and they develop best in unphysiological, hypotonic media. The glycine concentration in oviductal fluid can, however, rescue development in hypertonic media, so physiological conditions in vivo and in vitro likely work together to foster embryo well-being. Glycine acts on one-cell and cleavage-stage mouse embryos through the glycine-gated chloride channel, GLRA4, and uptake via the glycine neurotransmitter transporter, GLYT1. Since these processes lead to further signaling in neurons, the presence and function of such signaling in preimplantation embryos also should be investigated. The more we know about the interactions of physiological processes and conditions in vivo, the better we would be able to reproduce them in vitro. Such improvements in assisted reproductive technology (ART) could improve patient outcomes for IVF and potentially help prevent unwanted developmental abnormalities in early embryos, which might include undesirable epigenetic DNA and histone modifications. These epigenetic modifications may lead to transgenerational adult disorders such as metabolic syndrome and related conditions.