Increased risk of large-for-gestational age birthweight in singleton siblings conceived with in vitro fertilization in frozen versus fresh cycles

Preterm Birth and Small Size for Gestational Age in Singleton, In Vitro Fertilization Births Using Donor Oocytes

We used 2006-2015 US National Assisted Reproductive Technology Surveillance System data to compare preterm birth and fetal growth for liveborn singletons (24-42 weeks' gestation) following in vitro fertilization with donor versus autologous oocytes. Using binary and multinomial logistic regression, we computed adjusted odds ratios and 95% confidence intervals for associations between use of donor oocytes and preterm delivery, being small for gestational age (SGA), and being large for gestational age (LGA), stratified by fresh and thawed embryo status and accounting for maternal characteristics and year of birth. There were 204,855 singleton births from fresh embryo transfers and 106,077 from thawed embryo transfers. Among fresh embryo transfers, donor oocyte births had higher odds of being preterm (adjusted odd ratio (aOR) = 1.32, 95% confidence interval (CI): 1.27, 1.38) or LGA (aOR = 1.27, 95% CI: 1.21, 1.33) but lower odds of being SGA (aOR = 0.81, 95% CI: 0.77, 0.85). Among thawed embryo transfers, donor oocyte births had higher odds of being preterm (aOR = 1.57, 95% CI: 1.48, 1.65) or SGA (aOR = 1.22, 95% CI: 1.14, 1.31) but lower odds of being LGA (aOR = 0.87, 95% CI: 0.82, 0.92). Use of donor oocytes was associated with increased odds of preterm delivery irrespective of embryo status; odds of being SGA were increased for donor versus autologous oocyte births among thawed embryo transfers only.

Effect of embryo and blastocyst transfer on the birthweight of live-born singletons from FET cycles

PURPOSE

To evaluate the effect of culture duration (embryo (day 3) transfer vs. blastocyst (day 5-6) transfer) on the birthweight of singletons from frozen embryo transfer (FET) cycles.

METHODS

A total of 1092 singletons were analyzed in this retrospective study. The distribution of large for gestational age (LGA) infants, the mean birthweight, and z scores of singletons were compared between the day 3 and day 5-6 transfer groups. Multiple linear regression analysis was performed to evaluate the relationships between confounding factors and singleton birthweight.

RESULTS

The proportion of LGA infants significantly increased with BMI (BMI < 20, 12.8%; 20 ≤ BMI ≤ 25, 23.2%; BMI > 25, 32.3%; P < 0.0001). However, the proportions of small for gestational age (SGA) and LGA infants were not significantly different between day 3 and day 5-6 transfers. The absolute mean birthweight of singletons was not significantly different between day 3 transfer (3422 ± 547 g) and day 5-6 transfer (3433 ± 559 g; P = 0.732). The z scores (calculated from a reference population) of singletons were also not significantly different between the two groups (0.499 vs. 0.533, P = 0.625). Multiple linear regression analysis showed that maternal BMI, gestational age, and infant gender had significant effects on singleton birthweight, while culture duration (P = 0.731) did not significantly affect singleton birthweight.

CONCLUSIONS

In vitro culture duration did not affect the birthweight of newborns resulting from day 3 to day 5-6 transfers in FET cycles.

Fresh versus frozen embryo transfer for full-term singleton birth: a retrospective cohort study

Background

Improvements in vitrification and frozen embryo transfer (FET) technologies have rapidly increased, and some evidence suggests that FET may increase pregnancy rates and lead to more favourable perinatal outcomes. However, the outcome of interest should be offspring safety. Therefore, the primary objective of our study was to investigate whether FET was preferable to fresh embryo transfer (ET) in terms of full-term neonatal birthweight and congenital malformations.

Methods

This was a retrospective cohort study of patients with no pregnancy-related complications who underwent first fresh ETs (n = 2059) or FETs (n = 2053), resulting in full-term singletons births. Outcome measures were neonatal birthweight, low birthweight (LBW), small-for-gestational age (SGA), large-for-gestational age (LGA), macrosomia and congenital malformations. Additionally, we used logistic regression to adjust for baseline characteristics (age, BMI, No. of embryos transferred and embryo stage) between the two groups.

Results

The mean neonatal birthweight was higher for singletons born after FET than for singletons born after fresh ET (3468.7 ± 475.3 vs. 3386.7 ± 448.1; p < 0.001). The frequencies of full-term singleton LBW and SGA after FET were significantly lower than those after fresh ET (1.7% vs. 3.0 and 4.4% vs. 6.7%, respectively), with adjusted rate ratios of 0.59 (95% CI, 0.37 to 0.98; p = 0.026) and 0.73 (95% CI, 0.55 to 0.99; p = 0.041), respectively. FET resulted in higher frequencies of macrosomia and LGA (15.1% vs 10.2 and 22.8% vs. 17.5%, respectively) than fresh ET, with adjusted rate ratios of 1.43 (95% CI, 1.16 to 1.75; p = 0.001) and 1.26 (95% CI, 1.07 to 1.49; p = 0.007), respectively. Furthermore, the incidence of congenital malformations was not different between the two groups (1.2% vs. 0.9%), with a rate ratio of 0.288.

Conclusions

After the cycles with pregnancy-related complications were excluded and after adjustments for baseline characteristics, women undergoing FET were associated with a higher neonatal birthweight than women undergoing fresh ET cycles. Additionally, the FET protocol was associated with lower rates of LBW and SGA and higher rates of macrosomia and LGA than the fresh ET protocol. Meanwhile, no difference in the congenital malformation rate was evident between the two groups.

[Birth weight and frozen embryo transfer: State of the art]

The aim of this study was to update our acknowledgment if there is a link between assisted embryo cryopreservation and epigenetics in human? Animal studies have demonstrated epigenetics consequence and especially imprinting disorders due to in vitro culture. In human, it is important to note that after frozen embryo transfer birth weight is significantly increased by 81 to 250g. But these studies cannot identify the reasons of such difference. This review strongly suggests that embryo cryopreservation is responsible for birth weight variations but mechanisms not yet elucidated. Epigenetics is probably one of these but to date, none study is able to prove it. We have to be attentive on a possible link between assisted reproductive technology (ART) and epigenetics reprogrammation.

Effect of frozen/thawed embryo transfer on birthweight, macrosomia, and low birthweight rates in US singleton infants

BACKGROUND

Singleton infants conceived using assisted reproductive technology have lower average birthweights than naturally conceived infants and are more likely to be born low birthweight (<2500 gr). Lower birthweights are associated with increased infant and child mortality and poor adult health outcomes, including cardiovascular disease, hypertension, and diabetes. Data from registry and single-center studies suggest that frozen/thawed embryo transfer may be associated with larger birthweights. To date, however, a nationwide, full-population study on United States infants born using frozen/thawed embryo transfer has not been reported.

OBJECTIVES

The objective of this study was to compare the effect of frozen/thawed vs fresh embryo transfer on birthweight outcomes for singleton, term infants conceived using in vitro fertilization in the United States between 2007 and 2014, including average birthweight and the risks of both macrosomia (>4000 g) and low birthweight (<2500 g).

STUDY DESIGN

We used data from the Centers for Disease Control and Prevention's National Assisted Reproductive Technology Surveillance System to compare birthweight outcomes of live-born singleton, autologous oocyte, term (37-43 weeks) infants. Generalized linear models for all infants and stratified by infant sex were used to assess the relationship between frozen/thawed embryo transfer and birthweight, in grams. Infertility diagnosis, year of treatment, maternal age, maternal obstetric history, maternal and paternal race, and infant gestational age and sex were included in the models. Missing race data were imputed. The adjusted relative risks for macrosomia and low birthweight were evaluated using multivariable predicted marginal proportions from logistic regression models.

RESULTS

In total, 180,184 singleton, term infants were included, with 55,898 (31.02%) having been conceived from frozen/thawed embryos. Frozen/thawed embryo transfer was associated with, on average, a 142 g increase in birthweight compared with infants born after fresh embryo transfer (P < .001). An interaction between infant sex and embryo transfer type was significant (P < .0001), with frozen/thawed embryo transfer having a larger effect on male infants by 16 g. The adjusted risk of a macrosomic infant was 1.70 times higher (95% confidence interval, 1.64-1.76) following frozen/thawed embryo transfer than fresh embryo transfer. However, adjusted risk of low birthweight following frozen/thawed embryo transfer was 0.52 (95% confidence interval, 0.48-0.56) compared with fresh embryo transfer.

CONCLUSION

Frozen/thawed embryo transfer, in comparison with fresh embryo transfer, was associated with increased average birthweight in singleton, autologous oocytes, term infants born in the United States, with a significant interaction between frozen/thawed embryo transfer and infant sex. The risk of macrosomia following frozen/thawed embryo transfer was greater than that following fresh embryo transfer, but the risk of low birthweight among frozen/thawed embryo transfer infants was significantly decreased in comparison with fresh embryo transfer infants.

First trimester pregnancy ultrasound findings as a function of method of conception in an infertile population

PURPOSE

The aim of this study was to determine whether first trimester ultrasound measurements of crown rump length (CRL) and gestational sac diameter (GSD) differ depending on the method of conception among infertile women.

METHOD

Infertile women, ages 21-50 years old, who conceived viable, singleton pregnancies via fresh embryo transfer (ET), frozen ET, non-in vitro fertilization (IVF) fertility treatment, or spontaneously were included in this observational cohort study at an academic fertility practice. Embryonic growth trajectories defined by the CRL and GSD at 6 and 8 weeks' gestation were analyzed and compared among the methods of conception.

RESULTS

Crown rump length at 6 weeks' gestation was smaller for conceptions achieved via fresh ET compared with frozen ET in a natural cycle (1.50 vs. 2.50 mm, p = 0.017). Crown rump length was smaller at 8 weeks' gestation in conceptions achieved via fresh ET compared to frozen ET in a programmed cycle (16.13 vs. 17.02 mm, p = 0.039).

CONCLUSION

Among infertile women, embryo growth may differ between fresh and frozen ET as early as 6 and 8 weeks' gestation.

Pregnancy and birth outcomes in couples with infertility with and without assisted reproductive technology: with an emphasis on US population-based studies

Infertility, defined as the inability to conceive within 1 year of unprotected intercourse, affects an estimated 80 million individuals worldwide, or 10-15% of couples of reproductive age. Assisted reproductive technology includes all infertility treatments to achieve conception; in vitro fertilization is the process by which an oocyte is fertilized by semen outside the body; non-in vitro fertilization assisted reproductive technology treatments include ovulation induction, artificial insemination, and intrauterine insemination. Use of assisted reproductive technology has risen steadily in the United States during the past 2 decades due to several reasons, including childbearing at older maternal ages and increasing insurance coverage. The number of in vitro fertilization cycles in the United States has nearly doubled from 2000 through 2013 and currently 1.7% of all live births in the United States are the result of this technology. Since the birth of the first child from in vitro fertilization >35 years ago, >5 million babies have been born from in vitro fertilization, half within the past 6 years. It is estimated that 1% of singletons, 19% of twins, and 25% of triplet or higher multiples are due to in vitro fertilization, and 4%, 21%, and 52%, respectively, are due to non-in vitro fertilization assisted reproductive technology. Higher plurality at birth results in a >10-fold increase in the risks for prematurity and low birthweight in twins vs singletons (adjusted odds ratio, 11.84; 95% confidence interval, 10.56-13.27 and adjusted odds ratio, 10.68; 95% confidence interval, 9.45-12.08, respectively). The use of donor oocytes is associated with increased risks for pregnancy-induced hypertension (adjusted odds ratio, 1.43; 95% confidence interval, 1.14-1.78) and prematurity (adjusted odds ratio, 1.43; 95% confidence interval, 1.11-1.83). The use of thawed embryos is associated with higher risks for pregnancy-induced hypertension (adjusted odds ratio, 1.30; 95% confidence interval, 1.08-1.57) and large-for-gestation birthweight (adjusted odds ratio, 1.74; 95% confidence interval, 1.45-2.08). Among singletons, in vitro fertilization is associated with increased risk of severe maternal morbidity compared with fertile deliveries (vaginal: adjusted odds ratio, 2.27; 95% confidence interval, 1.78-2.88; cesarean: adjusted odds ratio, 1.67; 95% confidence interval, 1.40-1.98, respectively) and subfertile deliveries (vaginal: adjusted odds ratio, 1.97; 95% confidence interval, 1.30-3.00; cesarean: adjusted odds ratio, 1.75; 95% confidence interval, 1.30-2.35, respectively). Among twins, cesarean in vitro fertilization deliveries have significantly greater severe maternal morbidity compared to cesarean fertile deliveries (adjusted odds ratio, 1.48; 95% confidence interval, 1.14-1.93). Subfertility, with or without in vitro fertilization or non-in vitro fertilization infertility treatments to achieve a pregnancy, is associated with increased risks of adverse maternal and perinatal outcomes. The major risk from in vitro fertilization treatments of multiple births (and the associated excess of perinatal morbidity) has been reduced over time, with fewer and better-quality embryos being transferred.

Impact of the IVF laboratory environment on human preimplantation embryo phenotype

The phenotype of the human embryo conceived through in vitro fertilization (IVF), that is its morphology, developmental kinetics, physiology and metabolism, can be affected by numerous components of the laboratory and embryo culture system (which comprise the laboratory environment). The culture media formulation is important in determining embryo phenotype, but this exists within a culture system that includes oxygen, temperature, pH and whether an embryo is cultured individually or in a group, all of which can influence embryo development. Significantly, exposure of an embryo to one suboptimal component of the culture system of laboratory typically predisposes the embryo to become more vulnerable to a second stressor, as has been well documented for atmospheric oxygen and individual culture, as well as for oxygen and ammonium. Furthermore, the inherent viability of the human embryo is derived from the quality of the gametes from which it is created. Patient age, aetiology, genetics, lifestyle (as well as ovarian stimulation in women) are all known to affect the developmental potential of gametes and hence the embryo. Thus, as well as considering the impact of the IVF laboratory environment, one needs to be aware of the status of the infertile couple, as this impacts how their gametes and embryos will respond to an in vitro environment. Although far from straight forward, analysing the interactions that exist between the human embryo and its environment will facilitate the creation of more effective and safer treatments for the infertile couple.