P–755 Perinatal outcomes following Day–4 embryo transfer compared to Day–2, Day–3 and Day–5 embryo transfer: an analysis of 56,346 singleton live births

Study question

Are perinatal outcomes of singleton live births following Day–4 embryo transfer (ET) different to Day–2, Day–3 and Day–5 ET?

Summary answer

Perinatal outcomes of singleton live births following Day–4 ET are similar with those following Day–2, Day–3 and Day–5 ET.

What is known already

The morula represents a critical stage in preimplantation embryo development, but the usage of morula transfer on Day–4 has received little attention. Recent work from our group suggested that live birth rates following Day–4 ET appear higher than cleavage-stage ET, but lower than blastocyst ET. Therefore, Day–4 appears an alternative day to perform ET, offering the benefits of extended culture for embryo selection, but with shorter in-vitro culture exposure, as well as improving flexibility and planning in the IVF Clinic. However, there are extremely limited data available on the perinatal outcomes after Day–4 ET compared to cleavage-stage and blastocyst ET.

Study design, size, duration

Retrospective cohort study using data from the anonymised dataset of the Human Fertilisation and Embryology Authority (HFEA) in the UK between 2000 and 2016. Data from singleton live births of women undergoing their first IVF/ICSI cycle were analysed to compare perinatal outcomes after fresh Day–2,3,4,5 embryo transfers.

Participants/materials, setting, methods

Births resulting from the first, fresh, autologous, stimulated, non-PGT cycles, with full data, were included. After exclusions, a total 56,346 singleton live births were included in the analysis (17,613 from Day–2 ET, 15,533 from Day–3 ET, 508 from Day–4, 22,692 from Day–5 ET).

Binary/multinomial logistic regression analysis was performed to adjust for important cofounders. Adjusted odds ratios (aORs) and 95% confidence intervals (95%CI) were calculated. The level of significance was set at < 0.05.

Main results and the role of chance

The probabilities of birth at full-term (FT) and normal birthweight (NBW) after Day–4 transfer (FT 90.4%; NBW 84.6%) were similar to Day–2 (FT 89.7%, aOR 0.994, [0.734–1.344]; NBW 81.9%, aOR 0.881, [0.708–1.096]), Day–3 (FT 90.2%, aOR 1.026, [0.760–1.386]; NBW 82.4%, aOR 0.894, [0.719–1.111]) and Day–5 transfer (FT 90.4%, aOR 1.001, [0.743–1.350]; NBW 83.7%, aOR 0.920, [0.741–1.142]).

The probabilities of preterm birth (PTB) and very preterm birth (VPTB) after Day–4 transfer (PTB 9.3%; VPTB 0.4%) were similar to Day–2 (PTB 9.5%; aOR=0.952; VPTB 0.8%; aOR=2.172), Day–3 (PTB 9.0%, aOR=0.920; VPTB 0.9%, aOR=2.174), and Day–5 transfer (PTB 8.8%; aOR=0.955; VPTB 0.8%, aOR=1.956).

The probabilities of very-low birthweight (VLBW), low birthweight (LBW), high birthweight (HBW) and very-high birthweight (VHBW) after Day–4 transfer (VLBW 0.9%, LBW 7.9%, HBW 6.3%, VHBW 0.3%) were similar to Day–2 (VLBW 1.8%, aOR=1.827; LBW 8.0%, aOR=1.015; HBW 8.1%, aOR=1.174; VHBW 0.2%, aOR=0.590), Day–3 (VLBW 1.8%, aOR=1.788; LBW 7.4%, aOR=0.927; HBW 8.3%, aOR=1.256; VHBW 0.2%, aOR=0.503) and Day–5 transfer (VLBW 1.6%, aOR=1.782; LBW 6.9%, aOR=0.894; HBW 7.5%, aOR=1.215; VHBW 0.2%, aOR=0.796).

The probability of having a female baby after Day–4 transfer (51.6%) was similar to Day–2 (49.2%, aOR 0.940), Day–3 (49.3%, aOR 0.931) and Day–5 transfer (48.3%, aOR 0.869).

Limitations, reasons for caution

The study is limited by its retrospective nature, the inability to adjust for additional confounders and the small number of singleton births after Day–4 ET. It is not known how Day–4 ET was decided. The incidence of congenital abnormalities was not analysed due to incomplete registration in the dataset.

Wider implications of the findings: Perinatal outcomes of singleton live births following Day–4 ET are similar with those following Day–2, Day–3 and Day–5 ET, suggesting that morula transfer is equally safe as cleavage-stage and blastocyst transfer. Data on a larger number of live births from well-designed RCTs are required to confirm these findings.

Trial registration number

Not applicable

Maternal periconceptional and first trimester protein restriction in beef heifers: effects on placental parameters and fetal and neonatal calf development

Few studies have investigated the effects of nutrition during the periconception and early gestation periods on fetal and placental development in cattle. In this study, nulliparous yearling heifers (n=360) were individually fed a diet high or low in protein (HPeri and LPeri) beginning 60 days before conception. From 24 to 98 days after conception, half of each treatment group was changed to the alternative high- or low-protein diet (HPost and LPost) yielding four groups in a 2×2 factorial design. A subset of heifers (n=46) was necropsied at 98 days after conception and fetoplacental development assessed. Placentome number and volume decreased in response to LPeri and LPost diets respectively. Absolute lung, pancreas, septum and ventricle weights decreased in LPost versus HPost fetuses, whereas the post-conception diet altered absolute and relative liver and brain weights depending on sex. Similarly, changes in fetal hepatic gene expression of factors regulating growth, glucose output and lipid metabolism were induced by protein restriction in a sex-specific manner. At term, neonatal calf and placental measures were not different. Protein restriction of heifers during the periconception and early gestation periods alters fetoplacental development and hepatic gene expression. These changes may contribute to functional consequences for progeny, but this may not be apparent from gross morphometry at birth.

The Effects of Developmental Programming upon Neonatal Mortality

The greatest loss in ruminant production systems occurs during the neonatal period. The maternal environment (nutrition and physiologic status) influences neonatal mortality and morbidity as it reportedly affects (a) Dystocia, both via increasing birth weight and placental dysfunction; (b) Neonatal thermoregulation, both via altering the amount of brown adipose tissue and its ability to function via effects upon the hypothalamic-pituitary-thyroid axis; (c) Modification of the developing immune system and its symbiotic nutrient sources; (d) Modification of maternal and neonatal behavior.

Subacute ruminal acidosis reduces sperm quality in beef bulls

Breeding bulls are commonly fed high-energy diets, which may induce subacute ruminal acidosis (SARA). In this experiment, 8 Santa Gertrudis bulls (age 20 ± 6 mo) were used to evaluate the extent and duration of effects of SARA on semen quality and the associated changes in circulating hormones and metabolites. The bulls were relocated and fed in yards with unrestricted access to hay and daily individual concentrate feeding for 125 d before SARA challenge. Semen was collected and assessed at 14-d intervals before the challenge to ensure acclimatization and the attainment of a stable spermiogram. The challenge treatments consisted of either a single oral dose of oligofructose (OFF; 6.5 g/kg BW) or an equivalent sham dose of water (Control). Locomotion, behavior, respiratory rate, and cardiovascular and gastrointestinal function were intensively monitored during the 24-h challenge period. Rumen fluid samples were retained for VFA, ammonia, and lactate analysis. After the challenge, semen was then collected every third day for a period of 7 wk and then once weekly until 12 wk, with associated blood collection for FSH, testosterone, inhibin, and cortisol assay. Percent normal sperm decreased in bulls dosed with OFF after the challenge period ( < 0.05) and continued to remain lower on completion of the study at 88 d after challenge. There was a corresponding increase in sperm defects commencing from 16 d after challenge. These included proximal cytoplasmic droplets ( < 0.001), distal reflex midpieces ( = 0.01), and vacuole and teratoid heads ( < 0.001). Changes in semen quality after challenge were associated with lower serum testosterone ( < 0.001) and FSH ( < 0.05). Serum cortisol in OFF bulls tended to be greater ( = 0.07) at 7 d after challenge. This study shows that SARA challenge causes a reduction in sperm quality sufficient to preclude bulls from sale as single sire breeding animals 3 mo after the event occurred.

Maternal endocrine adaptation throughout pregnancy to nutrient manipulation: consequences for sexually dimorphic programming of thyroid hormones and development of their progeny

Maternal nutrient restriction during critical windows of fetal development alters postnatal growth, often in a sexually dimorphic manner. Intrauterine growth restriction is frequently characterized by accelerated growth and increased adiposity in later life. Thyroid hormones are implicated as part of the mechanism involved in this scenario via their actions within the hypothalamic-pituitary-thyroid axis. We fed high (H = 240%) and low (L = 70%) levels of recommended daily crude protein intake during the first and second trimesters of gestation to beef heifers to investigate effects to their progeny's plasma concentrations of free and total triiodothyronine (FT3 and TT3) and thyroxine (FT4 and TT4) from birth until weaning at 191 days of age (n = 68). The study design was a two-by-two factorial. For male progeny, exposure to maternal diets low in protein during the first trimester of gestation resulted in greater FT4 at birth (P < 0.05) which was subsequent to lower concentrations of leptin in maternal plasma at 271 days of gestation compared with their high-protein-exposed counterparts. These same animals went on to have greater milk intake during the latter half of the lactation period (P < 0.05) and exhibited faster rates of average daily gain (ADG) relative to birth weight during this time (P < 0.05). For all progeny, independent of sex, exposure to low-protein maternal diets during the second trimester of gestation resulted in greater FT3 relative to TT3 at birth. Because FT3 at birth and 29 days was positively associated with ADG (P < 0.05) and ADG relative to birth weight (P < 0.05), it is proposed that FT3 plays an integral role in catch-up growth in the bovine as per other species. Protein intake during the first and second trimesters of gestation has a sexually dimorphic effect on progeny plasma thyroid hormone concentrations, and these changes are associated with altered milk intake and postnatal growth pathway.

Restoration of ovarian function and natural fertility following the cryopreservation and autotransplantation of whole adult sheep ovaries

STUDY QUESTION

Is it possible to restore ovarian function and natural fertility following the cryopreservation and autotransplantation of whole ovaries, complete with vascular pedicle, in adult females from a large monovulatory animal model species (i.e. sheep)?

SUMMARY ANSWER

Full (100%) restoration of acute ovarian function and high rates of natural fertility (pregnancy rate 64%; live birth rate 29%), with multiple live births, were obtained following whole ovary cryopreservation and autotransplantation (WOCP&TP) of adult sheep ovaries utilizing optimized cryopreservation and post-operative anti-coagulant regimes.

WHAT IS KNOWN ALREADY

Fertility preservation by WOCP&TP requires successful cryopreservation of both the ovary and its vascular supply. Previous work has indicated detrimental effects of WOCP&TP on the ovarian follicle population. Recent experiments suggest that these deleterious effects can be attributed to an acute loss of vascular patency due to clot formation induced by damage to ovarian arterial endothelial cells.

STUDY DESIGN, SIZE, DURATION

Study 1 (2010–2011; N = 16) examined the effect of post-thaw perfusion of survival factors (angiogenic, antioxidant, anti-apoptotic; n = 7–8) and treatment with aspirin (pre-operative versus pre- and post-operative (n = 7–9)) on the restoration of ovarian function for 3 months after WOCP&TP. Study 2 (2011–2012; N = 16) examined the effect of cryoprotectant (CPA) perfusion time (10 versus 60 min; n = 16) and pre- and post-operative treatment with aspirin in combination with enoxaparine (Clexane^®; n = 8) or eptifibatide (Integrilin^®; n = 8) on ovarian function and fertility 11–23 months after WOCP&TP.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Both studies utilized mature, parous, Greyface ewes aged 3–6 years and weighing 50–75 kg. Restoration of ovarian function was monitored by bi-weekly blood sampling and display of behavioural oestrus. Blood samples were assayed for gonadotrophins, progesterone, anti-Müllerian Hormone and inhibin A. Fertility restoration in Study 2 was quantified by pregnancy rate after a 3 month fertile mating period and was confirmed by ultrasound, hormonal monitoring and live birth. Ovarian function was assessed at sacrifice by ovarian appearance and vascular patency (Doppler ultrasound) and by follicular histology.

MAIN RESULTS AND THE ROLE OF CHANCE

In Study 1, survival factors were found to have no benefit, but the inclusion of pre-operative aspirin resulted in four ewes showing acute restoration of ovarian function within 3 weeks and a further six ewes showing partial restoration. The addition of post-operative aspirin alone had no clear benefit. In Study 2, combination of aspirin with additional post-operative anti-coagulants resulted in total acute restoration of ovarian function in 14/14 ewes within 3 weeks of WOCP&TP, with 9/14 ewes becoming pregnant and 4/14 giving birth to a total of seven normal lambs. There was no difference between anti-coagulants in terms of restoration of reproductive function and fertility. In contrast, the duration of CPA perfusion was highly significant with a 60 min perfusion resulting in ovaries of normal appearance and function with high rates of primordial follicle survival (70%) and an abundant blood supply, whereas ovaries perfused for 10 min had either resorbed completely and were vestigial (7/14) or were markedly smaller (P < 0.01). It is concluded that both the degree of CPA penetration and the maintenance of post-operative vascular patency are critical determinants of the success of WOCP&TP.

LIMITATIONS, REASONS FOR CAUTION

Before application of this technology to fertility preservation patients, it will be critical to optimize the CPA perfusion time for different sized human ovaries, determine the optimum period and level of anti-coagulant therapy, and confirm the normality of offspring derived from this procedure.

WIDER IMPLICATIONS OF THE FINDINGS

This technology holds promise for the preservation of fertility in women. It could also potentially be applied to the cryopreservation of other reproductive or even major organs (kidneys) where there are considerable difficulties in storing donated tissue.

STUDY FUNDING/COMPETING INTEREST(S)

Funding was received from the Medical Research Council, University of Nottingham. The authors confirm that they have no conflict of interest in relation to this work.