Could hormonal and follicular rearrangements explain timely menopause in unilaterally oophorectomized women?

STUDY QUESTION: Does unilateral oophorectomy modify the relationship between serum anti-Müllerian hormone (AMH) levels and antral follicle count (AFC)? SUMMARY ANSWER: No altered 'per-ovary' and 'per-follicle' AMH production and antral follicle distribution was evident in unilaterally oophorectomized women compared to matched controls. WHAT IS KNOWN ALREADY: The age of menopause onset is relatively unchanged in patients having undergone unilateral oophorectomy. Mechanisms that occur to preserve and maintain ovarian function in this context remain to be elucidated. STUDY DESIGN, SIZE, DURATION: Forty-one infertile women, with no polycystic ovary syndrome (PCOS) and no endometriosis, aged 19-42 years old, having undergone unilateral oophorectomy (One Ovary group; average time since surgery: 23.8 ± 2.2 months) were retrospectively age-matched (±1 year) with 205 infertile women having two intact ovaries and similar clinical features (Control group). PARTICIPANTS/MATERIALS, SETTING, METHODS: Serum AMH levels, 3-4 mm AFC, 5-12 mm AFC, and total AFC (3-12 mm) were assessed on cycle Day 3 in both groups. Hormonal and ultrasonographic measurements obtained from patients in the Control group (i.e. having two ovaries) were divided by two to be compared with measurements obtained from patients of the One Ovary group (i.e. having one single remaining ovary). To estimate per-follicle AMH production, we calculated the ratio between serum AMH levels over 3-4 mm AFC, 5-12 mm AFC, and total AFC (3-12 mm), and the strength of the correlation between serum AMH levels and total AFC. The main outcome measure was to assess Day 3 AMH/Day 3 AFC ratio and hormonal-follicular correlation. MAIN RESULTS AND THE ROLE OF CHANCE: As expected, before correction, mean serum AMH levels (1.46 ± 0.2 vs 2.77 ± 0.1 ng/ml, P < 0.001) and total AFC (7.3 ± 0.6 vs 15.1 ± 0.4 follicles, P < 0.0001) were lower in the One Ovary group compared to the Control group, respectively. Yet, after correction, per-ovary AMH levels (1.46 ± 0.2 vs 1.39 ± 0.1 ng/ml) and total AFC (7.3 ± 0.6 vs 7.5 ± 0.2 follicles) values were comparable between the two groups. Consistently, per-follicle AMH levels (3-4 mm, 5-12 mm, and total) were not significantly different between the two groups (0.39 ± 0.05 vs 0.37 ± 0.02 ng/ml/follicle; 0.69 ± 0.12 vs 0.59 ± 0.05 ng/ml/follicle, and 0.23 ± 0.03 vs 0.19 ± 0.01 ng/ml/follicle; respectively). In addition, the prevalence of 3-4 mm follicles was comparable between the two groups (66.7% for One Ovary group vs 58.8% for Control group, respectively). Finally, the correlation between serum AMH levels and total AFC was similar for patients in the One Ovary group (r = 0.70; P < 0.0001) compared to those in the Control group (r = 0.68; P < 0.0001). LIMITATIONS/REASONS FOR CAUTION: The retrospective character of the analysis might lead to potential bias. WIDER IMPLICATIONS OF THE FINDINGS: The present investigation did not provide evidence of altered 'per-ovary' and 'per-follicle' AMH production and antral follicle distribution in unilaterally oophorectomized women compared to matched controls. Further studies are warranted to support the hypothesis that follicle-sparing mechanisms are clearly at stake in remaining ovaries after unilateral oophorectomy to explain their long-lasting function and timely menopausal onset. STUDY FUNDING/COMPETING INTEREST(S): The authors have no funding or competing interests to declare. TRIAL REGISTRATION NUMBER: N/A.

[Impact of the type of incubator (non-humidified versus humidified) on embryo culture media osmolality]. / Impact du type d'incubateur (atmosphère humidifiée versus sec) sur l'osmolalité des milieux de culture embryonnaire.

INTRODUCTION: Benchtop incubators with small individual chambers have been developed in order to improve the stability of embryo culture conditions reducing the environmental stress during the embryo development. These new dry incubators were designed without any air humidification system in order to prevent bacterial proliferation and to enable the use of time-lapse system. However, an elevated evaporation of the culture media could occur in these conditions. The main objective of the study is to analyse the impact of the used incubator type on the embryo culture media osmolality. MATERIALS AND METHODS: Microdrops of 50µL of culture media were placed in 60mm diameter culture dishes, and quickly covered with either 7 or 8mL of mineral oil in an IVF workstation with laminar airflow. Two series of culture dishes have been randomly placed either in a humidified incubator or in a dry benchtop incubator. The microdrops of each culture dishes were sampled at D0, D1, D2, D3, and D5 respectively to measure the osmolality in triplicate using a cryoscopic osmometer. The mean values of osmolality in each incubator have been compared respectively on D0, D1, D2, D3 and D5 with appropriate statistical tests, and considered statistically significant when P<0.05. RESULTS: The osmolality of the microdrops placed in the dry benchtop incubator differed significantly after the third day of culture, regardless of the level of mineral oil in the culture dishes. Indeed, using Petri dishes covered respectively with 7 or 8mL of mineral oil, osmolality values of samples from the dry incubator were significantly higher than those from the humidified one, at D3 and D5 (D3/7mL: 273±2.1 vs. 268±1.0mOsm/kg; P=0.02; D3/8mL: 282±8.0 vs. 270±0.7mOsm/kg; P=0.04) and D5 (D5/7mL: 283±1.5 vs. 270±3.6mOsm/kg; P=0.004; D5/8mL: 287±5.6 vs. 268±2.3mOsm/kg; P=0.005). Furthermore, the analysis on paired samples showed that the osmolality in the dry benchtop incubator at D5 using 7mL of oil (283±1.5mOsm/kg; P=0.003) and at D3 (273±2.1mOsm/kg; P=0.016) and D5 (287±5.6mOsm/kg; P=0.009) using 8mL of oil was significantly higher than that measured at D0 (265±1.9mOsm/kg). CONCLUSION: A significant increase of the embryo culture media osmolality was observed in the dry benchtop incubator with ambient hygrometry in our standard conditions. Adding 1mL of oil was not sufficient to reduce the evaporation of the media. Although maintained at a physiological level, the impact of the osmolality changes on the in vitro embryo development has to be further determined.

Impact of oxygen tension according to embryo stage of development: a prospective randomized study.

Human embryo culture under 2-8% O2 is recommended by ESHRE revised guidelines for good practices in IVF labs. Nevertheless, notably due to the higher costs of embryo culture under hypoxia, some laboratories perform embryo culture under atmospheric O2 tension (around 20%). Furthermore, recent meta-analyses concluded with low evidence to a superiority of hypoxia on IVF/ICSI outcomes. Interestingly, a study on mice embryos suggested that oxidative stress (OS) might only have an adverse impact on embryos at cleavage stage. Hence, we aimed to demonstrate for the first time in human embryos that OS has a negative impact only at cleavage stage and that sequential culture conditions (5% O2 from Day 0 to Day 2/3, then «conventional¼ conditions at 20% O2 until blastocyst stage) might be a valuable option for human embryo culture. 773 IVF/ICSI cycles were included in this randomized clinical trial from January 2016 to April 2018. At Day 0 (D0), patients were randomized using a 1:2 allocation ratio between group A (20% O2; n = 265) and group B (5% O2; n = 508). Extended culture (EC) was performed when ≥ 5 Day 2-good-quality-embryos were available (n = 88 in group A (20% O2)). In subgroup B, 195 EC cycles were randomized again at Day 2 (using 1:1 ratio) into groups B' (5% O2 until Day 6 (n = 101)) or C (switch to 20% O2 from Day 2 to Day 6 (n = 94). Fertilization rate, cleavage-stage quality Day 2-top-quality-embryo (D2-TQE), blastocyst quality (Day 5-top-quality-blastocyst (D5-TQB) and implantation rate (IR) were compared between groups A and B (= cleavage-stage analysis), or A(20% O2), B'(5% O2) and C(5%-to-20% O2). Overall, characteristics were similar between groups A and B. Significantly higher rates of early-cleaved embryos, top-quality and good-quality embryos on Day 2 were obtained in group B compared to group A (P < 0.05). This association between oxygen tension and embryo quality at D2 was confirmed using an adjusted model (P < 0.05). Regarding blastocyst quality, culture under 20% O2 from Day 0 to Day 6 (group A) resulted in significantly lower Day 5-TQB number and rates (P < 0.05) compared to both groups B' and C. Furthermore, blastocyst quality was statistically equivalent between groups B' and C (P = 0.45). At Day 6, TQB numbers and rates were also significantly higher in groups B' and C compared to group A (P < 0.05). These results were confirmed analyzing adjusted mean differences for number of Day 5 and Day 6 top quality embryos obtained in group A when compared to those respectively in groups B' and C (P < 0.05). No difference in clinical outcomes following blastocyst transfers was observed. These results would encourage to systematically culture embryos under hypoxia at least during early development stages, since OS might be detrimental exclusively before embryonic genome activation.