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.

Despite the high level of standardization of the intracytoplasmic sperm injection (ICSI) technique, there are some aspects that deserve special attention and should still be improved. The major drawback of the technique is its invasiveness, as during cytoplasmic aspiration different structures of the oocyte may be lost or damaged. This is partly because the microtools used in ICSI were not specially designed for assisted reproduction but for other medical–biological disciplines. In view of the above caveats, the aim of the study was to compare the results of ICSI with the traditional oocyte-holding pipette and the oocyte-holding pipette without aspiration (PiWA). In total, 155 patients and 1037 oocytes were included in the study. In each ICSI cycle, half of the oocytes were microinjected using a traditional holding pipette and the other half using a PiWA. In result, the PiWA technique produced a significant increase in the fertilization rate: 88.12% (95%CI: 84.62–90.92%); holding pipette: 73.33% (95%CI: 68.72–77.49%). Also, it produced a significant decrease in the embryo degeneration rate compared with the traditional holding pipette [PiWA: 2.07% (95%CI: 1.11–3.8%); holding pipette: 4.51% (95%CI: 3.06–6.59%)]. Pregnancy rate depended on the holding technique used, both in single embryo transfers (n = 59; χ2 = 4.608; P-value = 0.032) and double embryo transfers (n = 156; χ2 = 4.344; P-value = 0.037); with PiWA presenting a significantly higher pregnancy rate than the traditional holding technique. Based on current evidence and the present results, improvements should focus on decreasing the invasiveness of the microinjection itself by minimizing or avoiding aspiration and cytoplasmic disorganization, as is successfully achieved with PiWA.

Fertilization failure (FF) and zygotic arrest after ICSI have a huge effect on both patients and clinicians, but both problems are usually unexpected and cannot be properly diagnosed. Fortunately, in recent years, gene sequencing has allowed the identification of multiple genetic variants underlying failed ICSI outcomes, but the use of this approach is still far from routine in the fertility clinic. In this systematic review, the genetic variants associated with FF, abnormal fertilization and/or zygotic arrest after ICSI are compiled and analyzed. Forty-seven studies were included. Data from 141 patients carrying 121 genetic variants affecting 16 genes were recorded and analyzed. In total, 27 variants in PLCZ1 (in 50 men) and 26 variants in WEE2 (in 24 women) are two of the factors related to oocyte activation failure that could explain a high percentage of male-related and female-related FF. Additional variants identified were reported in WBP2NL, ACTL9, ACTLA7, and DNAH17 (in men), and TUBB8, PATL2, TLE6, PADI6, TRIP13, BGT4, NLRP5, NLRP7, CDC20 and ZAR1 (in women). Most of these variants are pathogenic or potentially pathogenic (89/121, 72.9%), as demonstrated by experimental and/or in silico approaches. Most individuals carried bi-allelic variants (89/141, 63.1%), but pathogenic variants in heterozygosity have been identified for PLCZ1 and TUBB8. Clinical treatment options for affected individuals, such as chemical-assisted oocyte activation (AOA) or PLCZ1 cRNA injection in the oocyte, are still experimental. In conclusion, a genetic study of known pathogenic variants may help in diagnosing recurrent FF and zygotic arrest and guide patient counselling and future research perspectives.

We present a commentary on the article published in the Zygote FirstView: ‘Importance of real-time measurement of sperm head morphology in intracytoplasmic sperm injection’ by Fumiaki Itoi and colleagues. We comment on the importance of providing the microscope setup details whenever sperm morphology visualization is discussed. The claim of ×6000–10,000 magnification is misleading as such levels of magnification are impossible to achieve.

The role of hyaluronic acid (HA) as a ‘physiologic selector’ is also well recognized in vitro: it has been demonstrated that spermatozoa that bind to immobilized HA in vitro are those having completed their plasma membrane remodelling, and cytoplasmic and meiotic maturation. Sperm selection using HA has been expected to increase the implantation rate in intracytoplasmic sperm injection (ICSI) cycles. This work was designed to evaluate an alternative product for slowing sperm motility that contains HA and measures its outcomes: fertilization rate, embryo quality, and implantation and pregnancy rates. The present study found a positive drift in embryo quality that was statistically significant in the study group (SpermSlow™-ICSI) with teratozoospermia compared with PVP-ICSI in the same group. There were differences in the pregnancy rate (statistically insignificant in normozoospermia, asthenozoospermia, oligozoospermia, and teratozoospermia) in the SpermSlow-ICSI group compared with PVP-ICSI. The HA-ICSI technique in assisted reproduction technology (ART) is an important way to improve fertilization rate, embryo quality, and pregnancy rate.

In the treatment of infertile patients with non-obstructive azoospermia (NOA) caused by the deletion of the azoospermia factor c region (AZFc) on the Y chromosome, synchronous and asynchronous surgical strategies are discussed. Clinical data from NOA patients with the AZFc deletion who underwent micro-TESE were analyzed retrospectively. The sperm retrieval rate (SRR) and sperm utilization rate of synchronous and asynchronous operation groups were followed up and compared. The fertilization rate, high-quality embryo rate, clinical pregnancy rate, abortion rate, and cumulative live birth rate of ICSI in patients with successful sperm retrieval were compared between the two groups. The two groups had sperm utilization rates of 98.9% (93/94) and 50.0% (14/28), respectively. The asynchronous group’s sperm consumption rates were much lower than those of the synchronous operation group. Fertilization rate, high-quality embryo rate, clinical pregnancy rate of fresh transfer cycle, abortion rate, and cumulative live birth rate of patients in the synchronous operation group with fresh sperm, and the asynchronous operation group with thawed sperm, respectively, were 30.6% vs 33.8%, 33.8% vs 40.7%, 40.0% vs 12.5%, 30.4% vs 7.1%. Between the two groups, there was no significant difference. This suggests that individuals with NOA caused by the AZFc deletion have a high possibility of successfully acquiring sperm using micro-TESE and ICSI to conceive their own offspring. Synchronous micro-TESE is recommended to improve sperm utilization rate and the cumulative live birth rate.

The follicle-stimulating hormone (FSH) and its receptor regulate the quantity and quality of spermatozoa production. Several studies have analyzed the effect of single nucleotide polymorphisms (SNPs) in exon 10 of the FSH receptor (FSHR) on basic semen parameters without yet reaching a firm consensus. The aim of this study was to evaluate the effect of p.Thr307Ala and p.Asn680Ser polymorphisms in exon 10 of the FSHR gene, in infertile men, on intracytoplasmic sperm injection (ICSI) outcomes. This study was conducted between March 2019 and February 2020 on infertile couples undergoing ICSI at Al Hadi Laboratory and Medical Center, Lebanon. Couples with severe infertility factors that may impair gametogenesis/embryogenesis (e.g. advanced maternal age, premature ovarian failure, underwent gonadotoxic treatments, etc.) were excluded from the study. Semen and blood samples were collected from infertile men on the day of oocyte collection. Infertile men (n = 173) were screened for FSHR variants using polymerase chain reaction-restriction fragment length polymorphism. Moreover, fertilization rates, embryo quality, and pregnancy outcomes were evaluated. Higher sperm concentrations were found in the p.Thr307Ala group than the p.Thr307Thr (P < 0.01) and p.Ala307Ala (P < 0.05) groups. Furthermore, fertilization rate was significantly lower in the p.Ala307Ala genotype than in the p.Thr307Thr genotype (P < 0.05). We showed that FSHR variants in infertile men undergoing ICSI could affect sperm concentration, motility, and fertilization rates. Therefore, it will be important to confirm these results in further studies using a larger sample size.