Articles

A recent case report of sex-discordant monochorionic twins has challenged the notion that monochorionic twins are definitely monozygotic. This phenomenon may be explained by a postulated third type of twinning, referred to as sesquizygosity. Unlike monozygotic and dizygotic cases, the underlying mechanisms of this rare event are less extensively defined. However, triploidy or the presence of three pronuclei is thought to explain sesquizygosity. The proposed mechanisms of triploid embryo formation explaining sesquizygotic twinning are discussed, considering the relevance and incidence of triploid embryos in IVF.

Twinning is a complex phenomena occurring at 1.25% of spontaneous pregnancies, while its incidence in IVF cases rises up to 25%. Three types of twins can be defined according to its zigosity: if they originate from one fertilised egg, monozygotic, if they come from two eggs fertilised by two different sperm, dizygotic, or a postulated intermediate of these events defined as sesquizygotic. Here, the characteristics and main causes of monozygotic and dizygotic twinning will be explained. Also, reasons for the increased frequency of twins in IVF will be provided.

FF components vary under hormonal regulation and may also be affected by pathologies, environmental conditions, stress or contaminants. The study and analysis of FF parameters can be used to distinguish the best oocytes, to develop personalised treatments or to improve gamete culture conditions.

Figure 1. Biopsy of a human embryo. The holding pipette on the left abuts the zona pellucida of the embryo. The biopsy pipette on the right is inside the opening in the zona pellucida. One cell is inside the pipette (1). ​​INTRODUCTION The importance of aneuploidy screening in assisted reproduction has gained popularity since the introduction of preimplantation genetic testing (PGT) at the beginning of the 1990s (2). PGT for aneuploidies screening (PGT-A) is recommended for couples experiencing recurrent pregnancy…

Figure 1. Solid Surface Vitrification (A) and slow cooling equipment (B) (1). THE HISTORY OF SPERM CRYOPRESERVATION Human semen cryopreservation has a long history that begins at the end of the nineteenth century. After prior observations on sperm surviving cooling at very low temperatures (-150º C) (2), Mantegazza (1866) first suggested the idea of human sperm banks (3). Years later, Mantegazza proved it was possible to extend human sperm lifespan up to four days by cooling at moderate sub-zero temperatures…

Figure 1. (A) Embryo displaying multi-/micronucleation in both blastomeres; (B) Embryo with binucleation in one of the blastomeres. Arrows point to the position of multiple nuclei (1). INTRODUCTION Selection of high-quality embryos is an important factor for the successful outcome of assisted reproduction technologies (ART). Nowadays, criteria for selection are mainly based on morphological features such as embryo fragmentation, cell number, blastomeres uniformity, etc. (2). The parameters studied so far have been demonstrated to be useful indicators of embryo quality. Their…

This technique, first proposed in 1980 by Evenson and coauthors (23), uses flow cytometry to measure sperm DNA integrity. It tests the vulnerability of DNA to acid-induced denaturation by exposure to acridine orange media (AO) (24). AO binds to both double-stranded and single-stranded DNA, but fluoresces in different colour, being red or green, respectively.

Figure 1. Artificial shrinkage of blastocoelic cavity in human expanded blastocysts by hyperosmotic sucrose solutions, before and after the treatment (1). One of the main factors related to embryo selection for transfer is the extension of embryo culture up to blastocyst stage. This approach has been demonstrated to improve clinical outcomes after in vitro fertilization IVF (2). Consequently, in the last couple decades a specific blastocyst grading system has been applied to assess embryo morphology during blastocyst stage (appearance of the inner cell…

Fertilization  involves  the fusion of male and female gametes. However, for this to occur both cells must undergo certain morphological and physiological changes in order to be able to fuse. The sperm cell must undergo a process known as capacitation, which implies a series of changes regarding motility and plasma membrane composition (among others), essential to acquire the ability to fertilize.

Figure 1. Human blastocysts (10). The main goal of in vitro fertilization (IVF) is the birth of a single healthy child. However, the consequences and the effects of assisted reproductive techniques on children’s short- and long-term health have always been a source of discussion. Although IVF techniques and protocols have dramatically improved, the overall success rates are still relatively low, and assisted reproduction units still face the challenge of improving pregnancy rates (1). For this purpose, transfer of a single human embryo at…

Figure 1. Mouse embryo culture from 2-cell stage to blastocyst using KSOM medium (1). INTRODUCTION WHY IS IT IMPORTANT TO TALK ABOUT IVF CULTURE MEDIA? Within the last 40 years, the improvement of assisted reproduction technologies (ART) has experienced rapid and great advances (2). This success is largely due to the important enhancement of the culture conditions, specially IVF media (2,3), since this is where the early embryo develops up to blastocyst stage (Figure 1) before being transferred into the womb. However,…

Figure 1. Illustration showing evidences of endometriosis found in specific locations of the female reproductive organs [1]. Endometriosis is defined as the presence of endometrial tissue outside the uterus, which induces a chronic inflammatory reaction. It is generally assumed that lesions arise through retrograde endometrial tissue loss during menstruation, coelomic metaplasia and lymphatic spread in immunologically and genetically susceptible individuals. Associated symptoms usually have an impact on the general physical, mental and social well-being (2,3,4). ​ This condition is found…

Figure 1. Pre-ovulation human ovary. http://www.glowm.com/section_view/heading/Clinical%20Anatomy%20of% 20the%20Uterus,%20Fallopian%20Tubes,%20and%20Ovaries/item/1 INTRODUCTION Cryopreservation is a basic procedure in the daily work with assisted reproduction techniques. It is routinely and successfully applied to sperm samples, spare embryos from in vitro fertilization (IVF) cycles and oocytes. In the past, slow freezing procedures were carried out with no reliable clinical outcomes, especially in egg freezing programs. After the recent introduction of vitrification it is now possible to cryopreserve embryos and oocytes, and to assure patients that this…

  Figure. 1. Schematic overlapping view of the follicular and luteal phases of the ovary with their corresponding predominant steroid profiles and the proliferative and secretory phases of the endometrium cycle. Modified from (1) INTRODUCTION The menstrual cycle in humans lasts 28 days in regular terms, being the first day of menses considered the first day of the cycle. But in actuality, cycle refers to a series of intermingled events mainly related to three aspects: the ovary, the uterus (or…

Figure 1. Blastocyst. Modified from https://i.ytimg.com/vi/dvTXEGcNFZg/sddefault.jpg INTRODUCTION WHAT IS CRYOPRESERVATION? The first successful in vitro fertilization (IVF) treatment was in 1978. Since that, there have been a remarkable number of advances in assisted reproductive technologies (ART). Initially, all available embryos were transferred in IVF treatments owing to its low success rate. However, improvements on clinical and laboratory aspects led not only to increased pregnancy rates, but also to increased risk of multiple pregnancies. To prevent this, fewer embryos are transferred…

Figure 1. Aniline blue-stained human sperm bound to a surface coated with hyaluronic acid. Modified form [1]. See Sperm selection for fertilization (I). INTRODUCTION In assisted laboratories, semen samples are usually obtained after masturbation and the ejaculate is collected into a container. However, semen recovered from non-spermicidal condoms can be of higher quality because of the time producing the sample influences in the amount of seminal emission before ejaculation (2). Moreover, according to the World Health Organization criteria, laboratory manual…

Figure 1. Close micrograph of a segment of the mid-piece of a mammalian spermatozoon, showing the helicoidally disposed of mitochondria. (A) Cross section. (B) The surface of the plasma membrane. [modified from (1)]. INTRODUCTION Fertility treatments are more and more common in our days, reason why it is important to perform these procedures accurately resembling in vivo conditions. Additionally, the male factor may oftentimes be underrated, and yet it is 50% of the treatment. The following text aims to establish…

Figure 1. Day 3 embryo biopsy (1) Assisted reproduction technology (ART) can help fertile couples to achieve successful pregnancies. Sometimes, reproductive desires of these couples are affected by the presence of a genetic disease in either partner. In such cases, couples are at a reproductive risk and find themselves in the need of assistance that only ART can provide. Preimplantation genetic diagnosis (PGD) provides an alternative to prenatal diagnosis to detect the specific genetic condition or disease they suffer from,…