Preimplantation Embryo Development - Essay Example

Student’s Name] [Instructor’s Name] [Course Title] [Date] PREIMPLANTATION EMBRYO DEVELOPMENT INTRODUCTION In this paper I aim to discuss in detail the various aspects of preimplanted embryo development. In the course of discussion I will cover a number of sub-topics that includes activation of embryonic genome (EGA/ZGA), Polarity, PED gene, Metabolism, Chromosome abnormalities, Growth factors, Paternal Factors, Imprinting, Apoptosis and new developments in ART that is assisted reproduction technology. In order to understand embryo development and how it can assist childless couples, it is imperative to comprehend how conception occurs in nature. In order for usual conception to happen, the male should ejaculate his semen, the liquid having the sperm, into the woman’s vagina close to the instant of ovulation, when the female’s ovary discharges an egg. EMBRYONIC DEVELOPMENT In humans the development of the embryo commences at fertilization that is the second week of gestation and carries on till the end of the tenth week of gestation which is also the eighth week of development. The zygote travels down the fallopian tube in the following few days. At the same time it also divides many times to create a ball of cells known as a morula. more cellular division is associated with the forming of a tiny cavity amongst the cells. This phase is known as the blastocyst (Boiso, 2002). Till this time there is no development in the overall structure of the embryo, as a result every division makes successively tinier cells. The blastocyst comes to the uterus around the 5th day after the fertilization. It is at this point that the lysis of the zona pellucida takes place which is a glycoprotein shell. This is needed so as to enable the trophectoderm cells of the blastocyst to come into connection with the luminal epithelial cells. It then stick to the uterine wall and becomes rooted in the endometrial cell layer (Boiso, 2002). This process is commonly known as implantation. In majority of the pregnancies, the conceptus implants almost eight to ten days after ovulation (Whelaon, 2000). The inner cell substance creates the embryo, whereas the cell layers to the outside form the membranes and placenta. GROWTH Quick growth takes place in the emryo which is governed by a variety of factors and as a result its external characteristics begin to take shape. This phase is known as differentiation, which creates the range of cell types example blood cells, kidney cells, and nerve cells. A sudden miscarriage or even abortion in the initial trimester of pregnancy is generally due to significant genetic mistakes or some abnormalities in the growing implanted embryo (Caranagh, 45-89). APOPTOSIS PCD-Programmed cell death is a very critical phase in both development of the embryo and homeostasis in senior tissues for the discharge of either infected, damaged or superfluous cells that takes place by activating an inbuilt suicide program. Apoptosis is one form of PCD and is derived from an ancient Greek term that was utilized to explain the phenomenon of "falling off" of certain petals from flowers. It was put forward by Kerr, Wyllie and Currie in 1972 to describe a strange kind of morphology of physiologically happening cell demise that exercises a modern but contradictory role to mitosis in the preimplanted embryo development (caranagh, 2000). Apoptosis in an implanted embryo is best described as by the maintenance of the solid cell membranes in the due course of the occuring suicide method and enables the neighbouring cells to enclose the dying cell to ensure that it does not discharge its contents and stimulate a local inflammatory process reaction. Cells that have been affected by apoptosis generally show a typical morphology that encompasses the fragmentation of the cell to a membrane bounded apoptotic structure, nuclear and cytoplasmic condensation. The endolytic opening of the DNA into a tiny oligonucleosomal division (Steller, 19). In a developing impanted embryo, apoptosis can be stimulated by any of the following actions. These include : 1. lineage production 2. any destruction caused because of the ionizing radiation or viral infection 3. extracellular trigger ACTIVATION OF EMBRYONIC GENOME(EGA/ZGA) The sdifference in the length of the cell series during the premature stages of embryo development can possibly be related to definite developmental actions that come about at this moment. Appearance of the embryonic genome has been observed during preimplantation embryo development. Proteins produced at dissimilar phases of embryogenesis were labeled as [35S]methionine and then alienated by one-dimensional clot electrophoresis. A chief alteration in the outline of protein synthesis has been practical amid the two- and the four-cell phases of embryonic growth. in addition the culture of embryos with an inhibitor of record (-amanitin) has exposed that the first amanitin receptive events capture place throughout the delayed two-cell stage. on the other hand, inhibition of record does not seize the embryo development up to the four-cell point. Taken jointly, the consequences point out that in humans the beginning of embryonic gene activation takes place at the delayed two-cell period. However, the initial two cleavage separations can happen in the nonattendance of transcription. METABOLISM The energy preferences that accompany the preimplantation embryo occurrence happen to be one of the most visible change. in the region of compaction, the human embryo switches from a reliance on the tricarboxylic acid series to a metabolism that is based on glycolysis. This striking change to glucose consumption as growth proceeds may be connected to a number of metabolic necessities: There is an augment in energy command in the region of the compaction, as protein amalgamation senlarge when the blastocoele is shaped. Glucose soffer the pentose moieties for nucleic acid synthesis and is necessary for non-essential amino acid biosynthesis. The embryo exhibits a substantial ability for anaerobic glycolysis by the blastocyst phase therefore it is imaginable that this leading the embryo for the anoxic situation it comes across at preimplantation. PATERNAL FACTOR AND PED GENE The recent developments suggest strongly the importance of the role of estrogens in males. It was noted that tamoxifen, a mock antiestrogen, when governed to grown-up males, in the prescribed amount range of 0.04-0.4 mg/kg per day, abridged fertility (Reubinoff B, Samueloff A, Ben-Haim M et al. 2002). The various researches and studies carried out also reveal that the drop in fruitfulness is not due to diminished fertilizing capability but for the reason that of the amplified pre-implantation embryo loss as apparent from an enlarge in number of unusual eggs in the treated set with no change in index of fertilization and it is also evident that in males and paternal factor is generally perceptive to tamoxifen as is implicated in embryogenesis. EMBRYO DEVELOPMENT AND CHROMOSOMAL ABNORMALITIES Recently formed chromosomal abnormalities are often discovered in preimplantation embryos created from stirred cycles (Reubinoff B, Samueloff A, Ben-Haim M et al. 2002). In count, occurrence of chromosomal trisomy is directly connected with amplified maternal age (Verlinsky and Kuliev, 69). It was testified that amongst all PGD cases presently performed globally, nearly 2/3rd cases are those deploying FISH to monitor embryonic aneuploidy for women with higher age (Simpson, 31). Embryonic chromosomal deviations are spawned from two kinds. First is non-disjunction that takes place during gamete meiosis and hence results in embryonic aneuploidy. The second is non-disjunction happening at some stage in zygote mitosis and leads to montage chromosomal abnormality. Aneuploidy viewing studies for oocytes and embryos in females in the age bracket of over 35 years proved that chromosome 13, 18 or 21 aberration in oocytes was as elevated as 43%; while the atypical rate of slashed embryos could reach 58%~66% (Wilton, 32). Also the rate of trisomy, monosomy and trisomy or monosomy were 30%, 12.5% and 5%, correspondingly. It is also associated with a elevated frequency of chromosomally atypical embryos, of which a few are able to build up to the blastocyst period. IVF plus PGD is an imperative footstep in the administration of infertile couples, but the practice has to shift towards a complete chromosome analysis. POLARITY The PAR proteins are present in all humans and they exercise a very vital role in maintaining cell polarity in a wide range of cell types. Asymmetric cell division is the main method that organisms utilize to produce cells with diverse properties. Asymmetric divisions happens during the whole stage of embryogenesis and futhermore carries on till adult life. Stem cells split asymmetrically, resulting in a daughter cell taking on a particular stem cell fate, and another daughter cell continues to replenish destructed or perfectly well cycling cells or tissues example skin. Some types of cancer occurs when the elements of the cell polarity mechanism turn defective. We know that inpreimplantation embryo since its aided reproduction the chnaces of cell polarity being altered and hence future risk is on the rise. IMPRITNING In the year 2003, 3 case studies were taken place and all reported an unpredictably high rate of Beckwith Wiedemann syndrome (BWS) in kids conceived with Preimplantation embryo. Patients with BWS include defects at chromosome 11p15 linked with organ overgrowth and also with abdominal wall imperfections as well as amplified risk of embryonic tumors (Gardner, 2001). These cases were suggestive of periodic cases of the ‘genetic imprinting’ chaos and also of Angelman Syndrome, that has also been connected with preimplantation embryos. Angelman Syndrome is described by stern mental retardation, movement defects, be deficient in speech and a glad temperament, and is related with a loss of utility of the motherly allele too (Gardner, 2001). Approximately 50 genes are differentially articulated depending on their source in either the egg cell or sperm cell. These ‘imprinted’ genes play vital functions in growth and expansion and in tumor repression. At the imprinted genes, just one allele is lively (that is either maternal or paternal) and the immobile allele is developmentally noticeable, by substance variation of the histone protein connected to DNA, or by adding up a methyl group (-CH3) to the bottom cytosine on the DNA, or mutually (Gardner, 2000). Premature in growth of the fetal germ cells in together both the sexes, the germ-cell genomes are removed of methylation characters that are present on the imprinted genes. At some stage in maturation of sperm and egg cell, on the other hand, remethylation of the imprinting alleles happens. DNA methylation, approximately perpetually related with suppression of transcription, aims one amongst the two parental alleles to calm it (Lizcano, 21-9). Following to fertilization, there are additional alterations in taken as a whole genomic methylation in definite cellular lineages of the embryo but significantly; imprinted alleles are confined from these impressions of demethylation and also of remethylation to uphold their appropriate dosage properties. As a result, most important epigenetic proceedings get during both germ-cell expansion and pre-implantation stage when ART actions are executed, perhaps prying with the accurate institution and upholding the embryo customs of genomic imprints (Lizcano, 21-9). PRENATAL DEVELOPMENT Prenatal development is the method through which implantation embryo or fetus happens to gestates in the course of pregnancy, that starts from fertilization and ends at birth. Usually, the phrase fetal development or embryology are replaced for each other in the same meaning. In humanbeings, following the end of embryogenesis around the tenth week of the gestational period, the remains of almost all the key organs of the human body have been formed. As a result after that stage, the coming fetal period, is charcterized both by organ, and very rigidly as chronologically too, by a series of vital happenings in weeks of gestational age (Lizcano, 2001). In preimplantation embryo since the natural course is altered hence the development and progress is slow and results in abnormalities later. ASSISTED REPRODUCTION TECHNOLOGY It would be impossible to write about the radical obstetric changes in pregnancies achieved through assisted reproduction procedures without explaining how, in such a short time, it has become possible to diagnose and treat successfully most of the factors that affect so many infertile couples. The birth of Louise Brown in 1978, achieved after many attempts with IVF and embryo transfer techniques, marked the beginning of rapid development in assisted reproduction techniques (Lizcano, 2001). These developments have been based on technological advances in endocrinological chemistry and instrumentation rather than in improving embryonic development in vitro. MODERN DAY ASSISTED REPRODUCTION TECHNIQUES To understand the achievements of assisted reproduction techniques it is first essential to define success. This is determined as the birth of a healthy baby after the use of any of the assisted reproduction techniques. Much has been achieved since 1978, all reflected by this definition of success. Tables 1a-1c show a summary of the evolution of pregnancies in various cycles of IVF-embryo transfer, reported in 37 by the Latin-American Network of Assisted Reproduction (Steptoe, 2001). The variability in the rate of clinical pregnancies and implantation is greater in centres that perform more than 100 cycles per year, compared with those performing fewer than 100 cycles. Data on the incidence of clinical pregnancies obtained after IVF, ICSI and other methods are shown in Table 1c. RECENT IMPROVEMENTS IN ASSISTED REPRODUCTION TECHNIQUES Improvements in the efficiency of ovulation induction have included the use of recombinant hormones, the daily monitoring of hormone concentrations and high-definition vaginal transducers. Surgical techniques include microlaparoscopy, and the development of new media and scientific and clinical equipment. It is highly debatable if these changes have raised the implantation rate per embryo much above that achieved in the pioneering work in Oldham. A misunderstanding arose over the purposes of IVF, in that many observers assumed it had been introduced to treat women with absent Fallopian tubes, or tubes that could not be repaired (Steptoe, 2001). Yet the reason why such patients were studied initially was because no-one would have believed that babies had been conceived in vitro if the mother had intact tubes! From the earliest days, Edwards had described the role of IVF in treating tubal disease, oligozoospermia, endometriosis, ovum donation, surrogacy and preimplantation genetic diagnosis on embryos. By now, all these indications are part of routine IVF. These studies have helped women as old as 62 to establish a pregnancy, which raises a larger problem about the menopause. Certain advances have led to greater efficiency in IVF. ICSI is the best example (Steptoe, 2001). The efficiency and purity of medications have also increased, facilitating the use of more efficient ovulation induction protocols. Research in andrology, embryology (gametes and embryos), and genetics has explained more clearly the processes of fertilization and segmentation. With ICSI, it is possible to introduce a spermatozoon into an oocyte. Spermatozoon can be obtained through masturbation, aspiration from the epididymis, or a direct biopsy of the testicle. These advances in ICSI have occurred in the past six years, demonstrating how fast technology can advance (Steptoe, 2000). In the embryo laboratory, new sequential culture media are being developed for the growth of embryos to advanced developmental stages. With prolonged development in vitro, only the best embryos survive, so they have higher overall implantation rates, per blastocyst, for example (Table 2). It may also be possible to identify the best embryos during their pronuclear or cleavage stages, to gain equally high implantation rates with these selected embryos (Gardner et al., 30). Today's results are far from ideal, which would be to use a single spermatozoon and a single oocyte, to generate an embryo with high implantation potential. By understanding where we stand in assisted reproduction techniques, it will be possible to understand the processes that are presently failing, and to identify specific causes of that failure in a later cycle (Gardner et al., 2000). THE PROBLEMS OF EARLY EMBRYONIC DEATH Most cases of embryonic death probably occur just before or after implantation. It is possible that similar causative factors are operational in natural and assisted reproductive cycles. IMPLANTATION AND ABORTION AFTER NATURAL CONCEPTION The main objective of assisted reproduction is to achieve the birth of a full-term baby, with full biophysical maturity. Yet those couples in need of reproductive techniques could well have a lower probability of implantation, despite the sophistication of the technologies used. The success of assisted reproduction techniques must be compared with the natural reproductive efficiency of humans to distinguish between couples considered fertile or infertile (Table 3). In the general population, a woman has a 15-20% chance of pregnancy during a single ovulatory cycle. After one year, 90% of women can become pregnant, and 95% by the end of the second year. This leaves 5-10% of the patients who are unable to get pregnant. The onset of pregnancy does not guarantee a live baby at the end of gestation, because many fetuses will succumb. This form of natural selection occurs in 15-20% of all pregnancies. Until recently it was not possible to differentiate the infertile couple from those who had lost their fetus prematurely (Steptoe, 517). The only resources available were the external examination of a pregnant woman's abdomen, and confirmation of fetal heartbeat using Pinar's stethoscope. Today, laboratory tests evaluate the baby's development and establish its well-being. With this information, a series of indications and treatments can help embryos to complete their development, or the pregnancy can be terminated either vaginally or abdominally (Conde Agudela and Kafury, 99; Bahado Singh and Oz, 19). Fetal loss after natural conception is greatest during the first 12 weeks of gestation, and this loss in the general population varies between 20 and 25%. In general, abortion has been defined as the termination of a pregnancy before week 20, or of a product that weighs less than 500 g; however, this definition does not reflect the human reproductive situation. Many early pregnancies can now be detected that were not evident before (Steptoe, 426). Equipment should be available to obtain such data and to allow the clinician to prescribe the required treatment for the pregnant woman. EARLY PREGNANCY AND EARLY EMBRYONIC LOSS AFTER ASSISTED CONCEPTION Some very early pregnancies are associated with a consecutive increase in chorionic gonadotrophin, but the gestational sac cannot be seen with ultrasound before the onset of the menstrual period. This is called biochemical pregnancy, as it can only be detected through laboratory tests. New tests such as enzyme-linked immunosorbent assay (ELISA) can demonstrate and quantify new embryo markers that are secreted in the early stages of development, such as early pregnancy factor which is synthesized 48 h after fertilization. This compound can be detected in the woman's peripheral blood so it is a valuable early marker for pregnancy (Caranagh, 2000). Detecting such early forms of embryonic loss differentiates women who produce good embryos that fail to implant from those that implant but soon die. The former patient is considered to be fertile, whereas the latter is considered to have habitual abortions, with different aetiologies and different treatments. With assisted reproduction techniques we can answer many questions that before 1978 were impossible to solve. These include knowing that the egg is fertilized by spermatozoa from the husband, whether cleavage of the embryo occurs, if embryonic development to blastocyst is normal, and whether the blastocyst can initiate a pregnancy inside the uterus. Almost all of these questions already have a physiological answer, which helps us to understand the natural reproduction process in humans, and these answers clarify the causes of infertility. Nevertheless, many embryos are transferred to the uterus, yet only 10-15% of them end up as a full-term baby (Stern,2000, 250-6). Clearly, many embryos that were selected morphologically as normal are unable to develop to full term. Several of the causes of early embryonic loss have been identified. It is possible using fluorescence in-situ hybridization (FISH) to ascertain if an embryo carries a chromosomal disorder before it is transferred. There could be a hormonal problem, quite independent of the hormones known at present because, in assisted reproduction, most centres provide routine hormonal support either vaginally or muscularly. There may be a problem with the endometrium (Stern, 250-6). Problems that have been identified include a poor subendometrial blood flow at the site of implantation, which prevents adequate perfusion of the embryos. WORKS CITED Abramov Y, Elchalal U, Shenker G 2003 Obstetric outcome of in vitro fertilized pregnancies complicated by severe ovarian hyperstimulation syndrome: a multicenter study. Fertility and Sterility 70, 1070-1075. Asch RH, Ellsworth LR, Balmaceda JP et al. 2004 Pregnancy after translaparoscopic gamete intrafallopian transfer, Lancet 2, 1034. Asch RH, Verez JR, Asch B et al. 2001 Spontaneous post-implantation embryo resolution: a new concept in embryo loss. Middle East Fertility Society Journal 3, 43-46. Bahado Singh R, Oz AD 2001 New Down Syndrome screening algorithm. Ultrasound biometry and multiple serum markers combined with maternal age. American Journal of Obstetrics and Gynecology 179, 1627-1631. Blanchette H 2003 Obstetric performance of patients after oocyte donation. American Journal of Obstetrics and Gynecology 168, 1803-1809. Boiso I, Veiga A, Edwards RG 2002 Fundamentals of human embryonic growth in vitro and the selection of high-quality embryos for transfer. Reproductive BioMedicine Online 5, in press. Caranagh A 2002 An update of the early pregnancy factor and its role in early pregnancy. Assisted Reproduction and Genetics 14, 495-496. Conde Agudela A, Kafury G (2005) Triple marker test as a screening of Down Syndrome. A meta-analysis. Obstetrical and Gynecological Surveys 54, 144-155. Dhont M 2002 Perinatal outcome of pregnancies after assisted reproduction. A case control study. Journal of Assisted Reproduction and Genetics 14, 575-580. Dias Pereira G, Hajenius PJ, Mol BWJ et al. 2003 Fertility outcome after systemic methotrexate and laparoscopic salpingostomy for tubal pregnancy. Lancet 353, 724-725. Edwards RG 2001 Test tubes babies. Nature 293, 253-256. Elsner C, Tucker M, Sweitzer C et al. 2003 Multiple pregnancy rate and embryo number transferred during in vitro fertilization. American Journal of Obstetrics and Gynecology 177, 350-355. Gardner DK, Schoolcraft WB, Wagley I et al. 2001 A prospective randomized trial of blastocyst culture and transfer in vitro fertilization. Human Reproduction 13, 3434-3440. Gardner DK, Lane M, Stevens J et al. 2000 Blastocyst score affects implantation and pregnancy outcome: towards a single blastocyst tranfer. Fertility and Sterility 71, 1055-1058. Jones HR Jr, Jones GS, Andrews MC et al. 2002 The program of in vitro fertilization at Norfolk. Fertility and Sterility 38, 14-21. Lizcano Gil LA, Lucena C, Lucena E 2001 Methods in preimplantation diagnosis. Reproductive BioMedicine Online 2, 20--31. Maman E, Lunenfeld E, Levy A et al. 2001 Obstetric outcome of singleton pregnancies conceived by in vitro fertilization and ovulation induction compared with those conceived spontaneously. Fertility and Sterility 70, 240-245. Piccinni MP, Romagnani S 2004 Regulation of fetal allograft survival by hormone-controlled Th1- and Th2-type cytokines. Immunologic Research 15, 141-150. Reubinoff B, Samueloff A, Ben-Haim M et al. 2002 Is the obstetric outcome of in vitro fertilized singleton gestations different from natural ones? A controlled study. Fertility and Sterility 67, 1077-1083. Society of Assisted Reproduction Techniques Registry (SART) 2000 Assisted Reproductive Technology in United States: 2000 Results generated from the American Society for Reproductive Medicine. Steptoe PC, Edwards RG 1976 Reimplantation of a human embryo with subsequent tubal pregnancy. Lancet 1, 880. Steptoe PC, Edwards RG 2001 Birth after reimplantation of a human embryo. Lancet 2, 366. Stern JJ, Coulam CB 2002 Mechanism of recurrent spontaneous abortion I. Ultrasound Findings. American Journal of Obstetrics and Gynecology 166, 1844-1850. Stern J, Dorfman AD, Gutierrez-Najar AJ et al. 2006 Frequency of abnormal karyotypes among abortuses from women with and without history of recurrent spontaneous abortion. Fertility and Sterility 65, 250-253. Stovall T 2003 Single dose methotrexate an expanded clinical trial. American Journal of Obstetrics and Gynecology 168, 1759-1765. Trusell J, Wilson C 2005 Population Studies 269-286. Whelan J 2000 The ovarian hyperstimulation syndrome. Fertility and Sterility 73, 883-896. Zegers-Hothschild F, MacKenna A, Fernandez E, Sepulveda MS 2001 Results of assisted reproduction techqniques in Latin America. Reproductive BioMedicine Online 2, 129-137. APPENDIX TABLE 1A. CLINICAL PREGNANCIES AFTER IVF. Legend for Chart: A - Cycles initiated B - No. of centres C - Pregnancy rate (%) A B C 0-49 37 40 50-99 28 40 100-199 8 42 200-499 3 40 TABLE 1B. ONGOING PREGNANCIES AND BIRTHS ESTABLISHED AFTER ASSISTED REPRODUCTION (1996-1998). Legend for Chart: B - 'Las Condes' C - Clinic AGN A B C Ectopic 7 17 Abortions up to 19 weeks 48 18 Abortions 19 weeks 3 4 Full-term pregnancies 323 177 20-27 weeks 6 28-35 weeks 83 43 36-40 weeks 226 128 Total 381 393 AGN = Grupo de Reproducción y Genética AGN y Asociados. TABLE 1C. CLINICAL PREGNANCIES ACCORDING TO THE PROCEDURE AND MATERNAL AGE. DATA FROM REGISTRO LATINOAMERICANO DE REPRODUCCION ASSISTIDA, 1997. Legend for Chart: A - Maternal age (years) B - IVF n C - % D - GIFT n E - % F - Other n G - % A B C D E F G 40 68 10 5 21 2 28 GIFT = gamete intra-Fallopian transfer. Number of cycles: total = 4676; IVF = 3817; GIFT = 161; other 37; unclassified = 661. TABLE 2. PREGNANCY AND TWINNING RATE IN RELATION TO THE QUALITY AND NUMBER OF BLASTOCYSTS TRANSFERRED (FROM GARDNER, 2000). Legend for Chart: A - Variable B - Blastocyst quality Good n = >1 C - Good n = 1 D - Poor A B C D Pregnant 59 16 7 patients (n) Implantation 69.9 50 28.1 rate (%) Clinical pregnancy 86.8 69.6 43.8 rate (%) No. of twins (%) 36 (61) 8 (50) 2 (28) TABLE 3. HUMAN REPRODUCTIVE EFFICACY (FROM TRUSELL AND WILSON, 1985). Legend for Chart: A - Months B - Monthly probability C - Accumulated probability A B C 1 0.2 0.20 2 0.2 0.36 3 0.2 0.49 4 0.2 0.59 5 0.2 0.67 6 0.2 0.74 7 0.2 0.79 8 0.2 0.83 9 0.2 0.86 10 0.2 0.89 11 0.2 0.91 12 0.2 0.93 TABLE 4. FINAL OUTCOMES (N) OF MULTIPLE PREGANCIES (FROM ASCH ET AL., 1998). Legend for Chart: A - Originally B - No. of cases C - Singleton D - Twin E - Triplet F - Quadruplet A B C D E F Singleton 414 294 NA NA NA Twin 132 40 79 NA NA Triplet 48 6 11 27 NA Quadruplet 19 2 9 4 2 Quintuplet 7 1 3 2 0 NA = not applicable. TABLE 5. SPONTANEOUS POST-IMPLANTATION EMBRYO LOSS (FROM ASCH ET AL., 1998). Legend for Chart: B - Original gestational sacs (n) C - Lost gestational sacs (n) D - Spontaneous loss (%) A B C D Singleton 414 120 29 Twin 264 66 25 Triplet 144 35 24 Quadruplet 76 34 45 Quintuplets 35 19 54 Total 933 274 29 TABLE 6. KARYOTYPIC ABNORMALITIES IN HUMAN ABORTIONS (FROM STERN, 1996). Legend for Chart: A - Chromosome analysis B - Recurrent abortions C - No recurrent abortions A B C Normal 40 56 Abnormal 54 74 Aneuploidy 45 61 Polyploidy 9 13 Total analysed 94 130 TABLE 7. DEVELOPMENTAL AGE AT TERM AND PREMATURITY INCIDENCE IN SINGLETONS, TWINS AND TRIPLETS. Legend for Chart: A - Type of gestation B - Term (weeks) C - Incidence of prematurity (%) A B C Singleton 40 5-7 Twins 37 40-50 Triplets 34-35 80-85 Quadruplets 29-30 100 TABLE 8. FETAL ANOMALIES IN ALL IVF PROCEDURES (1996-1998). DATA FROM REGISTRO LATINOAMERICANO DE REPRODUCCIÓN ASISTIDA, 1998. Legend for Chart: A - Procedure B - 1996 Newborn C - 1996 Fetal anomalies (%) D - 1997 Newborn E - 1997 Fetal anomalies (%) F - 1998 Newborn G - 1998 Fetal anomalies (%) H - Total (%) A B C D E F G H IVF 777 0.5 662 0.5 385 1.0 0.6 GIFT 142 1.4 36 5.6 1 ND 2.8 Others 0 ND 0 ND 1 ND ND IVF Cryo 54 0.0 33 3.0 13 ND 1.0 ICSI 532 0.8 504 1.4 296 3.0 1.5 SUZI 9 0.0 7 0.0 0 ND ND AH 43 0.0 0 ND 12 0.0 ND OD 154 1.3 101 3.0 99 2.0 2.0 Total 1711 0.7 1343 1.2 807 2.0 1.1 IVF = in-vitro fertilization; GIFT = gamete intra-Fallopian transfer; Cryo = cryopreservation; ICSI = intracytoplasmic sperm injection; SUZI = subzonal insemination; AH = assisted hatching; OD = oocyte donation; ND = no data. TABLE 9. PREMATURITY RATES (FROM THE REGISTRO LATINOAMERICANO DE REPRODUCTION ASISTIDA, 1997). Legend for Chart: A - Gestational order B - Prematurity Read More