**5. Preimplantation genetic diagnosis (PGD)**

Preimplantation genetic diagnosis is a multistep procedure that analyzes the genetic material from a single or several cells, with the purpose to avoid a pregnancy affected by a specific disease. The biological samples were obtained during assisted reproductive treatment (ART) by the biopsy of oocyte polar bodies or embryos. PGD requires a multidisciplinary and highly experienced team in ART and genomic evaluation at single-cell level [15, 16].

*Indications for PGD*. Usually, PGD is provided to couples at risk of conceiving abnormal offspring with monogenic or chromosomal disorders. Thus, PGD is suitable for couples where one member is affected by a dominant disorder or both are known carriers of mutant alleles for a recessive disease, or one of them carries a balanced chromosome rearrangement that predisposes him/her to transmit and unbalanced chromosomal abnormality, often deletion or duplication [16, 17]. The presence of a gene mutation or chromosomal abnormality in a member or members of a family must be identified before PGD to allow the detection of a particular genetic abnormality before implantation and further the transmission of a specific disorder to children. Only normal embryos are transferred to the uterus to initiate the pregnancy knowing that the embryo is not a carrier for a specific abnormality, thus decreasing the risk of having an offspring affected by a specific genetic disorder. Many of these diseases are associated with an early death or severe mental and congenital abnormalities. The monogenic diseases diagnosed through PGD include autosomal recessive conditions (e.g., β-thalassemia, cystic fibrosis, spinal muscular atrophy, and sickle cell disease), autosomal dominant conditions (Huntington's disease, myotonic dystrophy, and Charcot-Marie-Tooth disease), or X-linked recessive conditions (fragile X syndrome, Duchenne muscular dystrophy, and hemophilia) [18].

PGD is also available to help parents in creating embryos that are human leucocyte antigen (HLA) compatible with a child affected by a severe blood disease, thus the selected sibling serving as a donor. PGD is an appropriate choice for carrier couples who also have infertility problems and plan to use assisted reproductive treatment anyway or for couples with an ethical or religious objection to pregnancy termination. PGD can also be used for the detection of a variety of cancer predispositions (e.g., familial breast cancer) [19, 20].

*Biopsy procedures and genetic analysis technique.* Genetic testing can be performed using biological samples obtained by one of the following: polar body, cleavage-stage embryo, or blastocyst biopsy [15, 16].

The indirect setting, based on family history, of an increased individual risk of the disease will allow for the direct determination by molecular tests of genetic risk factors, possibly specific

To summarize, genetic counseling in isolated congenital anomalies relies on information gathered from population-based studies, on new and future discoveries related to the etiology of these disorders, and other factors such as the degree of kinship with the proband, presence of a more severe condition, more than one individual affected in the same family, or

Genetic counseling is about guidance and support for the patient and the patient's family, so a great deal of attention must also be directed toward careful wording when explaining the

Preimplantation genetic diagnosis is a multistep procedure that analyzes the genetic material from a single or several cells, with the purpose to avoid a pregnancy affected by a specific disease. The biological samples were obtained during assisted reproductive treatment (ART) by the biopsy of oocyte polar bodies or embryos. PGD requires a multidisciplinary and highly

*Indications for PGD*. Usually, PGD is provided to couples at risk of conceiving abnormal offspring with monogenic or chromosomal disorders. Thus, PGD is suitable for couples where one member is affected by a dominant disorder or both are known carriers of mutant alleles for a recessive disease, or one of them carries a balanced chromosome rearrangement that predisposes him/her to transmit and unbalanced chromosomal abnormality, often deletion or duplication [16, 17]. The presence of a gene mutation or chromosomal abnormality in a member or members of a family must be identified before PGD to allow the detection of a particular genetic abnormality before implantation and further the transmission of a specific disorder to children. Only normal embryos are transferred to the uterus to initiate the pregnancy knowing that the embryo is not a carrier for a specific abnormality, thus decreasing the risk of having an offspring affected by a specific genetic disorder. Many of these diseases are associated with an early death or severe mental and congenital abnormalities. The monogenic diseases diagnosed through PGD include autosomal recessive conditions (e.g., β-thalassemia, cystic fibrosis, spinal muscular atrophy, and sickle cell disease), autosomal dominant conditions (Huntington's disease, myotonic dystrophy, and Charcot-Marie-Tooth disease), or X-linked recessive condi-

consanguinity for calculating the recurrence risk for the respective condition.

experienced team in ART and genomic evaluation at single-cell level [15, 16].

tions (fragile X syndrome, Duchenne muscular dystrophy, and hemophilia) [18].

a variety of cancer predispositions (e.g., familial breast cancer) [19, 20].

PGD is also available to help parents in creating embryos that are human leucocyte antigen (HLA) compatible with a child affected by a severe blood disease, thus the selected sibling serving as a donor. PGD is an appropriate choice for carrier couples who also have infertility problems and plan to use assisted reproductive treatment anyway or for couples with an ethical or religious objection to pregnancy termination. PGD can also be used for the detection of

medical actions of early diagnosis.

458 Congenital Anomalies - From the Embryo to the Neonate

risk and decisions that need to be made.

**5. Preimplantation genetic diagnosis (PGD)**

Polar body biopsy. First and second polar bodies are haploid cells produced in the first and, respectively, second meiotic division of oogenesis. The genetic evaluation of both polar bodies is required to precisely establish the genetic status of the oocyte. Because polar bodies are not a part of the zygote, this technique is mainly performed in some countries where embryo biopsy is unauthorized by law. Polar body analysis only provides data about mutations or aneuploidies of maternal origins. The chromosome abnormalities occurring postmeiotically (e.g., mosaicism and polyploidy), limited amount of genetic material, and doubling the number of samples for analysis have made the need to perform this type of biopsy questionable [36, 21].

Cleavage-stage embryo biopsy. Cleavage-stage biopsy is usually performed on day 3 when early embryo consists of approximately 6–10 cells. At this stage, the cells are still totipotent and are not yet adhering to one another, allowing the extraction of a single blastomere for genetic testing. Limited amount of genetic material and high rates of mosaicism observed in early embryos can lead to misdiagnosis at this stage. The biopsy of two blastomeres was associated with deleterious effects on embryo development and is recommended to be avoided [22, 37].

Blastocyst biopsy. The embryo reaches the blastocyst stage on day 5 or 6 after fertilization. The blastocyst contains about 100 cells and comprises the outer trophectoderm and inner cell mass. During blastocyst biopsy, 5–10 trophectoderm cells are retrieved; thus, more material for genetic diagnosis is available. The ethical and safety considerations related to early embryo biopsy are overcome somewhat because the trophectoderm cells will differentiate into trophoblast cells and further go on to form placenta and other extraembryonic tissues, and not participate to form the embryo [15, 23]. Recent studies showed that this type of biopsy has no effect on reproductive capacity of a blastocyst [16, 24]. However, only about 40–50% of preimplantation embryos will reach this stage in vitro. Because the time to obtain a genetic diagnosis is very limited to perform a fresh embryo transfer, mostly frozen embryo transfer is performed after vitrification [15, 16, 36].

*Genetic analysis techniques.* After the biological material is available for biopsy, the genetic analysis can be performed. The evaluation is based on only a single cell or very limited genetic material. For fresh embryo transfer, the genetic diagnosis must be done within 24–36 h. The single-gene mutations are detected using molecular genetic methods (PCR, PCR-multiplex, RTqPCR, whole genome amplification, or even next-generation sequencing) and chromosomal abnormalities (e.g., translocation and aneuploidies) by cytogenetic techniques (FISH, array CGH, and SNP array) [16, 25].

The embryo testing using genetic methods with the aim to detect *de novo* chromosomal aneuploidies is known as preimplantation genetic screening (PGS) [26]. PGS analyzes whether a single cell or a small number of cells biopsied from a preimplantation embryo is euploid before transferring it to the uterus. PGS is not PGD, being mainly offered to couples with advanced maternal age, recurrent implantation failure or recurrent miscarriages, and other conditions associated with high risk for aneuploid embryos in order to increase the success rate of IVF (~30%). PGS can be performed using FISH, multiplex quantitative PCR, or chromosomal microarrays [16, 27, 28].

*Genetic counseling.* A clinical genetic consultation provided by a geneticist with practice in ART is required to the couples before starting PGD treatment. Its purpose is to confirm the genetic diagnosis, to evaluate the reproductive status of the couple, and to provide information about the disease, mode of inheritance, recurrence risk, genetic testing, and reproductive options, including PGD [38].

Medical genetics is one of the medical fields in which, from the very beginning, sensitive ethical issues have been raised; their importance subsequently became more and more undeniable due to technological advances and discoveries in the field (see Human Genome Project,

Prenatal Genetic Counseling in Congenital Anomalies http://dx.doi.org/10.5772/intechopen.74394 461

Of all the areas of genetics, prenatal diagnosis raises the most fervent debates and, consequently, ethical dilemmas. It is one of the chapters that are hard to fit in an accurate guide for the clinician, sufficient enough to use and make sure he has done or said what is needed to

The particularity of this field is derived from the existence of two entities whose rights must be taken into account: on one hand, the "patient," the unborn fetus at different stages of development at the time of the diagnosis request, and on the other hand, the mother/couple requesting the diagnosis. Although the phrase"on one hand and … on the other side" might seem inappropriate, it still reflects reality, because not always the rights of the patient are on the same side as those of the parents. And here lies the first dilemma: autonomy vs. benefit.

In order to improve medical practice in medical genetics and implicitly in prenatal genetic diagnosis, a set of essential ethical principles was developed to support a clinical decision

**1.** Respecting the autonomy of a person referring to the right of a patient to make his/her own decision without any constraint but at the same time informed by a genetic counseling in

**2.** The "do not harm" obligation and the "doing good" duty reflect on the degree of necessity of the two desires. Obviously, it is desirable to do well (benefit), but in this process, it is much more important to avoid mistakes before getting the right benefit (e.g., presympto-

**3.** Confidentiality protects the patient's genetic data from various other parts. The data could be provided only with the patient's consent and only if the doctor considers them relevant. However, the doctor may not respect confidentiality if the genetic data are relevant for the relatives and the patient is not able to properly inform them about familial medical

**4.** Equal access to patients for care and treatment: this concept is the most difficult to apply

Prenatal diagnosis (PD), and here we will only refer to invasive PD, involves a genetic test that allows the diagnosis of a fetus with a serious genetic disorder (and there is an issue of what "serious" means in the opinion of specialists), followed by communication of the data to parents. The purpose of prenatal genetic testing is exclusively medical and testing criteria

When PD is recommended, the couple will be informed, regardless of their perspective on abortion because sometimes it can be useful for psychological and medical training for the

Next Generation Sequence, and Whole Genome/Exome Sequencing).

ensure that the health of the patient and family is protected.

a nonlinear and impartial manner, without prejudices.

**6.1. Ethical principles and prenatal counseling**

matic testing for early-onset diseases) [33].

due to the insufficient resources.

should be clearly established [34].

[32, 35]:

conditions.

Genetic counseling by a qualified geneticist or a certified genetic counselor is recommended to the couples to receive support and appropriate information in a nondirective manner and with no pressure, allowing them to make the best choice. Family history, reason for PGD, what is PGD, alternative reproductive options and side effects of treatment, the limitations of testing, success rates (about 30%), and possible outcome options should be discussed, including an unsuccessful cycle [29, 30].

Also, a multiple birth should be considered when ART is used. Thus, the couple should understand and consider the physical, psychological, and financial impact of treatment [31].

An important part of genetic counseling is to establish the reason for choosing PGD. In most cases, the couples choose PGD to avoid termination of pregnancy due to a genetic disease or to know earliest that the pregnancy is unaffected by a specific genetic abnormality [17]. Other reasons for PGD include a previously affected child or a loss of a child, recurrent abortions, or infertility. When parents are carriers for a recessive disorder, more embryos may be carriers for a mutant allele. The couple must be informed about the genetic status of the embryos and in the absence of a clinical feature in carriers, these can be considered for transfer to increase the number of available embryos. The issue of genetic testing of children for carrier status should be discussed prior to offering prenatal diagnosis to confirm the PGD result.

Sex selection is not allowed by law in many countries, while in others, it is allowed. Except some recessive X-linked disorders where females may have a mild phenotype, in these cases, the female embryos should be excluded for transfer, and the parents should be able to choose not to know the sex of their embryos.

After implantation, a new contact with a geneticist is required. Occasionally, when PGD is used, a misdiagnosis can occur; therefore, prenatal diagnosis should be offered. Prenatal diagnosis requires an invasive testing (chorionic villus sampling and amniocentesis) associated with the risk of losing the pregnancy, and many of them may refuse the confirmatory test [29].

The postnatal confirmatory diagnosis from blood is in contrast to recommendations for testing in childhood, which specify that unless there are clinical benefits to testing minors, testing for carrier or late disease conditions should be delayed until the child is old enough to understand the implications and be part of the decision making. In most cases, a successful PGD cycle will result in an ongoing pregnancy and a healthy live born infant. However, a follow-up after birth is recommended.
