Recurrent Pregnancy Loss

• When a  couple has three subsequent pregnancy losses before 20 weeks from the last menstrual period, it is termed recurrent pregnancy loss
• For 50 % of such cases, an underlying cause can be established
• Esher Guidelines ( 2018 ) state that any woman with such a condition should be evaluated for
  • Uterine anomalies/cervical anomalies
  • Infections
  • Thrombophilia
  • Endocrinological reasons
  • ANA
  • Immunological Factors
  • Genetic Factors

• Among genetic factors, chromosomal factors have an established role in early pregnancy loss. The most common reason for spontaneous miscarriage is embryonal aneuploidy. If DNA from the product of conception of the last miscarriage is stored its an added advantage s this can be investigated
• One of the partners can have a balanced translocation. Individuals with balanced translocation in chromosomes are at a higher risk for pregnancy loss due to an increased chance of embryonal aneuploidy
• Recurrent pregnancy loss can be also due to single gene disorders related to thrombophilia, cardiac-related genes, neuromuscular related genes or genes related to hydrops fetalis, or genes associated with conditions like hydrocephalus, or other rare genetic conditions
• A good genetic clinic will evaluate all the clinical h/o, will take a three-generation family history and look at all the biochemical and clinical diagnostic, explain to the couple, and further guide the couple for an appropriate investigation to understand the cause
• If a cause is identified then couples can have different options based on their social, economical, and religious preferences. Any identified cause can be managed, even if it’s a genetic cause. Very rarely will there be a cause that cannot be intervened?
• If no cause is identified then the couple will be guided by the fertility specialist for further management through scientific and clinical evaluation

What is Non-Invasive Prenatal Testing?

• Non-Invasive Prenatal Testing NIPS is a method for determining the risk of a fetus with chromosomal aneuploidy. The mother’s blood has DNA that is derived from the placenta/ apoptotic trophoblast cells and can cross the placenta into the mother’s bloodstream. This DNA is called Cell-Free DNA ( cf DNA ) and its circulation peaks in the bloodstream of the mother around 9 to 23 weeks of gestation.  The NIPS analyzes this cfDNA for screening for aneuploidy. The fetal fraction in the mother’s blood for cfDNA is influenced by the BMI of the mother, gestational age,  type of and singleton vs multiple pregnancies.
• Most commonly the test is suggested to screen for trisomy 21, trisomy 18, trisomy 13,  and gonosomal aneuploidy.  However, aneuploidy screening for other chromosomes is also possible. The sensitivity depends on the fetal fraction present in the bloodstream and varies according to the disorder. The test is more sensitive than the biochemical marker testing  ( dual/ quadruple ) available.
• The test involves a simple blood test, however, the collection tube is a special tube called a streak tube. This ensures that the cf DNA is not degraded. As this does not require testing of the placental tissue or the amniotic fluid, hence this is called non-invasive and thus is risk-free for the fetus.
• There are different technical platforms by which this nip is done. Depending on if you have a twin pregnancy, etc your gynecologist or genetic counselor can help you choose the correct NIPS.   The most well-accepted method is to count all cfDNA fragments (both fetal and maternal). If the percentage of cfDNA fragments from each chromosome is within the expected threshold then there is decreased risk of having a chromosomal condition (negative test result). However,  if the percentage of cfDNA fragments from a particular chromosome is more/ less than the threshold, then the fetus has an increased likelihood of having an aneuploidy  (positive test result).
• Women of advanced maternal age or women having intermediate risk in the screening test for combined FTS/ Quadruple test can be offered. However, anyone  who is suggested a dual screening / quadruple screening can be suggested a NIPS
• NIPS is a screening test, which indicates that testing by this method would help in understanding the risk, however, for a definitive answer, further invasive tests should be conducted  The test can only screen the risk of having certain chromosomal aneuploidy. NIPs involve testing both the fetal and maternal cfDNA and hence can detect an underlying genetic condition in the mother.
• The test can only screen for chromosomal aneuploidy and is not meant to screen for single gene disorder at this moment. Additionally, NIPS will not be able to pick up unbalanced translocation or micro del/ duplication, hence, couples who are a known cause for balanced translocation/ Robertsonian translocation / has a previous fetus with microdeletion/ duplication cannot be suggested this test and have to go for invasive testing methods.

 

Can normal couples have a child who is affected by a  genetic disorder?

• India is a land where we have different marriage customs and many times we are married in the same community.  This process of endogamy is very dominant in India. Due to this, there is an increased chance that altered genetic traits get accumulated leading to autosomal recessive or X- linked disease, thus making India a “melting pot”  for genetic disorders.  In 2008-2009, WHO has stated that in India the incidence of the non-communicable disorders is more than communicable disorders
• American counsel for Medical Genetics(ACMG ) recommends all couples who are planning a pregnancy, especially couples planning an IVF pregnancy for a  basic carrier screening
• Autosomal recessive disorders will not have a family history most often, also h/o neonatal death, etc might not be known/disclosed. Parents can be carriers and hence there can be a 25 % chance that the children of totally healthy individuals would be affected.  Similarly for X-linked disorders, there might be male members who are affected while female members who are asymptomatic, and females can be carriers while their male children can have a 50 % chance of being affected.
• Carrier screening is used to screen individuals or couples who are at risk to have babies with an autosomal recessive or X-linked genetic disorder. “Carrier” refers to people who are heterozygous for a pathogenic /likely pathogenic variant in an autosomal recessive or X-linked condition.  These individuals are asymptomatic and might or might not have a family history.
• If a screening test identifies carriers of such genetic disorders they can be informed about their risks and consider a range of reproductive options.
• Carrier screening cannot eliminate the risk of being a carrier of a heritable condition, because all genes that cause a condition may not be known or all genes that cause a condition may not be examined.
• Diseases associated with neuro-development, Epilepsy, Neuro-muscular,  Cardiovascular,  renal pathologies, Cystic kidney disorders,   metabolic disorders, CAH, Cystic fibrosis, Intellectual Disability, blood disorders, Primary immune deficiencies, and a few cases of Autism Spectrum disorder can be ruled out.
• A good genetic counselor would take a three-generation pedigree and inform you for   understanding your risk to have such a child  and  thereby help in   planning your pregnancy
• There is prenatal genetic screening available to understand the status of the fetus in terms of the risk identified and also preimplantation genetic testing that can help you plan a healthy baby.

Ref:  https://www.nature.com/articles/s41436-021-01203-z.pdf

The process of  CVS  /  Amniocentesis:  does it rule out all genetic tests?

• Chorionic villus sampling (CVS) and amniocentesis are prenatal invasive diagnostic procedures that are performed to confirm a  fetal genetic/chromosomal/infectious problem. CVS utilizes either a catheter or needle to biopsy placental cells of the fetus. During amniocentesis, a small amount of the fluid that surrounds the fetus is taken out. This fluid contains cells that are derived from the fetal skin, bladder, gastrointestinal tract, and amnion. Typically, CVS is done at 10-12 weeks’ gestation, and amniocentesis is done at 15-18 weeks’ gestation.
• Although the maternal age-related risk for fetal aneuploidy post  a First-trimester screen / Quadruple screen / NIPS  is the usual indication for CVS or amniocentesis,  fetal anomaly   visualized at 16 to 20 weeks scan  can also be recommended  for such tests
• Moreover, couples who are carriers ( they are asymptomatic but carry a gene mutation in heterozygous condition )  for single gene disorders like thalassemia, or have a previously affected child with the identified genetic problem might be recommended for fetal testing when they are at risk for passing on certain Mendelian (single-gene) conditions.
• A genetic counselor/ medical geneticist would recommend testing based on the three-generation family h/o or based on the screening report or the fetal USG report. In most cases, these tests would be targeted for a particular condition and would answer only the status of that condition and are not encompassing all and every genetic condition.
• It is also important to know that risk for miscarriage, for such procedures has been attributed to 0.5%-1.0% for CVS procedures and 0.25%-0.50% for amniocentesis procedures. However,  most  genetic conditions don’t have a cure and  these procedures help the couple to make an informed decision
• At present the Government of India, PCPNDT act allows termination of pregnancy with a genetic condition  till 24 weeks, and post this  the  medical board and court have to be informed

Thalassemia Screening

• Thalassemia is a condition where the body makes abnormal hemoglobin. This is the most common inherited blood disorder.
• The Red blood cells have a protein molecule called Hemoglobin that carries oxygen. In Thalassemia,  there is the destruction of these RBCs leads to anemia.
• Thalassemia is inherited in an autosomal recessive manner, which means the parents are carriers, and two bad mutations in the gene in trans position would lead to disease.   Thalassemia minor is a less serious form of the disorder.
• Two main forms of thalassemia are more serious. In alpha thalassemia, at least one of the alpha-globin genes has a mutation or abnormality. In beta-thalassemia, the beta-globin genes are affected. There are other forms of thalassemia like HBD, HBE, and HbS.
• Not all thalassemia leads to blood transfusion or needs prenatal testing.
• Every couple is screened for beta-thalassemia by HLP along with CBC and peripheral blood smear. The biochemical values and the retention peak indicate the kind of thalassemia.  A medical geneticist would be able to guide you if you would need further testing or a prenatal diagnosis.

• HBB gene and that 200 variations lead to Beta-thalassemia. There are variations in Beta-thalassemia that can be of intermediate effect and in those cases, transfusion may not be needed. However, if it is a variant that is known to cause major beta-thalassemia that would mean a transfusion-dependent thalassemia
• It was explained that the chances of a child affected with Beta-thalassemia are 25  % if both parents are carriers while the chances that the child will be a carrier like the parents are 50%  and the chances that the child will have the normal variants is 50 %.
• There are a few types of Thalassemia that do not cause any problem even if inherited and may present with mild anemia.
• Prenatal screening by CVS from 13 weeks to 15 weeks or amniocentesis from 15 to 18 weeks for Thalassemia can be done if parents are carriers for any thalassemia that would lead to a severe phenotype and would need a transfusion.
• Additionally, pre-implantation testing ( IVF-PGT ) / gamete donation are also available.
• Couples who already have a child who is affected and under transfusion can also  have the option of HLA typing in the embryos by pre-implantation testing

Genetic risk in Autism spectrum disorder and the chance of recurrence in a subsequent pregnancy

• Autism spectrum disorder (ASD) is associated with neurodevelopment that impacts social interaction and communication. The disorder also includes limited and repetitive patterns of behavior. The term “spectrum” in autism spectrum disorder refers to the wide range of symptoms and severity.
• Autism is a spectrum disorder and may be due to environmental and/or genetic factors.
• According to recent literature, a potential underlying genetic cause can be identified in nearly 40% of cases. However, not all genetic causes for autism are inherited. There can be de novo spontaneous mutation  leading to such manifestations also
• We all have 46 chromosomes. An increase or decrease in the number causes aneuploidy that leads to diseases specific to that chromosomes. These diseases can have symptoms that fall in the autism spectrum.  Further, more chromosomal deletion and duplications have been attributed to causing autism spectrum disorder. The most common CNV found in ASD patients are located at 15q11-13, 16p11, and 22q11-13, which altogether have an incidence of around 3 to 5%.  The recurrence chances for these are low unless the parent has a balanced translocation.  Prenatal testing can be done in these cases.

• ASD can be part of the manifestations observed in monogenic and metabolic disorders like Fragile X, Rett syndrome, Cowden syndrome, etc. These can be inherited and can have a recurrence risk.  Prenatal testing can be done in these cases.
• De novo disruptive single nucleotide variants are estimated to be found in around 8 to 20% of ASD cases. The recurrence risk for such de novo changes is very low, prenatal diagnosis is recommended for these to rule out gonadal mosaicism,
• A good genetic clinic would evaluate the affected child by physical appearance ( dysmorphology ), evaluate the symptoms the scoring used to diagnose the child and family history, along with biochemical and molecular testing for known metabolic disorders. On basis of these genetic testing would be conducted. If a clinically relevant genetic cause is identified depending on what was identified, a genetic counselor would guide towards parental testing if needed and further prenatal diagnosis.
• However, it is worth noting that many well-known ASD-related variants are associated with susceptibility to other psychiatric phenotypes or incomplete penetrance, hampering a reliable estimation of recurrence risk. In cases of ASD with no identifiable cause, recurrence risk is based on empirical observations: for a couple with one affected child, it is calculated to be around 3 to 10%, and it can be considered higher (~7%) if the affected child is a female, or lower (~4%) if the affected child is a male. Also, having two or more affected children, the recurrence risk rises to 33 to 50%.

• According to the American Association of Pediatrics, there would be genetic investigations needed to be done on the affected child. And in some cases targeted testing for parents might also be suggested
• If any clinically relevant/genetic variants are identified then preimplantation genetic testing /  prenatal diagnosis in the fetus by  CVS at 9- 13 weeks or by amniocentesis at 15 to 18 weeks can be offered.

Ref: Autism spectrum disorders: an updated guide for genetic counseling, Karina Griesi-Oliveira, Andréa Laurato Sertié, einstein. 2017;15(2):233-8

What is Hereditary Breast and Ovarian Cancer?

Cancers can have a genetic etiology, however, only some cancers are hereditary. About  5% to 10% of breast cancers are inherited and can be attributed to abnormal genes passed from parent to child. When there are multiple affected family members with breast / ovarian / prostate cancer/ pancreatic cancer in the family along with certain immune markers a  risk for Hereditary Breast and Ovarian Cancer Syndrome (HBOC) is considered. The risk in a family for HBOC increases in any of these situations:

• 1 or more women are diagnosed at age 45 or younger
• 1 or more women are diagnosed with breast cancer before age 50 with an additional family history of cancer, such as prostate cancer, melanoma, and pancreatic cancer
• There are breast and/or ovarian cancers in multiple generations on the same side of the family, such as having both a grandmother and an aunt on the father’s side both diagnosed with these cancers
• A woman is diagnosed with second breast cancer in the same or the other breast or has both breast and ovarian cancers
• A male relative is diagnosed with breast cancer
• There is a history of breast cancer, ovarian cancer, prostate cancer, and/or pancreatic cancer on the same side of the family

What causes HBOC?

HBOC is inherited in an autosomal dominant manner. If there is an affected family member there is a risk associated to pass on the same to the next generations. The most well-known genes commonly associated in most families are BRCA1 and BRCA2:  A change in the genetic code in either BRCA1 or BRCA2 gives a woman an increased lifetime risk of developing breast and ovarian cancers. Even men can have a risk of breast cancer and prostate cancer if they inherit such a mutation. However, other genes are also associated with increased breast / ovarian cancer like in the TP53, PTEN, CDH1, ATM, CHEK2, or PALB2 tumor suppressor genes, etc have also been reported.  A genetic screening test can pick up and identify such mutations.

How common is HBOC?

Most breast and ovarian cancers are not inherited and are de novo  /  occur by chance with no known cause.  It is estimated that about 10% to 30% of women younger than 60 diagnosed with “triple-negative” breast cancer, ( ER-negative, PR negative, and HER 2 negative ) have a risk for a BRCA1 / BRCA2 gene mutation, / other gene such mutations. Therefore, doctors would recommend that women with triple-negative breast cancer receive genetic counseling and genetic testing.

HBOC is most common in families who have had multiple cases of breast cancer and/or ovarian cancer on the same side of the family. In families with 4 or more cases of breast cancer diagnosed before age 60, the chance of HBOC is about 80%. To compare, the chance of finding HBOC when only 1 woman has had breast cancer diagnosed before age 50 is estimated to be 10% or less.

If a person has a BRCA1/ 2 mutation and wants to have a child, it is important for the other prospective parent to also be tested before pregnancy. If both parents carry a BRCA2 gene mutation, there is a 25% risk of having a child with Fanconi anemia, which is an inherited disorder, associated with physical abnormalities, an increased risk of blood cancers, and other serious problems. Fanconi anemia is inherited in an autosomal recessive pattern, meaning that if a child inherits a copy of the BRCA2 gene with a mutation from each parent, that child will be born with the disorder.

Who should be tested for HBOC?

Genetic testing is recommended primarily for people who have a personal and/or family history that suggests HBOC. However, women younger than 60 with triple-negative breast cancer are at risk of having a BRCA mutation, regardless of family history.

For women with a previous diagnosis of breast cancer or ovarian cancer and/or a family history of breast or ovarian cancer, the National Comprehensive Cancer Network (NCCN) provides recommendations for when genetic counseling and testing may be needed. These recommendations are based on your family’s history of cancer and how closely related you are to the person(s) who developed cancer. Here are some important definitions to know:

• “First-degree relatives” include parents, siblings, and children.
• “Second-degree relatives” include aunts/uncles, grandparents, grandchildren, and nieces/nephews.
• “Third-degree relatives” include first cousins, great-grandparents, or great-grandchildren.

Genetic testing should be considered if a person or family meets 1 or more of the criteria listed below:

• A family member has a known mutation in the BRCA1 or BRCA2 genes or other related breast cancer risk genes
• A personal history of breast cancer plus 1 or more of the following:
  • A diagnosis of breast cancer at age 45 or younger
  • A diagnosis of breast cancer between ages 46 and 50 with:
    • A diagnosis of second breast cancer in the same or another breast
    • 1 or more first-, second-, or third-degree relatives on the same side of the family diagnosed with the breast at any age
    • A diagnosis of high-grade prostate cancer in 1 or more first-, second-, or third-degree relatives on the same side of the family
    • An unknown or limited family history
    • A diagnosis at age 60 or younger with triple-negative breast cancer (see above)
  • A breast cancer diagnosis at any age with:
    • A personal history of ovarian cancer
    • 1 or more first-, second-, or third-degree relatives on the same side of the family diagnosed with breast cancer at age 50 or younger, ovarian cancer, pancreatic cancer, metastatic prostate cancer, or breast cancer in a male relative. “Metastatic” means cancer that has spread from where it started to another part of the body.
    • 2 additional first-, second-, or third-degree relatives on the same side of the family diagnosed with breast cancer at any age
    • Being in a family of Ashkenazi Jewish ancestry
  • A personal history of male breast cancer
  • A personal history of metastatic prostate cancer
  • A personal history of high-grade prostate cancer at any age plus 1 or more of the following:
    • Having 1 or more first- or second-degree relatives who meet any of the criteria above
    • 1 or more first-, second- or third-degree relatives on the same side of the family with ovarian cancer, pancreatic cancer, or metastatic prostate cancer diagnosed at any age or breast cancer diagnosed younger than 50
    • 2 first-, second-, or third-degree relatives on the same side of the family with breast or prostate cancer diagnosed at any age.
    • Being in a family of Ashkenazi Jewish ancestry

What can I do to reduce my risk of developing breast cancer or ovarian cancer if I have a BRCA gene mutation?

• Risk-reducing surgery
• Chemoprevention

What are the screening options for HBOC?

Screening for women with a BRCA1 or BRCA2 gene mutation

• Monthly breast self-examinations, beginning at age 18
• Clinical breast examinations are performed twice a year by a health care team or nurse, beginning at age 25
• Yearly magnetic resonance imaging (MRI) scans of both breasts, between ages 25 and 29.
• Yearly mammogram and breast MRI, between ages 30 and 75.
• Pelvic (gynecologic) examination, a transvaginal ultrasound, and CA-125 blood test every 6 months beginning at age 30 to 35. It should be noted, however, that screening is not yet able to find most early ovarian cancers.
• Consideration of prophylactic salpingo-oophorectomy, between ages 35 and 40, and once a woman is done giving birth to children

Screening for men with a BRCA1 or BRCA2 gene mutation

• Monthly breast self-examinations, beginning at age 35
• Yearly clinical breast examinations, beginning at age 35
• Consider a baseline mammogram at age 35 for men with a BRCA2 gene mutation, if there is gynecomastia, meaning swelling of the breast tissue in boys or men, or if enough breast tissue is present for mammogram
• Yearly prostate cancer screening with digital rectal exam and PSA blood test, beginning at age 45.

Adapted from: https://www.cancer.net/cancer-types/hereditary-breast-and-ovarian-cancer