In the United States, approximately 1 in 33 infants are born with a birth defect, encompassing a wide array of physical changes that take place during fetal development. These alterations can affect both the outward appearance and internal functionality of the affected organ. Birth defects have the potential to impact many parts of the developing body and can manifest with varying degrees of severity, ranging from mild to severe. The well-being and life expectancy of individuals affected by birth defects depend upon the specific body part involved and the extent of its impact on the overall function of that particular organ or area.

What are the most common causes of birth defects?

Birth defects can be caused by environmental factors, genetic factors, or a combination of both. 

• Environmental Factors: Exposure to certain substances or maternal health conditions (such as diabetes) during pregnancy can increase the risk of birth defects. These may include maternal infections, drug and alcohol use, exposure to radiation or chemicals, and inadequate prenatal care.
• Genetic Factors: Changes or mutations in a baby's genes and/or chromosomes can lead to birth defects. These genetic abnormalities can be inherited from parents or occur spontaneously during conception.

• Approximately 25% of individuals with a birth defect have an identified genetic cause, though this percentage varies based on the type of birth defect⁵. For instance, in the case of cardiac anomalies, the most common type of birth defect, approximately  20-30% of affected individuals have an identified genetic cause.

• Multifactorial Causes: In many cases, birth defects result from a complex interplay of genetic and environmental factors. These multifactorial causes make it challenging to pinpoint a single determinant. 

When are birth defects identified?

Birth defects can be diagnosed either during pregnancy or after the baby is born, with prenatal ultrasound imaging serving as a non-invasive option to detect and identify potential birth defects. During pregnancy, the nuchal translucency (NT) ultrasound, typically offered to women with higher risk pregnancies, examines the presence of excess fluid behind the baby's neck, indicating possible chromosomal disorders or heart defects. The Anatomy ultrasound, conducted around 18-20 weeks, assesses the baby's size and screens for potential birth defects or complications. Some birth defects may only be detected after birth, requiring further medical history, physical examination, and specialist evaluations for an accurate diagnosis.

Genetic screening and diagnostic testing play a crucial role in assessing the risk of chromosomal conditions that can lead to birth defects. Screening tests, such as noninvasive prenatal screening (NIPS) and or other first/second trimester screening, involve blood tests and ultrasounds to evaluate the likelihood of chromosomal abnormalities. Diagnostic tests, including high-resolution ultrasounds, chorionic villus sampling (CVS), and amniocentesis, are performed when screening results indicate a higher risk or abnormalities.

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Can birth defects be prevented?

Although the risk for birth defects can never be completely eliminated, preconception planning is crucial for reducing the occurrence of birth defects. This includes:

• Maintaining overall health: adopting a balanced diet, managing pre-existing conditions, avoiding harmful substances, and seeking guidance from healthcare professionals. For example, taking folic acid supplements before conception is particularly recommended as it plays a vital role in minimizing the risk of certain birth defects, especially neural tube defects. For more recommendations from the American College of Obstetricians and Gynecologists, click here.
• Genetic Screening options: Family history of birth defects may increase the chances of birth defects in offspring. Engaging in conversations about your family history with a genetic counselor and/or obstetric provider can prove invaluable in identifying any additional recommendations or precautions that may be necessary.‍
• Carrier screening: A genetic test that examines the DNA of prospective parents to determine if they carry a gene that could cause a genetic disorder leading to birth defects. Being a carrier means having a faulty gene that can be passed on to their children, even if the parents themselves do not have the disorder. The results of this screening can indicate if you are at risk of passing on a genetic condition to future children, potentially resulting in the occurrence of birth defects.‍
• Embryo Screening: Only Orchid is able to screen for genetic forms of birth defects and can reduce the chances of inherited and non-inherited (de novo) genetic changes known to cause birth defects for each embryo.
  If your offspring is at increased risk for a known genetic condition, Orchid can help you select embryos that did not inherit the genetic condition seen in your family (or identified through carrier screening). It is important to note that embryo screening does not replace traditional diagnostic tests during pregnancy.

A note on Genetic Screening options: Just because a birth defect is influenced by genetics does not mean it was inherited from a parent. Anyone has a chance of having a pregnancy with a genetic cause for birth defects. This is because a vast majority of genetic birth defects happen by chance in an individual (called "de novo") In particular, if you are of advancing maternal age (>35) or advancing paternal age (>40), there may be an increased chance of these randomly occurring (de novo) chromosomal and/or genetic conditions that lead to birth defects^8,9.

Once a pregnancy is achieved, early and regular prenatal care plays a crucial role in identifying and managing risk factors. This includes:

• Environmental Factors: Avoiding harmful substances such as tobacco, alcohol, and illicit drugs during pregnancy is crucial. Following a healthy lifestyle, including a balanced diet, regular exercise, and stress management. 
• Prenatal Care: Attend prenatal visits, follow recommended screening and diagnostic tests, and adhere to their healthcare provider's advice.
• Genetic screening: Screening tests, like noninvasive prenatal screening (NIPS), or other first and second trimester screening which involve blood tests and ultrasounds to assess the risk of chromosomal conditions that can lead to certain birth defects. 

While the prevention of birth defects may not be entirely within our control, there are steps we can take to mitigate the risks, such as adopting a healthy lifestyle, seeking appropriate medical care before and during pregnancy, and undergoing genetic counseling and testing when necessary. At Orchid, we are passionate about empowering patients with knowledge to mitigate the most risk for their future children. Only through Orchid can patients screen their embryos for hundreds of genes associated with birth defects, all prior to pregnancy. 

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References
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<sup>1. Center for disease control and prevention. Birth Defects are Common, Costly, and Critical. Retrieved from:www.cdc.gov/birthdefects
2. Center for disease control and prevention.What are Birth Defects? Retrieved from: https://www.cdc.gov/ncbddd/birthdefects/facts.html
3. American College of Obstetricians and Gynecologists. Pregnancy With Type 1 or Type 2 Diabetes. Retrieved from: https://www.acog.org/womens-health/faqs/pregnancy-with-type-1-or-type-2-diabetes
4. Center for disease control and prevention. Birth Defects Surveillance Toolkit. Retrieved from: https://www.cdc.gov/ncbddd/birthdefects/surveillancemanual/appendices/appendix-c.html
5. Stevenson RE, Hall JG, editors. Human malformations and related anomalies, second edition. Oxford: Oxford University Press; 2006.
6. Wojcik, M. H., & Agrawal, P. B. (2020). Deciphering congenital anomalies for the next generation. Cold Spring Harbor molecular case studies, 6(5), a005504. 
7. Center for disease control and prevention. Folic Acid Recommendations. Retrieved from:https://www.cdc.gov/ncbddd/folicacid/recommendations.html
8. Boskovski et. al. De Novo Damaging Variants, Clinical Phenotypes, and Post-Operative Outcomes in Congenital Heart Disease. Circ Genom Precis Med 2020;13: e002836 PMID: 32812804
9. Taylor, J. L., Debost, J. P. G., Morton, S. U., Wigdor, E. M., Heyne, H. O., Lal, D., Howrigan, D. P., Bloemendal, A., Larsen, J. T., Kosmicki, J. A., Weiner, D. J., Homsy, J., Seidman, J. G., Seidman, C. E., Agerbo, E., McGrath, J. J., Mortensen, P. B., Petersen, L., Daly, M. J., & Robinson, E. B. (2019). Paternal-age-related de novo mutations and risk for five disorders. Nature communications, 10(1), 3043. https://doi.org/10.1038/s41467-019-11039-6
10. Toriello, H. V., Meck, J. M., & Professional Practice and Guidelines Committee (2008). Statement on guidance for genetic counseling in advanced paternal age. Genetics in medicine : official journal of the American College of Medical Genetics, 10(6), 457–460. https://doi.org/10.1097/GIM.0b013e318176fabb</sup>

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