The American College of Obstetricians and Gynecologists (ACOG) has issued recommendations for expanded carrier screening for genetic disorders in all women during and before pregnancy, as published in Obstetrics & Gynecology.
The guidelines recommend that each healthcare provider should establish a standard approach for ethnic-specific, pan-ethnic, or expanded carrier screening. In addition to screening women for cystic fibrosis, clinicians are also advised to offer screening for all women for spinal muscular atrophy (SMA) and to conduct a complete blood count to assess for the risk of hemoglobinopathy.
The guidelines, issued in two separate Committee Opinion statements, also recommend expanded carrier screening, which tests for as many as several hundred conditions simultaneously, as an acceptable strategy for prenatal carrier screening. Screened conditions should be able to be diagnosed prenatally and have potential opportunities for antenatal intervention to improve perinatal outcomes, changes to delivery management to optimize newborn and infant outcomes, and parental education about special care needs after birth. Screening may also be indicated based on family history or ethnicity.
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According to the committee, screening before pregnancy is preferable because it offers the most complete range of reproductive options, and increased knowledge of potential genetic outcomes allows individuals to make informed decisions and plans around pregnancy based on personal values.
A summary of ACOG’s recommendations is as follows:
- Ethnic-specific, pan-ethnic, and expanded carrier screening are acceptable strategies for pre-pregnancy and prenatal carrier screening. Each obstetrician–gynecologist or other healthcare provider or practice should establish a standard approach that is consistently offered to and discussed with each patient, ideally before pregnancy. After counseling, a patient may decline any or all carrier screening.
- If a patient requests a screening strategy other than the one used by the obstetrician–gynecologist or other healthcare provider, the requested test should be made available to her after counseling on its limitations, benefits, and alternatives.
- All patients who are considering pregnancy or are already pregnant, regardless of screening strategy and ethnicity, should be offered carrier screening for cystic fibrosis and spinal muscular atrophy, as well as a complete blood count and screening for thalassemias and hemoglobinopathies. Fragile X premutation carrier screening is recommended for women with a family history of fragile X–related disorders or intellectual disability suggestive of fragile X syndrome, or women with a personal history of ovarian insufficiency. Additional screening also may be indicated based on family history or specific ethnicity.
- Couples with consanguinity should be offered genetic counseling to discuss the increased risk of recessive conditions being expressed in their offspring and the limitations and benefits of carrier screening.
- Carrier screening will not identify all individuals who are at risk of the screened conditions. Patients should be counseled regarding residual risk with any test result.
- Prenatal carrier screening does not replace newborn screening, nor does newborn screening diminish the potential benefit of prenatal carrier screening.
- If a woman is found to be a carrier for a specific condition, her reproductive partner should be offered screening to provide accurate genetic counseling for the couple with regard to the risk of having an affected child. Additional genetic counseling should be provided to discuss the specific condition, residual risk, and options for prenatal testing.
- If a carrier couple (ie, carriers for the same condition) is identified before pregnancy, genetic counseling is encouraged so that reproductive options (eg, donor gametes, pre-implantation genetic diagnosis, prenatal diagnosis) can be discussed.
- Individuals with a family history of a genetic disorder may benefit from the identification of the specific familial mutation or mutations rather than carrier screening. Knowledge of the specific familial mutation may allow for more specific and rapid prenatal diagnosis.
- Given the multitude of conditions that can be included in expanded carrier screening panels, the disorders selected for inclusion should meet several of the following consensus-determined criteria: have a carrier frequency of 1 in 100 or greater, have a well-defined phenotype, have a detrimental effect on quality of life, cause cognitive or physical impairment, require surgical or medical intervention, or have an onset early in life. In addition, screened conditions should be able to be diagnosed prenatally and may afford opportunities for antenatal intervention to improve perinatal outcomes, changes to delivery management to optimize newborn and infant outcomes, and education of the parents about special care needs after birth.
- Carrier screening panels should not include conditions primarily associated with a disease of adult onset.
ACOG notes that these recommendations are not a substitute for other important routine testing, including newborn screening, and they do not identify all individuals who are at risk of a condition.
References
- Committee Opinion No. 690 Summary: Carrier Screening in the Age of Genomic Medicine. Obstet Gynecol. March 2017. doi: 10.1097/AOG.0000000000001947
- Committee Opinion No. 691: Carrier Screening for Genetic Conditions. Obstet Gynecol. March 2017. doi: 10.1097/AOG.0000000000001952
