Improving Inequities in Prenatal Screening: Time to Modernize Guidelines

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Professional guidelines can have a profound impact on reproductive health. In many cases, prenatal genetic screening is often only recommended for specific groups or individuals who have been historically recognized as high risk. Unfortunately, this approach results in missed opportunities to identify people who have an equal or greater risk, which results in a disparity in how prenatal genetic screening is conducted both preconceptionally and prenatally. Current guidelines for both carrier screening for serious inherited conditions and noninvasive prenatal screening for chromosomal abnormalities in the fetus are examples of prenatal screening that exacerbate inequities.

Carrier screening guidelines are typically ethnicity-based. Many individuals are only screened for cystic fibrosis and spinal muscular atrophy, even though they may be at risk for more than these two conditions. Multiple studies have demonstrated that ethnicity-based carrier screening fails to identify carriers and at-risk couples effectively. In one study of nearly 350,000 individuals across ethnicities, guidelines-based screening identified only 6% of affected conceptuses among East Asians, 21% among Hispanics, 35% among Northern Europeans, and 45% among Ashkenazi Jewish individuals. This inequity occurs for several reasons:

  1. Ethnicity is often unknown or inaccurate. We know that about 40% of adults cannot  identify the ancestry of all four of their biological grandparents.
  2. The U.S. population has become more ethnically mixed over the last few decades. One in six marriages now occur between people of different ethnicities, and one in seven infants are multi-ethnic.
  3. Studies have shown that most carriers are not in the ethnic populations for which guidelines exist.

Carrier screening offered pan-ethnically, that is, without regard to ethnicity, more effectively identifies at-risk couples than ethnicity-based screening.

Noninvasive prenatal screening (NIPS) assesses the risk of the fetus being affected by chromosomal abnormalities like trisomy 21, 18, and 13. Guidelines recommend against offering NIPS to those who are significantly obese (BMI >30) and recommend against reporting results (a “test failure”) when fetal fraction, that is, the amount of fetal DNA in the mother’s blood, is below 4%. Instead, it is recommended that these women receive traditional serum-based screening, which is far less accurate than NIPS in predicting the risk of chromosomal abnormalities. Significant obesity occurs in ~50%, 45%, and 35% of pregnant women who are Native American, African American, and Hispanic, respectively. According to guidelines, these women should be offered the less accurate aneuploidy screening test than those with a BMI <30, creating a disparity based on both body size and ethnicity. Other studies have shown that maternal ethnicity is independently associated with low fetal fraction; those of African American and South Asian ethnicities were nearly twice as likely to experience test failures than those of other ethnicities. Test failures delay results and translate to fewer pregnancy management options, disproportionately impacting certain racial and ethnic groups. Despite the emergence of NIPS technology that provides accurate results at low fetal fraction, guidelines have yet to be updated, creating ethnic disparities in access to NIPS. 

Current prenatal screening guidelines disproportionately limit access to care for individuals of certain ethnicities. Evidence supports the modernization of guidelines to improve equitable care. Midwives can play a role in improving access to prenatal genetic screening by advocating for updated guidelines. Learn more about this topic in our session at the ACNM 66th Annual Meeting, held virtually May 23 – 25, 2021.

Authors

Edith Smith, DNP, CNM, WHNP-BC, AGN-BC

Summer Pierson, MS, CGC