Washington, DC – In recognition of how critical genetic testing is in preparing for and managing a successful pregnancy, The American College of Obstetricians and Gynecologists (ACOG) has expanded guidelines on carrier screening in two new Committee Opinions released today.
In the past, ACOG recommended carrier screening—genetic testing that determines whether an asymptomatic person has a genetic mutation or abnormalities associated with a particular disorder that may be passed on to children—based primarily on ethnicity. The focus was on specific ethnic populations with known increased risk for particular disorders. ACOG’s two new Committee Opinions go beyond previous guidance to broaden who should be screened and for which genetic disorders.
The new guidance recommends each provider or practice establish a standard approach for ethnic-specific, pan-ethnic—meaning all women—or expanded carrier screening. In addition to existing guidance recommending universal screening for cystic fibrosis, all women should also be offered screening for spinal muscular atrophy (SMA), as well as a complete blood count to assess risk of hemoglobinopathy.
“Genetic conditions, including SMA, are not limited to one ethnic group. And certain conditions are common enough that it’s essential offer screening for them in every patient,” said Committee Opinion author Joseph R. Biggio Jr., MD, director of the Division of Maternal Fetal Medicine at the University of Alabama at Birmingham. “A growing number of Americans are also of mixed or uncertain ethnic backgrounds, which means we may not identify some people who are at risk of passing genetic conditions to their children when we follow ethnic-based recommendations.”
The updated guidance also discusses expanded carrier screening, which tests for up to several hundred conditions simultaneously, as an acceptable strategy for prenatal carrier screening. Conditions included in an expanded carrier screening panel should meet the following criteria: have a carrier frequency of one 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, and have an onset early in life. Additionally, 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. Committee Opinion No. 691 offers further recommendations for individual disorders.
Every ob-gyn or other health care provider should establish a standard approach to carrier screening that’s consistently discussed with each patient and takes into account a patient’s family history and personal values. While screening for a particular condition should generally be performed only once in a person’s lifetime, patients can opt to decline any or all carrier screening.
If a woman is found to be a carrier for a specific condition, her reproductive partner should be offered screening. If both partners are found to be carriers, genetic counseling should be offered. Because relatives are also at risk of carrying the same mutation, the patient should be encouraged to inform them of the risk and the availability of testing.
Information about carrier screening should be provided to all women who are pregnant, but ideally should be provided to women even as they are considering pregnancy. Screening before pregnancy is preferable as it offers the most complete range of reproductive options. Increased knowledge of potential genetic outcomes allows individuals to make informed decisions and plans around pregnancy based on personal values.
The Committee Opinions underscore the importance of reviewing carrier screening results with patients carefully. Biggio said, “Patients must have a clear understanding of what their results mean in order to feel empowered and enabled to make informed decisions about their reproductive health or to prepare to care for future children. In some instances, this may include referring patients to genetic specialists to ensure they receive education and care tailored to their carrier screening results.”
Although there are many benefits to carrier screening, the Committee Opinions note that it is not a substitute for other important routine testing, including newborn screening, and it does not identify all individuals who are at risk of a condition.
Additional resources for providers and patients are available at acog.org/CarrierScreening.
The Committee Opinions, “Carrier Screening in the Age of Genomic Medicine,” #690, and “Carrier Screening for Genetic Conditions,” #691, will be available in the March 2017 issue of Obstetrics and Gynecology.
Other recommendations issued in the March Obstetrics & Gynecology:
Committee Opinion #688, Management of Suboptimally Dated Pregnancies
The American College of Obstetricians and Gynecologists considers first-trimester ultrasonography to be the most accurate method to establish or confirm gestational age. Pregnancies without an ultrasonographic examination confirming or revising the estimated due date before 22 0/7 weeks of gestation should be considered suboptimally dated. This document provides guidance for managing pregnancies in which the best clinical estimate of gestational age is suboptimal. There is no role for elective delivery in a woman with a suboptimally dated pregnancy. Although guidelines for indicated late-preterm and early-term deliveries depend on accurate determination of gestational age, women with suboptimally dated pregnancies should be managed according to these same guidelines because of the lack of a superior alternative. The best clinical estimate of gestational age should serve as the basis for decisions regarding antenatal corticosteroid exposure in women with suboptimally dated pregnancies who are at perceived risk of preterm delivery. Amniocentesis for fetal lung maturity is not recommended as a routine component of decision making when considering delivery in a woman with a suboptimally dated pregnancy. Late-term delivery is indicated at 41 weeks of gestation when gestational age is uncertain, using the best clinical estimate of gestational age. Initiation of antepartum fetal surveillance at 39–40 weeks of gestation may be considered for suboptimally dated pregnancies. During the antenatal care of a woman with a suboptimally dated pregnancy, it is reasonable to consider an interval ultrasonographic assessment of fetal weight and gestational age 3–4 weeks after the initial ultrasonographic study.
Committee Opinion #689, Delivery of a Newborn with Meconium-Stained Amniotic Fluid
In 2006, the American Academy of Pediatrics and the American Heart Association published the 2005 guidelines on neonatal resuscitation. Before the 2005 guidelines, management of a newborn with meconium-stained amniotic fluid included suctioning of the oropharynx and nasopharynx on the perineum after the delivery of the head but before the delivery of the shoulders. The 2005 guidelines did not support this practice because routine intrapartum suctioning does not prevent or alter the course of meconium aspiration syndrome in vigorous newborns. However, the 2005 guidelines did support intubation of the trachea and suctioning of meconium or other aspirated material from beneath the glottis in nonvigorous newborns. In 2015, the guidelines were updated. Routine intubation and tracheal suctioning are no longer required. If the infant is vigorous with good respiratory effort and muscle tone, the infant may stay with the mother to receive the initial steps of newborn care. If the infant born through meconium-stained amniotic fluid presents with poor muscle tone and inadequate breathing efforts, the initial steps of resuscitation should be completed under the radiant warmer. Appropriate intervention to support ventilation and oxygenation should be initiated as indicated for each infant. Infants with meconium-stained amniotic fluid should no longer routinely receive intrapartum suctioning, whether they are vigorous or not. In addition, meconium-stained amniotic fluid is a condition that requires the notification and availability of an appropriately credentialed team with full resuscitation skills, including endotracheal intubation. Resuscitation should follow the same principles for infants with meconium-stained fluid as for those with clear fluid.