Table of contents
Prenatal screening for chromosomal abnormalities
What's new
Updated 2024 SOGC guidelines for prenatal screening for fetal chromosomal anomalies.
Guidelines
Key sources
The following summarized guidelines for the evaluation and management of prenatal screening for chromosomal abnormalities are prepared by our editorial team based on guidelines from the Society of Obstetricians and Gynaecologists of Canada (SOGC 2024,2020,2017), the American College of Medical Genetics (ACMG 2022), the American College of Obstetricians and Gynecologists (ACOG 2021), the American College of Obstetricians and Gynecologists (ACOG/SMFM ...
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Screening and diagnosis
Indications for screening, general principles: as per SOGC 2024 guidelines, offer prenatal screening for the most common fetal aneuploidies and major fetal anomalies to all pregnant individuals, regardless of age, through informed counseling and shared decision-making.
A
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Indications for screening (trisomies)
Indications for screening (deletions)
Indications for screening (sex chromosome aneuploidies)
Choice of screening test (general principles)
Choice of screening test (first-trimester ultrasound)
Choice of screening test (mid-trimester ultrasound)
Choice of screening test (maternal serum screening)
Choice of screening test (cell-free DNA)
Choice of screening test (amniocentesis, general population)
Choice of screening test (amniocentesis, at-risk population)
Diagnostic investigations
Further evaluation
As per SOGC 2024 guidelines:
Offer genetic counseling and invasive diagnostic testing if a fetal structural abnormality, not a soft marker, is identified during the first- or second-trimester ultrasound, regardless of previous screening test results. Include rapid aneuploidy detection and reflex microarray analysis or exome/genome sequencing if rapid aneuploidy detection is normal or inconclusive, recognizing that the diagnostic role of fetal exome/genome sequencing is a rapidly evolving area.
A
Do not use the presence of an isolated fetal soft marker in the second trimester to adjust the a priori risk for aneuploidy in patients at low risk based on previous screening.
D
Specific circumstances
Patients undergoing assisted reproductive technologies: as per ACOG/SMFM 2020 guidelines, offer prenatal screening and prenatal diagnosis in all patients undergoing ART regardless of previous preimplantation genetic testing because preimplantation genetic testing is not uniformly accurate.
B
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Patients with twin pregnancies
Patients with multifetal gestation