Prenatal Screening And Diagnostic Testing Options For Chromosome Aneuploidy

Publication Date: November 1, 2012
Last Updated: March 14, 2022

Recommendations for all patients

Providers should offer the options of maternal serum screening (MSS) and diagnostic testing for chromosome aneuploidy to every patient.

  • Providers should engage in a discussion with their patients about the benefits, limitations, and risks of MSS and diagnostic testing so that patients may make informed and autonomous decisions.

  • If the provider feels a patient would benefit from additional discussion prior to making a decision, a referral to a genetic counselor or other qualified provider may be appropriate.

  • Documentation of the patient's decision to elect or to decline screening and testing should be made in the patient's medical record.

  • Providers should be aware of factors that may impact the options available to their patients, such as the patient's gestational age, insurance coverage and access to services and providers.

An ultrasound to assess the fetal anatomy is suggested at approximately 18w0d‐20w0d gestation for all patients regardless of whether or not they choose to have screening or diagnostic testing.

Recommendations for low risk patients less than 14 weeks of gestation:

For patients who may consider CVS or amniocentesis, stepwise sequential screening or combined first trimester screening should be considered because:

Both are tailored to fit the needs of patients who desire early detection of chromosome aneuploidy but wish to employ a screening method prior to making a decision about diagnostic testing.
Both allow for the option of CVS in higher risk pregnancies while deferring testing of lower risk pregnancies to the second trimester without causing increased anxiety.
Of the screening options that provide risk information in the first trimester, stepwise sequential screening has the highest detection rates for Down syndrome and trisomy 18.
If CVS is not an option, integrated screening may be considered in order to maximize detection rates.
If a patient completes combined first trimester screening, a separate second trimester MSS for chromosome aneuploidy is NOT indicated. Screening for chromosome aneuploidy in the second trimester in patients who present prior to 14 weeks should ONLY be performed as a part of integrated, serum integrated, stepwise sequential, or contingency screening. Independent screening in first and second trimesters increases the false positive rate of screening.
Patients who have an increased NT (≥ 95th % or ≥ 3.0mm) should be offered diagnostic testing by either CVS or amniocentesis. A referral for a fetal echocardiogram should also be considered if the NT ≥3.5mm.
Early amniocentesis (prior to 15 weeks of gestation) is not recommended due to the increased risks for pregnancy loss, clubfoot, and fluid leakage. CVS should be offered as the diagnostic testing option for chromosome aneuploidy in the first trimester.

Recommendations for low risk patients after 14 weeks of gestation:

Patients who desire MSS but did not have MSS in the first trimester should be offered a quad or penta screen rather than a triple screen due to the increased detection rates.
Amniocentesis should be offered as the diagnostic testing option for chromosome aneuploidy for patients after 15 weeks of gestation.

Recommendations for patients at increased risk for chromosome aneuploidy

Patients who desire screening information may be offered NIPT due to the high detection rates and low false positive rates. NIPT should only be offered in the context of informed consent, education, and counseling by a qualified provider, such as a genetic counselor. Standard confirmatory diagnostic testing should be offered as follow‐up to positive NIPT results. High risk patients who decline NIPT but remain interested in screening should be made aware of alternate screening options as appropriate based on gestational age and screening availability.
If the patient presents prior to 14 weeks gestation, CVS and amniocentesis should both be offered as diagnostic testing options for chromosome aneuploidy.
If the patient presents after 14 weeks gestation, amniocentesis should be offered as the diagnostic testing option for chromosome aneuploidy.

Recommendation Grading




Prenatal Screening And Diagnostic Testing Options For Chromosome Aneuploidy

Authoring Organization

Publication Month/Year

November 1, 2012

Last Updated Month/Year

January 11, 2023

Document Type


External Publication Status


Country of Publication


Document Objectives

To provide information that assists physicians and allied health professionals in making decisions about different screening and diagnostic testing for chromosome aneuploidy throughout pregnancy.

Target Patient Population

Pregnancy patients

Inclusion Criteria

Female, Adult

Health Care Settings

Ambulatory, Hospital, Laboratory services, Outpatient

Intended Users

Nurse, nurse practitioner, physician, physician assistant


Counseling, Assessment and screening, Diagnosis

Diseases/Conditions (MeSH)

D005820 - Genetic Testing, D000782 - Aneuploidy, D025063 - Chromosome Disorders, D011295 - Prenatal Care, D011296 - Prenatal Diagnosis


prenatal care, prenatal diagnosis, aneuploidy