What additional test is recommended for a 40-year-old gravida 2 para 1 (G2P1) woman at 10 weeks gestation with no chronic medical conditions, normal blood pressure (euglycemia and normotension), and a normal physical examination, aside from routine prenatal laboratory testing?

From the Guidelines

For this 40-year-old pregnant woman at 10 weeks gestation, cell-free DNA screening (also known as non-invasive prenatal testing or NIPT) is recommended. This blood test analyzes fragments of fetal DNA in the maternal circulation to screen for common chromosomal abnormalities such as trisomy 21 (Down syndrome), trisomy 18, and trisomy 13. Cell-free DNA screening is particularly recommended for women of advanced maternal age (35 years or older), as this patient is 40 years old, which significantly increases her risk for fetal chromosomal abnormalities 1. The test can be performed as early as 10 weeks gestation, making it appropriate at this visit.

Key Points to Consider

• The patient's age is a significant risk factor for fetal chromosomal abnormalities, making screening crucial 1.
• Cell-free DNA screening has high sensitivity and specificity for detecting common chromosomal abnormalities 1.
• While this screening test is highly effective, positive results would require confirmation with diagnostic testing such as amniocentesis or chorionic villus sampling.
• The patient should be counseled that this is a screening test, not a diagnostic test, and that it primarily focuses on the most common chromosomal abnormalities but does not detect all genetic conditions or structural abnormalities.

Recommendations

• Cell-free DNA screening should be offered to this patient due to her advanced maternal age and the presence of a singleton pregnancy, which increases the accuracy of the screening test 1.
• The patient should be informed about the benefits and limitations of cell-free DNA screening, including its high sensitivity and specificity for common chromosomal abnormalities, and the need for confirmatory diagnostic testing if the screening result is positive.

From the Research

Recommended Tests for Prenatal Care

In addition to routine prenatal laboratory testing, the following tests are recommended for this patient:

• Non-invasive prenatal testing (NIPT) 2, 3, 4, 5, 6

Rationale for NIPT

The patient is at 10 weeks gestation and has no chronic medical conditions or prior surgeries, but NIPT is still recommended due to its ability to detect fetal chromosomal abnormalities, such as trisomy 21,18, and 13 2, 3, 4, 5.

Benefits of NIPT

NIPT has several benefits, including:

• High detection rate for fetal chromosomal abnormalities 3, 5
• Low false-positive rate for trisomy 21 5
• Ability to detect other chromosomal abnormalities, such as sex chromosome abnormalities and autosomal abnormalities 3, 5
• Non-invasive, reducing the risk of miscarriage associated with invasive testing 4, 6

Limitations of NIPT

While NIPT is a valuable tool for prenatal screening, it is not without limitations:

• False-positive results can occur, particularly for rarer chromosomal abnormalities 3, 5
• NIPT is not diagnostic, and positive results must be confirmed with invasive testing 4, 6
• NIPT may not detect all types of chromosomal abnormalities, such as triploidy 5