Genetic screening test timeline by trimester

How do the options compare?

The comparison below weighs mainstream OB guideline standing, the depth of the pregnancy evidence base, dosing clarity, expected onset, and interactions worth flagging to your provider.

• ACOG describes first-trimester screening at about 10 to 13 weeks, the quad screen at 15 to 22 weeks, and the anatomy ultrasound at 18 to 22 weeks. The quad screen assesses the chance of trisomy 21, trisomy 18, and neural tube defects. 1
• Updated SMFM guidance identifies cell-free DNA as the most sensitive and specific screening test for common trisomies 21, 18, and 13. Sex-chromosome screening is an opt-in choice after counseling, and routine population screening for microdeletions is not recommended. 2
• Chorionic villus sampling is a diagnostic test performed between 10 and 13 weeks; a more recent cohort study found pregnancy loss rates after CVS comparable to pregnancies that did not have the procedure. 3
• Amniocentesis, a diagnostic test that samples amniotic fluid, can be performed from 15 weeks of gestation onward, with an attributable pregnancy loss risk of about 0.13 percent in experienced hands. 4
• NIPT is a screening test, not a diagnostic one, so a higher-chance result should be confirmed with CVS or amniocentesis before any decision is made; one UK hospital review found roughly a quarter of higher-chance NIPT results for trisomy 21, 18, or 13 did not hold up on diagnostic testing. 5

Which option makes sense?

The options above differ in their evidence, limitations, and suitability. Inclusion in this comparison is not a recommendation. Please consult your healthcare provider before making a decision based on these findings.

Disclosure: Pregnancy Smart makes pregnancy supplements, though not in this category. This comparison is a plain description of the pregnancy evidence, not a sales page.