Is pre-pregnancy genetic screening recommended?

Pre-Pregnancy Genetic Screening Recommendation

Yes, pre-pregnancy carrier screening should be offered to all women planning conception, as this timing provides the widest range of reproductive options including preimplantation genetic diagnosis, donor gametes, or adoption—options that become unavailable or significantly more complicated once pregnancy is established. 1

Why Pre-Pregnancy Screening Is Preferred Over Prenatal Screening

The critical distinction here is between carrier screening (which should occur pre-pregnancy) versus aneuploidy screening (which occurs during pregnancy). 1

Carrier Screening Should Occur Pre-Pregnancy

• The woman should undergo carrier screening first, ideally before conception, as recommended by the American College of Medical Genetics. 1
• Pre-pregnancy carrier screening allows couples to consider all reproductive options including preimplantation genetic diagnosis, use of donor gametes, or adoption—choices that are only available before natural conception occurs. 1
• A sequential testing approach is most cost-effective: if the woman tests positive as a carrier for an autosomal recessive disorder, then the male partner should be offered carrier testing to assess offspring risk. 1
• Carrier screening should be based on ethnic background, family history, and consanguinity assessment. 1

What Pre-Pregnancy Screening Detects

• The primary preconception focus should be on carrier screening for autosomal recessive and X-linked disorders rather than age-related chromosomal risks (like Down syndrome), which are typically addressed through prenatal screening once pregnancy is established. 1
• Examples include cystic fibrosis, sickle cell disease, Tay-Sachs disease, and other conditions based on ethnicity and family history. 1

Aneuploidy Screening Occurs During Pregnancy, Not Before

• Screening for chromosomal abnormalities like trisomy 21 (Down syndrome) cannot be performed pre-pregnancy because these conditions arise during conception and are not inherited carrier states. 2
• All pregnant women should be offered aneuploidy screening or diagnostic testing regardless of age, but this occurs after pregnancy is established. 2, 3
• Options during pregnancy include first-trimester screening, cell-free DNA (cfDNA) screening, or diagnostic testing with CVS or amniocentesis. 2

Critical Timing Considerations

If Pre-Pregnancy Screening Cannot Be Completed

• If carrier screening cannot be completed before conception, it should be initiated as early as possible in pregnancy. 1
• If the woman is tested after 14 weeks gestation, both partners should be tested concurrently rather than sequentially due to time constraints for decision-making. 1

The Sequential Approach Is Safer and More Cost-Effective

• Testing the woman first, then the male partner only if needed, is safer and more cost-effective than proceeding directly to invasive prenatal procedures like CVS or amniocentesis if carrier status is unknown. 1

Common Pitfall to Avoid

Do not wait until pregnancy is established to initiate carrier screening discussions. 1 The preconception period provides the widest range of reproductive options and avoids the time pressure and emotional stress of making decisions during an ongoing pregnancy. 1 Once pregnant, couples lose the option of preimplantation genetic diagnosis and face more difficult decisions if both partners are found to be carriers of the same autosomal recessive condition. 1

Additional Preconception Counseling

Beyond genetic carrier screening, comprehensive preconception counseling should include folic acid supplementation (400-800 mcg daily), medical history review, medication review for teratogenic drugs, infection screening (rubella immunity, HIV, hepatitis), and lifestyle modifications (smoking cessation, alcohol avoidance, weight optimization). 1

Summary Algorithm

For a woman planning pregnancy:

1. Offer carrier screening based on ethnicity, family history, and consanguinity before conception 1
2. If woman tests positive as carrier, test male partner for same condition 1
3. If both are carriers, discuss reproductive options including PGD, donor gametes, adoption, or prenatal diagnosis 1
4. Once pregnant, offer aneuploidy screening (first-trimester screen, cfDNA, or diagnostic testing) 2