PGT-A Genetic Testing: Should You Test Your Embryos Before Transfer?

PGT-A (Preimplantation Genetic Testing for Aneuploidy) screens embryos for chromosomal abnormalities before transfer. It's one of the most debated topics in fertility treatment. Here's what you need to know to make an informed decision.

Key Takeaways

• What PGT-A tests: Screens embryos for the correct number of chromosomes (46) before transfer, detecting conditions like Down syndrome
• Success improvement: Euploid embryos have 60-70% implantation rates vs. 30-50% for untested embryos
• Cost in Portugal: Adds approximately €2,500-5,000 to your IVF cycle depending on number of embryos tested
• Best candidates: Women 38+, those with recurrent miscarriage or multiple failed transfers
• Important limitation: No proven improvement in cumulative live birth rates—you may reach success faster, but not necessarily more often

What Is PGT-A?

The Basics

PGT-A tests embryos for the correct number of chromosomes (46). Embryos with too many or too few chromosomes (aneuploid) are less likely to implant or may result in miscarriage.

Term	Meaning
Euploid	Normal chromosomes (46)—can be transferred
Aneuploid	Abnormal chromosomes—typically not transferred
Mosaic	Mix of normal and abnormal cells—may be transferred

What It Tests For

PGT-A screens all 23 pairs of chromosomes to detect:

• Missing chromosomes (monosomy)
• Extra chromosomes (trisomy)
• More complex abnormalities

Common abnormalities detected:

• Trisomy 21 (Down syndrome)
• Trisomy 18 (Edwards syndrome)
• Trisomy 13 (Patau syndrome)
• Sex chromosome abnormalities

What It Doesn't Test For

PGT-A does NOT detect:

• Single gene disorders (need PGT-M for that)
• Structural chromosome changes (need PGT-SR)
• All genetic conditions
• Future health problems

How PGT-A Works

The Process

Day 1-5: Embryos develop in the lab after fertilization

Day 5-6 (Blastocyst stage):

1. Embryologist removes 5-10 cells from the trophectoderm (outer layer that becomes placenta)
2. Cells are sent to genetics lab
3. Embryos are frozen while awaiting results

Days 7-14:

• Lab analyzes chromosomes
• Results returned to clinic
• Embryos classified as euploid, aneuploid, or mosaic

Next cycle:

• Euploid embryo thawed and transferred
• Frozen embryo transfer (FET) protocol followed

Timeline

Stage	When
Egg retrieval	Day 0
Fertilization	Day 1
Embryo development	Days 2-5
Biopsy	Day 5-6
Freezing	Day 5-6
Results	1-2 weeks later
Transfer	Next cycle (1-3 months)

Who Might Benefit from PGT-A?

Stronger Candidates

Situation	Why PGT-A May Help
Maternal age 38+	Higher aneuploidy rates
Recurrent miscarriage	May identify chromosomal causes
Multiple failed transfers	Screen out abnormal embryos
Previous aneuploid pregnancy	Higher recurrence risk
Desire for single embryo transfer	Confidence in embryo quality

Possible Candidates

Situation	Considerations
Age 35-37	Benefits less clear
First IVF cycle	May or may not improve outcomes
Few embryos expected	Risk of no embryos to transfer
Male factor infertility	Some evidence of benefit

May Not Benefit

Situation	Why
Under 35, first cycle	Low aneuploidy rates anyway
Only 1-2 embryos	Risk of losing all to testing
Financial constraints	High cost may not be justified

The Evidence: What Research Shows

Potential Benefits

Higher implantation rate per transfer:

• Euploid embryos: 60-70% implantation
• Untested embryos: 30-50% implantation

Reduced miscarriage risk:

• Euploid transfers: 10-15% miscarriage
• Untested transfers: 15-25% miscarriage

Shorter time to pregnancy:

• Fewer failed transfers
• More confident single embryo transfer

Limitations and Controversies

No proven improvement in cumulative live birth rate:

• Multiple studies show similar final outcomes
• You may reach success faster, but not more often

False results:

• 5-10% of embryos may be misdiagnosed
• Mosaic embryos are complex to interpret
• Some "abnormal" embryos could have resulted in healthy babies

Embryo loss:

• Some embryos damaged by biopsy
• Testing reduces the pool of transferable embryos

Costs

PGT-A Pricing in Portugal

Component	Cost
Biopsy procedure	€300-500 per embryo
Genetic analysis	€200-400 per embryo
Fixed testing fee	Some clinics charge €1,500-2,500 regardless of embryo number

Total Cost Scenarios

Embryos Tested	Approximate Cost
3 embryos	€1,500-2,500
5 embryos	€2,500-4,000
8 embryos	€3,500-5,000

Additional Costs to Consider

Item	Cost
Embryo freezing	€300-500
Annual storage	€200-350
FET cycle	€1,500-2,500

Total additional cost of PGT-A pathway: €3,500-6,000 beyond basic IVF

The Testing Decision: Questions to Ask

Questions for Your Clinic

1. What are my embryo's expected aneuploidy rates at my age?
2. How many embryos do you expect I'll have for testing?
3. What if all embryos test abnormal?
4. What's your policy on mosaic embryos?
5. How accurate is your lab's testing?

Questions for Yourself

1. How would I feel if all embryos test abnormal?
2. Can I afford the additional cost?
3. Am I prepared for the delay (frozen transfer required)?
4. How do I weigh the small risk of false results?
5. What does my clinic recommend for my situation?

Mosaic Embryos: The Gray Zone

What Are Mosaic Embryos?

Mosaic embryos have a mix of chromosomally normal and abnormal cells. They fall between euploid and aneuploid.

Classification	Meaning
Low-level mosaic	<40% abnormal cells—often transferable
High-level mosaic	>40% abnormal cells—approach with caution

Can Mosaic Embryos Result in Healthy Babies?

Yes. Many mosaic embryos:

• Self-correct during development
• Result in healthy pregnancies
• Should not be automatically discarded

Policy varies by clinic. Discuss their approach to mosaics before testing.

PGT-A vs. Other Testing

Comparison Table

Test	What It Screens	Who Needs It
PGT-A	Chromosome number (aneuploidy)	Optional for all
PGT-M	Specific genetic diseases	Carriers of known conditions
PGT-SR	Structural chromosome problems	Those with balanced translocations

When You Need PGT-M Instead

If you or your partner:

• Carry a known genetic condition (cystic fibrosis, sickle cell, etc.)
• Have family history of genetic disease
• Are both carriers of the same recessive condition

PGT-M is different from PGT-A and requires advance planning.

Making Your Decision

Arguments For PGT-A

• Reduces emotional toll of failed transfers and miscarriages
• Allows confident single embryo transfer
• May shorten time to successful pregnancy
• Provides information about embryo quality
• Peace of mind for some patients

Arguments Against PGT-A

• No proven improvement in final success rates
• Adds significant cost
• Small risk of false results
• Requires frozen transfer (delayed)
• May discard viable embryos
• Adds emotional complexity (dealing with results)

A Balanced Perspective

PGT-A is a tool, not a guarantee. It can help some patients—particularly older women or those with recurrent loss—but it's not universally beneficial and comes with real costs and limitations.

The best decision is the one that's right for your specific situation, values, and resources.

Questions to Discuss with Your Partner

• How would we feel about transferring an untested embryo?
• How would we cope if all embryos test abnormal?
• Can we afford the additional cost?
• Are we comfortable with the accuracy limitations?
• Does faster potential success outweigh the costs for us?

Frequently Asked Questions

Does PGT-A guarantee a healthy baby?

No. PGT-A screens for chromosome number only. It doesn't detect all genetic conditions or guarantee a healthy pregnancy.

What if all embryos test abnormal?

This is possible, especially with fewer embryos or advanced maternal age. You'd need to decide whether to do another retrieval cycle, transfer a mosaic, or explore other options.

Does the biopsy damage embryos?

When performed by skilled embryologists, the biopsy is safe. However, there's a small risk of damage. Survival rates are typically 95%+.

Can I do a fresh transfer with PGT-A?

No. Testing takes 1-2 weeks, so embryos must be frozen while awaiting results. All PGT-A pregnancies come from frozen embryo transfers.

Is PGT-A covered by insurance or NHS?

Rarely. PGT-A is usually an out-of-pocket expense. Some clinics in Portugal include it in packages at reduced rates.

What's the difference between PGS and PGT-A?

They're the same thing. PGS (preimplantation genetic screening) was renamed PGT-A for clarity.

Our Recommendation

There's no universal right answer. We suggest:

1. Discuss with your clinic based on your age, history, and expected embryo numbers
2. Understand the costs and limitations before deciding
3. Make a decision you're comfortable with—both testing and not testing are valid choices

Book a consultation to discuss whether PGT-A is right for your situation.

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Nestiva helps you understand your options and make informed decisions about your fertility treatment in Portugal.