Fetal Viability by Week When Is a Fetus Considered Viable?

By Dr. Kulsoom Baloch

Learn more about Dr. Baloch

Introduction

One of the most important milestones in pregnancy is fetal viability — the point at which a fetus can survive outside the womb with medical support. This guide explains what fetal viability is, how it’s measured, and when a fetus is typically considered viable by week.

What Does Fetal Viability Mean?

Fetal viability refers to the stage in pregnancy when the fetus is developed enough to survive outside the womb, typically with the help of a neonatal intensive care unit (NICU). This is not a fixed week but depends on multiple factors including organ maturity, birth weight, and medical support available.

Viability by Gestational Week

• Before 22 weeks: Survival is extremely rare.
• 22–23 weeks: Considered the borderline of viability; survival rates range from 10–35% with advanced NICU care.
• 24 weeks: Survival increases to about 50–60%.
• 25–26 weeks: Around 75–80% of babies survive.
• 27+ weeks: Viability is high, with more than 90% survival by 28 weeks.

Key Factors Influencing Fetal Viability

• Gestational age – The most important factor.
• Birth weight – Higher weight correlates with better survival.
• Lung development – Critical for breathing outside the womb.
• Access to NICU care – Life-saving technology dramatically improves survival.

Medical Tools Used to Assess Viability

• Ultrasound – To monitor fetal growth and amniotic fluid.
• Non-Stress Tests (NST) – To evaluate fetal heart rate and movement.
• Biophysical Profile (BPP)– Combines ultrasound and NST to assess health.

Legal and Ethical Considerations

In some regions, fetal viability affects legal definitions of life and abortion laws. It’s important to understand that viability is a medical concept, but also influences ethical and legal decisions in reproductive care.

Fetal Viability and Surrogacy

In surrogacy journeys, viability plays a key role in determining safe delivery timing and managing any complications in the third trimester. Surrogacy teams work closely with OB/GYNs to track fetal development week by week.

Common Questions

• Can a baby survive at 23 weeks?: With advanced care, some do, but risks are high.
• What is the age of viability in the U.S.?: Medically, it’s often set at 24 weeks.
• Does viability mean a baby will be healthy?: Not always; long-term outcomes vary.

Conclusion

Fetal viability is a moving target influenced by technology, medicine, and individual circumstances. Knowing when a fetus is considered viable can help parents make informed decisions during high-risk pregnancies or fertility journeys. At Surrogacy4All, we ensure both intended parents and surrogates receive expert care throughout the pregnancy.