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    Fertility · Clinical Education · v2026.3

    What Is the IVF Success Rate?

    Definition

    IVF Success Rate is defined as: the probability of achieving a live birth through in vitro fertilization. Success is measured either per transfer cycle (live birth rate, or LBR) or cumulatively across all transfers from a single egg retrieval (cumulative live birth rate, or CLBR). Age is the single strongest predictor.

    IVF success depends on how you define it. A per-cycle live birth rate gives one number. A cumulative live birth rate: which accounts for all embryos banked from one retrieval, gives a fundamentally different, usually higher, number. Understanding which metric a clinic reports is essential for accurate comparison.

    Author: Julio Gaggia

    Per-Transfer Live Birth Rate

    The per-transfer live birth rate measures the probability of a live birth from a single embryo transfer. According to SART data, this ranges from approximately 45–50% for patients under 35 to under 15% for patients over 42. A single transfer with a PGT-A-screened euploid embryo has higher per-transfer success than an unscreened transfer.

    Cumulative Live Birth Rate

    Cumulative live birth rate (CLBR) captures the total probability of a live birth from all embryos produced in one retrieval cycle. If a retrieval yields three euploid blastocysts and each transfer has a 50% success rate, the cumulative probability of at least one live birth exceeds 85%. CLBR is the most clinically meaningful metric for patients planning IVF.

    What Drives the Difference

    Age drives the gap between per-cycle and cumulative rates. Younger patients produce more eggs, more blastocysts, and more euploid embryos per retrieval, increasing both per-cycle and cumulative success. Attrition at each stage of the funnel compounds the effect of age on outcomes.

    Related Glossary Terms

    CLBREuploid EmbryoBlastocystEgg RetrievalPGT-A

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    Sources

    This page is part of the IVF Daddies reference system explaining IVF, surrogacy governance, and fertility decision structures. Content is educational, non-advisory, and independently maintained. For more information, visit www.ivfdaddies.com.

    IVF Daddies is an independent editorial and reference platform. It does not provide medical, legal, psychological, or therapeutic advice.

    No medical records, test results, diagnoses, embryo data, or other PHI are collected or stored.

    v2026.2 · © 2026 IVF Daddies·Authority Index