IVF Success Rate: How Likely Is Pregnancy with In‑Vitro Fertilisation?

Quick Takeaways

• Average live‑birth rate per IVF cycle in the UK is about 27% for women under 35.
• Maternal age is the single biggest predictor - rates drop to 8% after 42.
• Using fresh embryos, ICSI, or pre‑implantation genetic testing can shift odds by a few points.
• Clinic‑specific data matters; look for cumulative live‑birth rates over multiple cycles.
• Lifestyle tweaks (BMI, smoking, stress) can improve your chances by up to 5%.

What Exactly Is IVF?

When people talk about the IVF success rate, they are really asking how often a full IVF cycle ends in a live birth. In vitro fertilisation (IVF) is a medical procedure that combines eggs and sperm outside the body, creates embryos, and then transfers one or more of those embryos into the uterus. It’s the most common assisted reproductive technology (ART) worldwide and the benchmark against which other techniques are measured.

How Success Is Measured

There are three numbers you’ll see on clinic websites and in HFEA reports:

1. Clinical pregnancy rate - the chance that a gestational sac is seen on ultrasound.
2. Live‑birth rate - the chance that a baby is born alive after 24 weeks. This is the gold standard because many early pregnancies end in miscarriage.
3. Cumulative live‑birth rate - the chance of a live birth after using all fresh and frozen embryos from a single egg retrieval.

Most patients focus on the live‑birth rate because it reflects the final outcome they care about.

The Age Factor: Why It Dominates Success

Age changes the odds dramatically. The UK Human Fertilisation and Embryology Authority (HFEA) publishes age‑group data every year. Below is a snapshot from the 2024 report:

Notice how the cumulative figure (including frozen embryos) is always higher - many clinics freeze surplus embryos and give patients another chance without a new egg retrieval.

Key Factors That Shift the Odds

Beyond age, several variables can either boost or lower your chances. Understanding them helps you set realistic expectations and, where possible, optimise your treatment.

• Ovarian stimulation protocol - Higher egg numbers usually improve cumulative success, but aggressive stimulation can affect egg quality.
• Embryo quality - Graded by morphology and, increasingly, by genetic testing (PGT‑A for aneuploidy). Transfer of a euploid blastocyst lifts live‑birth rates by 10‑15 %.
• ICSI (intracytoplasmic sperm injection) - Primarily used for male factor infertility; its impact on overall success is neutral when sperm are normal.
• Body mass index (BMI) - Under 20 or over 30 can reduce live‑birth rates by 5‑10 % because of hormonal imbalance and endometrial receptivity.
• Smoking - Active smokers have a 20 % lower chance of implantation; quitting 3 months before treatment is advisable.
• Uterine environment - Fibroids, adenomyosis, or thin endometrium (<7 mm) can cut success in half unless corrected.

Some of these factors are within your control (weight, smoking, stress management), so discussing them with your specialist can meaningfully improve odds.

Clinic‑Specific Success: What Numbers to Trust

Not all clinics report the same metrics. Here’s a quick checklist for evaluating a clinic’s data:

1. Do they publish cumulative live‑birth rates per age group?
2. Are the figures based on all cycles performed, not just the “best” ones?
3. Is the data independent (e.g., verified by the HFEA) or self‑reported?
4. Do they break out fresh vs. frozen embryo results?
5. Do they disclose how many cycles each patient completed on average?

When you line up two clinics, the one with higher cumulative rates for your age bracket is usually the safer bet, assuming comparable safety records.

Putting the Numbers Into Context

Let’s say you’re a 36‑year‑old with a BMI of 28, non‑smoker, and your partner has normal sperm. The HFEA data suggests a fresh‑cycle live‑birth rate of ~22 %. Adding PGT‑A to select a euploid blastocyst could lift that to roughly 30 %. If the clinic also freezes surplus embryos, your cumulative chance after two attempts might be around 45 %.

Contrast that with a 43‑year‑old with a BMI of 32 who smokes. Fresh‑cycle rates drop to ~8 %, and even with PGT‑A you might only reach 12 %. Lifestyle changes could push the odds up a couple of points, but overall expectations need to be tempered.

Frequently Asked Questions

Bottom Line

Pregnancy odds with IVF are not a single number - they depend on age, embryo quality, clinic performance, and personal health choices. By looking at cumulative live‑birth rates, understanding how each factor nudges the odds, and picking a transparent clinic, you can turn vague statistics into a concrete plan.