Why didn't it work? The honest reasons an IVF cycle can fail

A negative test after everything IVF asks of you is one of the hardest moments in medicine, and it usually comes with no explanation. This page sets out the reasons cycles fail, in roughly the order of how common they are — not to give you your answer, which only your clinic can attempt, but so the conversation you have with them starts from solid ground.

1. The embryo could not continue (the commonest reason)

Most embryos, from anyone, at any age, carry a chromosomal error that means they cannot develop into a pregnancy — or start one and miscarry. The share rises with age: roughly a third of blastocysts at 30, more than half by 38, most by 42. These embryos usually look normal under the microscope. This single fact explains the majority of failed transfers, and it is nobody's fault and no lab's failing.

What can be learned: whether genetic testing of embryos (PGT-A) would help you avoid transferring embryos that can't succeed — useful for some, not all. PGT-A explained →

2. Not enough usable embryos

Few eggs, few mature, low fertilisation, or few reaching blastocyst. Each is a different problem with a different fix — stimulation protocol, trigger timing, insemination method, or simply age.

What can be learned: look at where your numbers fell compared with the usual funnel. Why the numbers go down →

3. The lining or the timing

Occasionally the uterus isn't receptive — the lining too thin, fluid in the cavity, a polyp or fibroid, an infection or inflammation, or the transfer out of step with the "window" of receptivity. These are the reasons that are most often fixable.

What can be learned: a hysteroscopy or scan review; sometimes an endometrial receptivity test after repeated failure, though its value is debated.

4. Difficult transfer or technical factors

A very difficult catheter passage, bleeding, or an embryo retained in the catheter can lower chances for that transfer. Rare, and clinics record when it happens.

5. Sperm and egg quality beyond what a report shows

High sperm DNA fragmentation, or egg quality problems that grading can't see, can produce embryos that look fine and don't implant.

6. Whole-body factors

Uncontrolled thyroid disease, diabetes, very high or low weight, smoking, and some clotting or immune conditions can lower chances modestly. Many "immune" treatments sold for implantation failure have little evidence; ask what the evidence is before adding them.

And, honestly: chance

Even a genetically normal blastocyst in a receptive uterus implants only about six or seven times in ten. A failed transfer of a good embryo can be — and often is — simply the toss of a coin. That is why doctors talk about cumulative chances over more than one transfer.

What to ask at the follow-up

• At which step did my numbers differ from what you'd expect for my age and AMH?
• How did the embryo(s) look at transfer, and how did the transfer itself go?
• Is there anything about my lining or uterus worth checking before the next attempt?
• Would you change the protocol, the insemination method, or the day of transfer — and why?
• Would genetic testing help in my case, or mostly add cost?
• What does your lab's own data say about how embryos are doing generally right now? (A fair question. Good labs measure this monthly.)