IVF is well understood in outline by most people who are about to do it, and almost opaque in the details that actually matter during a cycle. The numbers, the protocol decisions, the jargon at results calls, these are the points where informed patients consistently say they wished they'd known more in advance.
Two main protocol types determine how stimulation is managed. The long protocol uses a GnRH agonist to down-regulate your own hormone production first, then stimulation starts from a suppressed baseline, this means the clinic controls timing more precisely. The antagonist protocol is now more commonly used: stimulation starts on day 2 of your period, with a GnRH antagonist added mid-cycle to prevent premature LH surge.
Antagonist protocols are shorter (roughly 10–14 days versus 3–4 weeks), require fewer injections, and carry a significantly lower risk of OHSS (ovarian hyperstimulation syndrome). If your clinic proposes the long protocol, it's a reasonable question to ask why that protocol was chosen for your specific situation.
The attrition curve is the part most people find hardest to hear once a cycle is underway. Starting from eggs retrieved: typically 70–80% will be mature enough to fertilise; of those, 60–75% will fertilise normally; of fertilised eggs, roughly half to two-thirds will reach day 3; of day-3 embryos, half to two-thirds will make it to blastocyst by day 5.
From ten eggs retrieved, a typical outcome is two to three blastocysts. This is not a failure, it's the biological reality of human embryo development. Most embryos that don't make it to blastocyst were chromosomally abnormal. Knowing this in advance means that getting three blastocysts from ten eggs is good, not disappointing.
Pregnancy rates and live-birth rates are not the same number, and clinics have strong incentives to show you the more favourable one. A clinical pregnancy is a gestational sac visible on ultrasound, this includes pregnancies that will go on to miscarry. A live birth is a baby. At 35, the gap between these two numbers is meaningful.
At 38–40, it's significant. When you're comparing success rates, ask specifically for live-birth rate per cycle started, for your age band. Per egg collection and per transfer are both higher, they exclude failed cycles earlier in the process.
The add-ons question comes up in every IVF cycle and is worth thinking through in advance. ICSI (injecting a single sperm directly into the egg) is specifically indicated for severe male factor, previous fertilisation failure, or frozen sperm, it is not routinely better than standard IVF for other cases, despite being widely offered.
PGT-A (pre-implantation genetic testing) identifies chromosomally normal embryos before transfer; the evidence supports it for recurrent miscarriage, repeated implantation failure, and advanced maternal age, not as a universal improvement. Time-lapse incubators carry an HFEA evidence rating of C. These are worth asking about specifically rather than accepting as default.
Questions to ask before and during the cycle
Before starting: 'What protocol are you using and why, given my AMH and AFC?' This surfaces whether the decision was individualised or default. 'What's your OHSS rate?' At the egg collection results call: 'How many eggs were retrieved, and how many were mature?', the mature figure is what matters. At the day-5 results call: 'How many blastocysts, and what grading system are you using?'
At transfer: 'Are we doing fresh or frozen transfer, and why?' Frozen transfer is now preferred in most cases because it removes the hormonally disrupted environment of a stimulated cycle, if fresh is being proposed, ask the reason. These questions are not difficult or confrontational; they're the questions any well-informed patient should be asking, and good clinics expect them.