IVF can look like a factory process because it involves multiple steps that happen in a very specific order, and after each step we have less “material” (in this case eggs or embryos) to work with.
To illustrate the point, we’ve outlined how this process might look for a 32-year-old woman who’s had a successful IVF cycle. It’s worth noting that for many women and couples, the number of eggs or embryos after each step may not look this good.
During each step of the IVF process, a doctor and patient can make decisions to help ensure that more eggs or embryos are available, raising the odds the IVF cycle leads to a healthy delivery (and perhaps allowing for the creation and storage of additional embryos that can be used to have more children later).
During the ovarian stimulation phase, most women inject themselves with hormones that directly act on the ovaries to grow a large number of follicles, each of which houses an egg. Generally speaking, the “stimulation and monitoring” period lasts about 10 days for most women.
The major decision at this point is which combination of drugs (called a “protocol”), and at which doses, a woman should take. Generally speaking, more drugs equates to producing more eggs and so a great question to ask is “why wouldn’t you always take the maximum amount possible?”
We love the dataset below of 38,000 IVF patients which shows that, yes, producing more eggs drives more live births, but only up to a point. Once a woman produces about 15 - 20 eggs in a cycle, her odds of having a birth from that cycle stop increasing. But what does increase is the odds she over stimulates and develops ovarian hyperstimulation syndrome, or OHSS. OHSS is excruciatingly painful and in some case can be dangerous.
Additionally, taking higher doses of drugs costs more money. Beyond a certain point, at best that extra expense is “money down the drain” because it doesn’t improve the odds of having a child. At worst, it imperils a woman’s health by raising the odds she hyperstimulates.
During this time the patient returns to the doctor’s office on up to a daily basis to have her blood drawn, and ultrasounds taken, to chart how many follicles are growing and to adjust dosing.
When a doctor is satisfied with the number and size of the follicles, the patient will take a drug to force the eggs to “mature.” Thirty-five to thirty-six hours later, a fertility doctor will use a small needle, using ultrasound guidance, to pierce through the vaginal wall to access the ovaries. At the end of that needle is a small vacuum that drains the follicles and retrieves the eggs. This procedure is typically done with either sedation or a light anesthesia. The procedure is done as an "out-patient." Usually, the recovery is brief with patients returning to routine daily activities over the next few days. Mild cramping and light vaginal spotting may occur.
Many women are surprised to learn that they end up with fewer eggs retrieved than the number of follicles that were growing. That’s because only about 75% of large follicles produce a “mature” egg.
One decision to consider is whether the doctor should try and drain smaller follicles to see if they may hold mature eggs, though they’re unlikely they to. And again, after a certain number of mature eggs (~15 - 20) are retrieved, the data shows that success rates don’t improve.
The data below on egg freezers from NYU treated from 2007 to 2014 illustrates an important point: the number of mature eggs retrieved tends to decrease with age. However, we wouldn’t focus too long on the specific numbers in the Y-axis because these are egg freezers, and they haven’t experienced trouble conceiving, so they may be more fertile than women doing IVF.
Once mature eggs are retrieved, they need to be placed in a petri dish and fertilized with sperm.
The major decision at this point is the technique your clinic’s laboratory uses to fertilize the eggs. Conventional Insemination involves surrounding the eggs with washed sperm. Intracytoplasmic Sperm Injection, or ICSI, involves injecting a single sperm directly into the egg.
You need to ensure your doctor & clinic don’t just put this decision on “auto-pilot.” As you can see below in the nationally-reported data, nearly all patients end up having their eggs fertilized with ICSI, whether it’s needed or not.
This matters because while ICSI is clearly helpful for some types of patients (and often has higher fertilization rates than Conventional Insemination), in many patients the data shows it drives no higher rate of success (and in some types of patients it correlates with lower rates of success).