In vitro fertilization works by combining eggs and sperm in a laboratory, then transferring the resulting embryo into the uterus. A full cycle takes about four to six weeks from start to finish, not counting the two-week wait for a pregnancy test afterward. Each phase builds on the last: hormone stimulation, egg retrieval, fertilization, embryo development, and transfer.
Ovarian Stimulation: The First 8 to 12 Days
A natural menstrual cycle produces one mature egg. IVF needs more than that to work with, so the process begins with injectable hormones that push the ovaries to develop multiple eggs at once. These injections contain follicle-stimulating hormone (FSH), the same hormone your body naturally produces, just at higher doses. You’ll typically inject these medications daily for about 8 to 10 days, though some cycles run up to 12 days.
Alongside the stimulation drugs, you’ll also take a medication that prevents your body from releasing the eggs too early. Without this, the natural hormone surge that triggers ovulation could cause you to ovulate before the eggs can be collected. During this phase, you’ll visit the clinic every few days for blood tests and ultrasounds so the medical team can track how many follicles (the fluid-filled sacs that contain eggs) are growing and how large they’ve gotten.
When the follicles reach mature size, a final injection of hCG (human chorionic gonadotropin) triggers the last stage of egg maturation. This shot is timed precisely, usually 36 hours before egg retrieval, because the eggs need to be collected before ovulation occurs on its own.
Egg Retrieval
Egg retrieval is a minor surgical procedure done under sedation, so you’re asleep and comfortable throughout. A doctor inserts an ultrasound probe to locate the mature follicles, then guides a thin needle through the vaginal wall into each follicle. A gentle suction device connected to the needle draws out the fluid and the egg inside it. The whole process usually takes 15 to 30 minutes.
Most people feel crampy or bloated afterward and take the rest of the day off. The eggs go straight to the embryology lab, where they’re evaluated and prepared for fertilization within hours.
Fertilization in the Lab
There are two ways to fertilize the eggs, and the choice depends on the sperm quality and the clinic’s recommendation. In conventional insemination, eggs and sperm are placed together in a dish and the sperm penetrate the eggs on their own, similar to what happens naturally inside the body. In ICSI (intracytoplasmic sperm injection), an embryologist selects a single sperm, draws it into a microscopic glass needle, and injects it directly into the center of the egg.
ICSI is typically used when sperm count or motility is low, or when previous IVF cycles haven’t produced good fertilization rates with the conventional method. Both approaches have similar success rates when used for the right patients. By the next morning, the lab can confirm how many eggs have fertilized successfully.
Embryo Development: Days 1 Through 5
Fertilized eggs don’t become embryos instantly. Over the next several days, cells divide inside a protective shell while the embryology team monitors progress. By day 3, a healthy embryo should contain 6 to 10 cells, with 8 being ideal. At this stage the cells are dividing but the embryo hasn’t actually grown larger than the original egg.
The real transformation happens between days 4 and 5. Cells begin to specialize into two distinct groups: an inner cell mass that will eventually become the fetus, and an outer layer called the trophectoderm that will form the placenta. By day 5, the embryo has reached the blastocyst stage, a hollow ball of roughly 100 or more cells with a fluid-filled cavity inside. This is the stage most clinics prefer for transfer, because blastocysts have higher implantation rates than day-3 embryos.
Not every fertilized egg makes it to blastocyst. It’s common to start with, say, 10 fertilized eggs and end up with 3 or 4 viable blastocysts. The lab grades each embryo based on how well organized its cells look, how much the cavity has expanded, and how tightly packed the cell layers are. Higher-graded embryos generally have better chances of implanting, though lower-graded embryos can and do produce healthy pregnancies.
Optional: Genetic Testing
Before transfer, some patients choose preimplantation genetic testing. An embryologist removes a few cells from the outer layer of the blastocyst (the part that becomes the placenta, not the fetus) and sends them to a genetics lab. This biopsy doesn’t damage the embryo’s development.
There are three types of testing, each looking for something different. PGT-A checks whether the embryo has the correct number of chromosomes, 46 total, since having too many or too few is the leading cause of miscarriage and conditions like Down syndrome or Turner syndrome. PGT-M screens for a specific inherited disease that one or both parents carry, such as cystic fibrosis, sickle cell anemia, or muscular dystrophy. PGT-SR looks for structural problems in the chromosomes themselves, where sections may be flipped or swapped in ways that lead to pregnancy loss.
Genetic testing results typically take a few weeks, which means the embryos are frozen while you wait. This adds time to the overall process but can help the team select the embryo most likely to result in a healthy pregnancy.
Embryo Transfer
Transfer is simpler and faster than most people expect. There’s no anesthesia needed. You’ll be asked to come in with a full bladder, which straightens the uterus and gives the ultrasound a clear view. The doctor threads a thin, flexible catheter through the cervix and into the uterus while watching its path on an abdominal ultrasound screen. The embryo, loaded into the tip of the catheter in a tiny drop of fluid, is deposited about 2 centimeters below the top of the uterine cavity, the spot with the best implantation potential.
After the catheter is withdrawn, the embryologist checks it under a microscope to confirm the embryo was released and wasn’t retained inside. The entire procedure takes about 5 to 10 minutes. Soft catheters and gentle technique are standard because even minor irritation to the uterine lining can trigger contractions that reduce the chances of implantation.
The Two-Week Wait
After transfer, there’s nothing to do but wait. The embryo needs to hatch from its outer shell, attach to the uterine lining, and begin implanting, a process that unfolds over the next several days. Most clinics schedule a blood test 14 days after transfer to measure hCG levels, which confirm whether a pregnancy has begun. Home pregnancy tests can sometimes pick up a result a day or two earlier, but the blood test is more reliable and gives your team a precise hormone level to work with.
During this period, you’ll typically continue taking progesterone (as a suppository, injection, or gel) to support the uterine lining. Many people describe the two-week wait as the hardest part of the entire process, more emotionally taxing than any of the physical procedures.
Risks to Be Aware Of
The most significant medical risk specific to IVF is ovarian hyperstimulation syndrome, or OHSS, where the ovaries overreact to the stimulation medications. Mild symptoms like bloating, nausea, and abdominal discomfort are relatively common. Moderate to severe OHSS, which can involve significant fluid buildup in the abdomen and chest, rapid weight gain, and reduced kidney function, occurs in roughly 1% to 5% of IVF cycles. Modern protocols have reduced these rates further by adjusting medication types and doses for patients at higher risk.
Other risks include minor bleeding or infection from the egg retrieval procedure, and a slightly higher chance of multiple pregnancy if more than one embryo is transferred. Most clinics now transfer a single embryo at a time for this reason.
What It Costs
A single IVF cycle in the United States costs around $21,600 on average when you factor in procedures, monitoring, lab work, and medications. The medications alone run between $2,000 and $7,000 per cycle and typically make up 30% or more of the total bill. Genetic testing, embryo freezing, and frozen embryo transfers add to the cost if needed. Some states mandate insurance coverage for fertility treatment, and many clinics offer payment plans or financing, but out-of-pocket expenses remain substantial for most patients.