A single IVF cycle moves through five main stages: ovarian stimulation, egg retrieval, fertilization, embryo development, and embryo transfer. From the first hormone injection to a pregnancy test, the process typically spans four to six weeks. Here’s what happens at each stage and what the experience actually feels like.
Stage 1: Ovarian Stimulation
The goal of this first stage is to coax your ovaries into producing multiple mature eggs instead of the single egg released in a normal menstrual cycle. You’ll inject a follicle-stimulating hormone (common brand names include Gonal-F, Follistim, and Menopur) daily for about 8 to 10 days, though the range can stretch from 7 to 12 days depending on how your body responds.
Alongside the stimulating hormone, you’ll also take a second medication to prevent your body from releasing the eggs too early. This is either started before stimulation begins or added partway through, depending on the protocol your clinic uses. During this phase, you’ll visit the clinic several times for blood draws and ultrasounds so your doctor can track how many follicles are growing and how large they’ve become.
Once enough follicles reach mature size, you’ll take a “trigger shot” of hCG, which tells the eggs to complete their final stage of development. The timing of this shot is precise: egg retrieval is scheduled about 36 hours later. Many people find stimulation the most physically demanding part of IVF. Bloating, mild pelvic pressure, and mood swings from the hormones are common.
Stage 2: Egg Retrieval
Egg retrieval is a short surgical procedure, typically lasting 10 to 20 minutes. You’ll receive intravenous sedation, so you’re asleep and won’t feel anything during the process. Your doctor uses an ultrasound-guided needle passed through the vaginal wall to reach each ovarian follicle and suction out the fluid containing the egg.
The number of eggs collected varies widely based on your age, ovarian reserve, and how well you responded to stimulation. Your doctor will have a rough estimate from ultrasound monitoring, but the exact count isn’t confirmed until the embryology team examines the fluid under a microscope. Most people feel crampy and bloated afterward and take the rest of the day off. Recovery is usually quick, with most discomfort resolving within a day or two.
One risk worth knowing about is ovarian hyperstimulation syndrome (OHSS), where the ovaries over-respond to the hormones and swell painfully. Moderate to severe cases have historically occurred in about 1% to 5% of IVF cycles, though modern protocols have made serious cases less common.
Stage 3: Fertilization
On the same day as egg retrieval, a sperm sample is collected (from a partner or donor) and prepared in the lab. Fertilization happens one of two ways. In conventional IVF, sperm are placed in a dish with each egg and left to fertilize naturally. In ICSI (intracytoplasmic sperm injection), a single sperm is injected directly into each mature egg. ICSI is typically used when sperm count or motility is low, or when previous cycles had poor fertilization rates.
The embryology team checks the eggs the following morning. Not every egg will fertilize successfully. A fertilization rate of about 70% to 80% of mature eggs is considered normal, but this varies.
Stage 4: Embryo Development
Fertilized eggs are placed in an incubator that mimics the conditions inside the body. Over the next several days, embryologists monitor how the embryos divide and grow. This stage requires no clinic visits from you; the lab does the work.
By day 3, a healthy embryo should have between 6 and 10 cells, with 8 being ideal. Embryologists grade these early-stage embryos based on how evenly the cells divide and how much fragmentation (small cellular debris) is present. Up to 20% fragmentation is considered acceptable.
Most clinics now culture embryos to day 5 or 6, when they reach the blastocyst stage. At this point, the embryo has differentiated into two distinct parts: an inner cell mass (which becomes the baby) and an outer layer of cells (which becomes the placenta). Blastocysts are graded with a number and two letters. The number (1 through 6) describes how expanded the embryo is. The first letter grades the inner cell mass, and the second grades the outer layer. An “A” in either position means tightly packed, well-organized cells.
Not all embryos make it to the blastocyst stage. It’s common for the number to drop significantly between day 1 and day 5. While this can feel discouraging, culturing to day 5 helps identify the embryos with the strongest developmental potential.
Genetic Testing
If you opt for preimplantation genetic testing (PGT-A), a few cells are biopsied from the outer layer of each blastocyst on day 5 or 6 and sent to a genetics lab. The embryos are frozen while results come back, which typically takes one to two weeks. PGT-A screens for chromosomal abnormalities and can reduce the chance of transferring an embryo that wouldn’t implant or would result in miscarriage. However, it also reduces the number of embryos available for transfer, since some will come back abnormal. If you’re doing PGT-A, your transfer will be a frozen embryo transfer in a later cycle rather than a fresh transfer.
Stage 5: Embryo Transfer
Embryo transfer is the simplest procedure in the entire process. It takes just a few minutes, requires no anesthesia, and feels similar to a Pap smear. Your doctor threads a thin, flexible catheter through the cervix and deposits the embryo into the uterus. In many clinics, ultrasound is used to guide catheter placement, which research has linked to improved pregnancy and live-birth rates, particularly in cases where the transfer might otherwise be tricky.
Before the transfer, the cervical mucus is typically cleared away, a small step that has been shown to improve outcomes. Most clinics now transfer a single embryo to reduce the risk of twins or higher-order multiples.
You may have either a fresh transfer (using an embryo from the current cycle) or a frozen transfer (using an embryo that was cryopreserved from a previous retrieval or after genetic testing). Frozen transfers happen on a separate timeline, with your uterine lining prepared using estrogen and progesterone beforehand.
Progesterone Support After Transfer
Starting on the day of or the day after egg retrieval, you’ll begin progesterone supplementation to support the uterine lining. Progesterone can be given as intramuscular injections, vaginal suppositories, gels, or tablets. This continues through the waiting period and, if the cycle results in pregnancy, often throughout the first trimester.
The Two-Week Wait and Pregnancy Test
After the transfer comes the part many people find hardest: waiting. Your clinic will schedule a blood pregnancy test about 16 days after egg retrieval. Testing earlier at home is unreliable because the trigger shot (hCG) can linger in your bloodstream for 8 to 10 days and produce a false positive.
Success Rates by Age
IVF success depends heavily on the age of the person providing the eggs. The most recent national data from the Society for Assisted Reproductive Technology (SART), covering 2023 cycles using the patient’s own eggs, shows live birth rates per intended egg retrieval of:
- Under 35: 53.2%
- 35 to 37: 39.9%
- 38 to 40: 26.2%
- 41 to 42: 13.2%
- Over 42: 4.1%
These numbers represent live births from all transfers resulting from a single egg retrieval, including any frozen embryo transfers that followed. That means if you bank embryos from one retrieval and transfer them across multiple cycles, the cumulative odds can be higher than a single-cycle snapshot suggests. Using donor eggs from a younger person also changes the equation significantly, as success rates track with egg age rather than the age of the person carrying the pregnancy.