IVF works by stimulating your ovaries to produce multiple eggs, retrieving those eggs, fertilizing them in a lab, and then transferring a resulting embryo back into your uterus. The full process takes roughly two to six weeks per cycle, depending on whether you do a fresh or frozen embryo transfer. Here’s what each stage actually looks like.
Ovarian Stimulation: The First 8 to 14 Days
In a natural cycle, your body releases one egg per month. IVF overrides that system. For about 8 to 14 days, you inject synthetic hormones that mimic the signals your brain normally sends to your ovaries, pushing multiple follicles (the fluid-filled sacs that contain eggs) to grow at the same time. The goal is to retrieve as many mature eggs as possible in a single cycle.
During this phase, you’ll visit your clinic every few days for ultrasounds and blood draws. Your doctor is tracking follicle size in millimeters. Once two or three follicles reach about 17 to 18 mm in diameter, you’re ready for the next step. Follicles in the 12 to 19 mm range on the day of the trigger are the ones most likely to contain a mature egg.
At that point, you take a “trigger shot,” a hormone injection that signals your eggs to complete their final maturation. Timing here is precise: your egg retrieval will be scheduled about 36 hours later.
Egg Retrieval
The retrieval itself is quick, typically 15 to 20 minutes. You’re under anesthesia the entire time. Your doctor passes a thin needle through the vaginal wall and into each ovary using ultrasound for guidance. The needle draws out the fluid from each follicle, and an embryologist examines that fluid under a microscope to identify the eggs.
Recovery takes about an hour. You’ll rest with water and a light snack, and a nurse will check your pain levels before you leave. Most women feel some cramping and bloating afterward, similar to a heavy period. You’ll need someone to drive you home because of the anesthesia.
Fertilization in the Lab
Once the eggs are collected, there are two ways they can be fertilized. In conventional IVF, sperm are placed in a dish alongside each egg and left to fertilize on their own. In the second method, called ICSI, an embryologist selects a single sperm and injects it directly into the egg.
ICSI was originally developed for male factor infertility (low sperm count or poor motility), but clinics now use it in a wider range of situations: when previous IVF cycles had unexpectedly low fertilization, when eggs have been previously frozen, when genetic testing of embryos is planned, or when egg quality is a concern. For frozen eggs specifically, ICSI is the preferred fertilization method because the freezing process hardens the egg’s outer shell, making it harder for sperm to penetrate naturally.
Embryo Development: Day 1 Through Day 5
After fertilization, embryos grow in an incubator that mimics the conditions inside your body. The embryology team monitors them daily. By day 3, a healthy embryo has divided into about eight or more cells. By day 5, the strongest embryos have reached the blastocyst stage, a more complex structure with two distinct cell types: an inner cell mass (which becomes the fetus) and an outer layer called the trophectoderm (which becomes the placenta).
Not every fertilized egg makes it to day 5. It’s common for a significant portion to stop developing along the way, which is one of the emotionally difficult parts of IVF. Embryologists grade the surviving blastocysts based on the size of the fluid-filled cavity inside, the quality of the inner cell mass, and how evenly the outer cell layer is distributed. These grades help your doctor choose the best embryo for transfer.
Optional Genetic Testing
Before transfer, you may have the option to genetically screen your embryos. The most common test checks whether each embryo has the correct number of chromosomes (23 pairs). An embryo with extra or missing chromosomes is less likely to implant and more likely to miscarry.
To perform the test, the embryologist removes a few cells from the outer layer of the blastocyst and sends them to a genetics lab. Results usually take one to two weeks, which means your embryos will be frozen while you wait. The testing is especially relevant for women over 35. Data from the Society for Assisted Reproductive Technology shows that miscarriage rates drop meaningfully with tested embryos in older age groups: for women 38 to 40, the miscarriage rate was about 14% with testing compared to 28% without. For women 41 to 42, it was 14% versus 38%. The benefit narrows for younger women, where miscarriage rates are already lower.
Fresh vs. Frozen Embryo Transfer
Your embryo can be transferred during the same cycle as your egg retrieval (a fresh transfer) or frozen and transferred in a later cycle. The trend toward freezing all embryos, sometimes called a “freeze-all” strategy, became popular because the hormone stimulation drugs can temporarily alter the uterine lining, potentially making it less receptive to an embryo. Freezing lets your body return to a more natural hormonal state before the transfer.
That said, the choice isn’t one-size-fits-all. A 2024 randomized trial published in The BMJ found that for women with a low prognosis (fewer eggs or embryos to work with), fresh transfers actually produced higher live birth rates than frozen: 40% versus 32%. Your clinic will weigh your specific situation, including whether you’re doing genetic testing, how your lining looks, and whether you’re at risk for ovarian hyperstimulation.
The Embryo Transfer
The transfer itself is one of the simplest parts of the process. It takes just a few minutes and usually doesn’t require anesthesia. Your doctor threads a thin, flexible catheter through your cervix and places the embryo into your uterus, guided by ultrasound. You’ll likely be asked to come with a full bladder, which helps the ultrasound image. Most women describe the sensation as similar to a Pap smear.
Progesterone Support After Transfer
After transfer, you’ll start progesterone supplementation if you haven’t already. Progesterone is the hormone that thickens and stabilizes the uterine lining, creating the right environment for an embryo to implant. During IVF, your body may not produce enough on its own because the egg retrieval disrupts the ovary’s normal hormone production.
The most common delivery method is vaginal suppositories or inserts, which avoid the pain and soreness of intramuscular injections while producing similar pregnancy outcomes. You’ll typically continue progesterone through the first 8 to 10 weeks of pregnancy, at which point the placenta takes over hormone production. This is one of the less-discussed but persistent parts of IVF: weeks of daily medication that can cause bloating, fatigue, and mood changes.
The Two-Week Wait and Pregnancy Test
After the transfer comes the hardest part for many women: waiting. Your clinic will schedule a blood test to measure levels of the pregnancy hormone hCG, usually about 9 to 14 days after transfer. Under normal conditions, hCG becomes detectable about 10 days after conception and doubles roughly every two to three days in the first four weeks of pregnancy.
Some research suggests that hCG can be detected as early as 5 days after a frozen embryo transfer, but most clinics wait longer to avoid ambiguous results. A positive blood test will be followed by a second test two to three days later to confirm that levels are rising appropriately. If they are, you’ll be scheduled for an early ultrasound around six to seven weeks of pregnancy to check for a heartbeat.
It’s worth knowing that a single IVF cycle doesn’t always result in pregnancy. Success rates vary widely based on age, egg quality, and the number of embryos available. Many women go through two or three cycles before achieving a pregnancy, and some freeze embryos from one retrieval to use across multiple transfer attempts. Each transfer is physically much easier than the initial stimulation and retrieval, since the most intensive part of the process has already been completed.