In vitro fertilization (IVF) is a fertility treatment where eggs are retrieved from the ovaries, combined with sperm in a laboratory, and the resulting embryo is transferred back into the uterus. The process typically spans two to six weeks of active treatment and produces live births in about 53.5% of cycles for women under 35, with rates declining as age increases. While the concept is straightforward, the actual process involves several carefully timed phases, each designed to maximize the chance of a healthy pregnancy.
Ovarian Stimulation: The First Phase
A natural menstrual cycle usually releases one egg. IVF aims to produce many mature eggs at once, because not every egg will fertilize successfully or develop into a viable embryo. To do this, you take daily hormone injections for 8 to 12 days that stimulate your ovaries to grow multiple follicles, the fluid-filled structures that contain eggs.
These injections are synthetic versions of the hormones your pituitary gland naturally produces to control egg development. Alongside these, you take a second type of medication that prevents your body from ovulating too early, keeping the eggs in place until retrieval. Some protocols also include a “priming” phase before stimulation begins, using estrogen or oral contraceptives for one to three weeks to help synchronize follicle growth.
During stimulation, you’ll visit your fertility clinic four to six times for ultrasounds and blood draws. Each visit takes about 15 to 20 minutes. Your care team tracks how your follicles are growing and adjusts medication doses accordingly. When the largest follicles reach 18 to 22 millimeters, stimulation is complete.
The Trigger Shot and Egg Retrieval
Once your follicles are the right size, you give yourself a precisely timed “trigger shot” that signals your eggs to complete their final stage of maturation. Most women ovulate 37 to 38 hours after this injection, so your retrieval is scheduled about 35 to 36 hours after the trigger, just before ovulation would naturally occur.
Egg retrieval is a short procedure, typically lasting 20 to 30 minutes. You receive intravenous sedation, and a thin needle is guided through the vaginal wall into each ovary using ultrasound. The fluid inside each follicle, which contains the eggs, is drawn out and immediately passed to embryologists in the lab. You rest in recovery for about an hour afterward and need someone to drive you home.
Most women feel pelvic heaviness, cramping, and light spotting for the next day or two. Many return to work the day after retrieval, though some take an extra day. Your ovaries remain enlarged for several weeks, so you’ll need to avoid heavy exercise, swimming, and baths during that time.
Fertilization in the Lab
Two to four hours after retrieval, embryologists combine the eggs with sperm using one of two methods. In conventional insemination, healthy sperm are placed alongside each egg in an incubator and fertilization happens on its own. In the second method, called ICSI, a single sperm is injected directly into each egg. ICSI was originally developed for cases of low sperm count or poor sperm motility, but it’s also used when fewer eggs are available or when conventional insemination has failed in a previous cycle.
By the next morning, about 18 to 24 hours after the eggs and sperm come together, embryologists can confirm which eggs have fertilized. Each fertilized egg, now called a zygote, begins dividing. Over the next five to six days, viable embryos develop into blastocysts, rapidly dividing balls of roughly 100 cells.
Genetic Testing of Embryos
Before transfer, many clinics offer the option to screen embryos for chromosomal abnormalities. A small sample of 5 to 10 cells is taken from the outer layer of the blastocyst and analyzed. The test checks whether the embryo has the correct 46 chromosomes or has extra or missing copies, a condition called aneuploidy. Aneuploidy is the leading cause of implantation failure and early miscarriage, and it becomes more common with age.
Modern testing can also detect mosaicism, where some cells in the embryo are chromosomally normal and others are not, as well as smaller structural changes like missing or duplicated chromosome segments. Results typically categorize embryos along a spectrum rather than a simple normal-or-abnormal label, which gives your fertility team more information when selecting which embryo to transfer.
Fresh vs. Frozen Embryo Transfer
After fertilization, embryos can be transferred into the uterus right away (fresh transfer) or frozen for a later cycle. Freezing has become increasingly common, and research supports the shift. One study found a clinical pregnancy rate of 47.5% with frozen transfers compared to 35.5% with fresh transfers. Live birth rates were also significantly higher in the frozen group (38.8% vs. 15.7%), and rates of preterm delivery, low birth weight, and multiple pregnancies were all lower.
The likely reason is timing. Ovarian stimulation floods your body with hormones that can disrupt the uterine lining, making it less receptive to an embryo. Freezing the embryo and transferring it in a later cycle allows your uterine lining to develop under more natural hormonal conditions, improving synchrony between the embryo and the endometrium. Freezing also eliminates the risk of ovarian hyperstimulation syndrome in that cycle, since no transfer-supporting hormones are needed right away.
The Embryo Transfer Itself
Embryo transfer is simpler than retrieval. It doesn’t require sedation and takes only a few minutes. A thin catheter is threaded through the cervix, and the embryo is deposited into the uterus using ultrasound guidance. Most clinics transfer a single embryo to reduce the risk of twins or higher-order multiples. After the transfer, you typically wait about 10 to 14 days before taking a pregnancy test.
Success Rates by Age
Age is the single strongest predictor of IVF success. National data from 2022 show live birth rates per intended egg retrieval of 53.5% for women under 35, 39.8% for women 35 to 37, and 25.6% for women 38 to 40. These numbers reflect all embryo transfers from a single retrieval, including frozen transfers done weeks or months later.
The decline with age is driven by egg quality. As women get older, a higher proportion of their eggs carry chromosomal abnormalities, which means fewer embryos are viable after fertilization and testing. This is also why some women undergo multiple retrieval cycles to bank enough healthy embryos before attempting a transfer.
Risks and Side Effects
The most significant medical risk of IVF is ovarian hyperstimulation syndrome (OHSS), where the ovaries overreact to stimulation medications and swell painfully. Moderate to severe cases occur in roughly 1% to 5% of IVF cycles. Symptoms include bloating, nausea, and in serious cases, fluid accumulation in the abdomen. Clinics reduce this risk by tailoring medication doses to your ovarian reserve, using specific medication protocols for high-risk patients, and opting for a freeze-all approach instead of a fresh transfer when warning signs appear.
Other common side effects are milder: bloating, breast tenderness, mood swings, and injection-site bruising during stimulation. The retrieval itself carries a small risk of bleeding or infection. Emotionally, the process can be taxing. The combination of hormonal fluctuations, frequent clinic visits, financial pressure, and uncertain outcomes makes each cycle mentally demanding, even when everything goes smoothly.
What IVF Costs
A single IVF cycle in the United States typically costs $12,000 to $18,000, covering consultations, monitoring, egg retrieval, lab fertilization, and embryo transfer. Medications are usually billed separately and add another $3,000 to $5,000. Genetic testing, embryo freezing, and frozen transfer cycles carry additional fees. Many people need more than one cycle, so total costs can climb quickly. Insurance coverage varies widely by state and employer, so it’s worth checking your specific plan before starting treatment.