Egg retrieval typically happens on days 13 to 14 of an IVF cycle, roughly 36 hours after a precisely timed “trigger shot” that signals your eggs to complete their final stage of maturation. The exact day varies from person to person because your clinic monitors how your follicles are developing and only schedules the retrieval once they reach the right size.
Where Retrieval Falls in the IVF Timeline
An IVF cycle begins with ovarian stimulation, a phase where you inject hormones daily to encourage multiple follicles to grow at once rather than the single follicle your body would normally produce. This stimulation phase lasts roughly 8 to 12 days. During that time, you’ll visit your clinic every few days for ultrasounds and blood work so your team can track how many follicles are growing and how large they are.
Once your follicles reach the target size, your clinic will schedule the trigger shot. This injection is given around days 9 to 12 of the cycle, usually late at night. The retrieval then follows approximately 36 hours later, landing on days 13 to 14. That window isn’t arbitrary. Studies on ovulation physiology show that follicles begin to rupture on their own around 38 to 39 hours after the trigger, so clinics aim to collect the eggs before that happens.
How Your Clinic Decides You’re Ready
The trigger shot isn’t scheduled by the calendar. It’s scheduled by your follicles. At each monitoring appointment, your clinic measures your follicles via ultrasound. The standard threshold is two to three follicles reaching at least 17 to 18 millimeters in diameter. Research published in Frontiers in Endocrinology found that follicles between 12 and 19 millimeters on the day of the trigger contributed the most mature eggs at retrieval, so clinics are looking for a cluster of follicles in that range, with the lead follicles hitting that 17 to 18 mm mark.
Your blood estrogen levels also factor in. As follicles grow, they produce estrogen, and rising levels confirm that the eggs inside are developing properly. If your follicles are the right size but your hormone levels lag behind, or vice versa, your clinic may adjust your medication dose or delay the trigger by a day or two.
Why the Trigger Shot Timing Is So Precise
The trigger shot is the most time-sensitive step in the entire IVF process. Your clinic will give you a specific hour to administer it, sometimes down to the minute, because the retrieval is booked exactly 36 hours later. If you take the shot too early, the eggs may ovulate before the procedure. Too late, and they may not be fully mature.
There’s some nuance in the research about the ideal window. A meta-analysis in the Journal of Assisted Reproduction and Genetics found that waiting 38 hours rather than 36 produced more high-quality embryos, likely because the extra time allows better blood flow to the follicles and improved oxygen delivery to the maturing eggs. However, waiting too long carries risk. Spontaneous ovulation becomes a concern around 39 hours, at which point the eggs would be released into the body and become unretrievable. Most clinics stick close to the 36-hour mark to balance egg quality against the risk of losing them.
What Happens During the Procedure
The retrieval itself is a short procedure, typically lasting 15 to 30 minutes. You’ll be sedated for it. In the United States, about 95% of clinics use conscious sedation, where you’re given intravenous medication that keeps you comfortable and drowsy but doesn’t require a breathing tube. In the UK, sedation is also the most common approach, used at roughly 84% of centers. General anesthesia and regional options like spinal blocks are available but less frequently used.
Your doctor uses an ultrasound-guided needle inserted through the vaginal wall to reach each ovary. The needle punctures each mature follicle and suctions out the fluid, which contains the egg. An embryologist in the adjacent lab examines the fluid immediately to confirm each egg has been collected.
How Many Eggs to Expect
The number of eggs retrieved depends heavily on age and ovarian reserve. A study of over 3,400 cycles found clear patterns:
- Under 30: an average of about 18 to 19 eggs
- 30 to 35: around 15 eggs
- 36 to 37: around 13 eggs
- 38 to 39: roughly 10 to 11 eggs
- 40 to 44: about 8 eggs
- 45 and older: around 4 to 5 eggs
More eggs don’t always mean better outcomes. The best live birth rates are associated with retrieving 11 to 15 eggs. For women aged 35 to 39, the strongest pregnancy outcomes were actually seen with a more modest 5 to 9 eggs. Quality matters more than quantity, and overstimulating the ovaries carries its own risks.
Preparing for Retrieval Day
Because sedation is involved, you’ll need to fast for at least 7 hours before the procedure. That means no food or drink, including water, from the night before if your retrieval is scheduled in the morning. You’ll also stop your stimulation injections after the trigger shot, so you won’t need any more injections in the day or two before retrieval. Some clinics ask you to take a pain-relief suppository about an hour before the procedure to help with post-operative discomfort.
You’ll need someone to drive you home afterward, since you won’t be cleared to drive for 24 hours following sedation.
Recovery After the Procedure
You’ll spend a few hours recovering at the clinic before being sent home. Cramping and mild bloating are normal and can last a few days. Some women experience nausea from the sedation, which usually resolves within several hours. Bland foods and plenty of fluids help. Most people return to work the next day without complications.
A small percentage of patients, roughly 1% to 5% of IVF cycles, develop ovarian hyperstimulation syndrome (OHSS) in the days following retrieval. This happens when the ovaries overreact to stimulation hormones, causing fluid to shift out of the bloodstream and into the abdomen. Mild cases involve bloating and discomfort. More severe cases can cause significant abdominal swelling, shortness of breath, and rapid weight gain. If your abdomen swells noticeably, you feel short of breath, or you gain more than a couple of pounds overnight, contact your clinic right away.
What Comes Next
Once eggs are retrieved, they’re fertilized in the lab, either by mixing them with sperm or through direct injection of a single sperm into each egg. Embryos develop over the next 5 to 6 days while your body recovers. If you’re doing a fresh embryo transfer, the transfer typically happens 3 to 5 days after retrieval. If embryos are being frozen for a later transfer, you’ll have a recovery cycle before the next steps.
For fresh transfers, you’ll start progesterone supplementation shortly after retrieval to prepare your uterine lining. The timing of progesterone initiation varies between clinics, but it generally begins within a day or two of retrieval, roughly 36 hours after the trigger shot’s effects, to mimic the natural hormonal shift your body would make after ovulation.