# Stimulation and Laboratory Risks

Stimulation and Laboratory Risks (Egg Freezing)

Throughout treatment, the care team monitors the patient's near-term safety while taking stimulation drugs. Patients may also wonder about long-term health risks of fertility medications. Both warrant brief explanations.

Stimulation medications are designed to encourage multiple follicles to grow. Occasionally, the ovaries respond more strongly than expected. This is called ovarian hyperstimulation syndrome, or OHSS. Some people are predisposed to a stronger response than others. That's one reason stimulation protocols are individualized, and why the care team monitors ultrasounds and bloodwork closely throughout.

When OHSS occurs, it's most often mild — some bloating and discomfort that resolves on its own within one to two weeks. This happens in roughly 5 to 10 percent of stimulation cycles. Egg freezing and ‘freeze all’ IVF cycles don't involve a fresh embryo transfer — which can trigger late-onset OHSS when the embryo implants and produces hCG naturally. Therefore, OHSS is even less common with these cycle types, occurring in fewer than 0.5 percent.

If OHSS does occur, it is managed effectively with hydration and, when needed, drainage of accumulated fluid. Advances in fertility medicine, such as a Lupron trigger, have significantly reduced how often OHSS occurs and how severe it tends to be.

The second topic worth addressing is a question that emerged in the 1990s. Back then, a small number of studies suggested fertility medications might be linked to increased cancer risk. More recent research — conducted across much larger populations — did not confirm those findings. It also identified a key flaw in the original studies: infertility itself carries a modestly elevated cancer risk, independent of any treatment. The earlier studies hadn't accounted for that.

Since then, millions of people have gone through fertility treatment. The current body of evidence does not show an increased cancer risk from fertility medications or treatments. Patients with a personal or family history of hormone-sensitive cancer should discuss this history with their care team, to determine whether the history warrants any modification to their treatment protocol.

The embryology lab operates under strict protocols designed to protect eggs at every step. The most fundamental of these is patient identification — ensuring that the right eggs, sperm, and/or embryos are always matched to the right person and procedure. These checks happen continuously throughout the cycle, not just once.

The lab also maintains backup systems — including emergency power generation — to protect against equipment failure and minimize disruption to stored eggs and active cycles.

Even with these safeguards in place, it's important to understand that laboratory work of this complexity carries some inherent risk. Equipment can malfunction. Human error, however rare, can occur even among highly trained embryologists. In very uncommon cases, a lab accident — such as a broken instrument or compromised handling — can risk damage to or loss of eggs. In extreme circumstances, a natural disaster could affect the facility.

These events are rare. The protocols, redundancies, and oversight systems in place are specifically designed to keep them that way. In the unlikely event that anything affects stored eggs, your care team will contact you directly.

If you have any questions about your individual risk, reach out to your care team who can work through them with you.
