Assisted hatching is a laboratory technique used during IVF where an embryologist creates a small opening in the outer shell of an embryo before it’s transferred to the uterus. The goal is to help the embryo break free from that shell and attach to the uterine lining, a step that’s essential for pregnancy to begin. It’s one of several optional add-on procedures offered at fertility clinics, typically costing around $500 on top of a standard IVF cycle.
Why the Embryo’s Shell Matters
Every embryo is surrounded by a protein shell called the zona pellucida. In a natural pregnancy, the embryo sheds this shell on its own a few days after fertilization, a process called “hatching.” Once free, the embryo can implant into the uterine wall. During IVF, some embryos may have difficulty completing this step. The shell can be unusually thick (greater than 15 micrometers), hardened by the freezing and thawing process, or simply slower to break down in embryos that aren’t developing at a typical pace.
Assisted hatching bypasses this potential barrier by creating a gap in the shell before the embryo is placed in the uterus. The idea is straightforward: if the shell is part of the problem, removing that obstacle should give the embryo a better chance of implanting.
How the Procedure Works
Assisted hatching is performed in the lab, not in your body. An embryologist works on the embryo under a microscope shortly before the embryo transfer, which can happen on day 3, 5, or 6 after fertilization. The procedure takes only a few minutes and uses one of three main approaches.
Laser is the most widely used method. A precisely focused infrared laser either drills a small hole through the shell or thins a section of it. It’s fast, consistent, and easy to control. Chemical methods use a mild acid solution to dissolve a small area of the shell. This approach works but carries a higher risk of damaging the shell unevenly or affecting the embryo itself, especially when a lab is processing many embryos at once. Mechanical methods involve using a fine glass needle to physically nick or cut open part of the shell. This requires significant skill and is more time-consuming, making it less common in modern labs.
Laser-assisted hatching has largely replaced the other two techniques because of its precision and reproducibility. Within the laser category, clinics use either a drilling approach (punching a hole) or a thinning approach (shaving down a section of the shell without fully breaking through). Both strategies aim to weaken the shell enough that the embryo can escape on its own once it starts expanding.
Who It’s Recommended For
Assisted hatching is not typically offered to every IVF patient. The strongest evidence of benefit applies to people with a poor prognosis, specifically those who have gone through two or more failed IVF cycles and older women, generally 38 and above. In these groups, pregnancy and implantation rates do appear to improve with assisted hatching.
Beyond repeated IVF failure and age, clinics may recommend assisted hatching for embryos with a thick shell, slow development, heavy fragmentation, or otherwise poor morphology. Elevated baseline FSH levels in the woman providing eggs can also factor into the decision, since this hormone marker is associated with diminished ovarian reserve and lower embryo quality.
For patients who don’t fit these categories, the case for assisted hatching is weaker. The American Society for Reproductive Medicine’s guideline on the procedure states clearly that routine use for all IVF patients is not supported by the evidence.
What the Success Rates Actually Show
The data on assisted hatching is more nuanced than a simple “it works” or “it doesn’t.” A large propensity-weighted analysis found that after adjusting for patient differences, the clinical pregnancy rate was 29.6% with assisted hatching compared to 31.3% without it, and the live birth rate was 21.2% versus 22.4%. Those differences are small but statistically significant, and they point in the wrong direction for routine use.
The picture changes depending on who’s receiving the treatment and what type of embryo transfer is being done. For women under 35 using frozen-thawed blastocysts, the live birth rate was slightly higher with assisted hatching (37.6% versus 36.9%). But for fresh cleavage-stage transfers across all ages, frozen cleavage-stage transfers in women over 35, and frozen blastocyst transfers in women over 40, outcomes were actually worse with assisted hatching than without it.
This is why the procedure remains targeted rather than universal. The benefit seems to exist for specific subgroups, particularly patients with repeated implantation failure, but applying it broadly can dilute or even reverse any advantage.
Risks to Know About
Assisted hatching is a low-risk procedure, but it isn’t zero-risk. The most immediate concern is embryo damage during the process itself. Though rare with modern laser techniques, there’s always a small chance that the manipulation harms the embryo’s cells rather than just the shell.
A more widely discussed concern is the potential link to identical twinning. IVF in general produces identical (monozygotic) twins at a higher rate than natural conception, roughly 1% to 2.4% compared to 0.4% in the general population. Assisted hatching has historically been listed as one possible contributor, with the theory being that a partial opening in the shell could cause the embryo to split as it squeezes through. However, the largest study to date on this question, analyzing over 154,000 live births from single embryo transfers, found that assisted hatching did not have a significant independent effect on identical twinning rates after accounting for other variables. Blastocyst transfer turned out to be the stronger risk factor.
There are no known long-term health risks to children born after assisted hatching, but the technique has been in use for a relatively short period compared to IVF itself.
Cost and What to Expect
At most U.S. fertility clinics, assisted hatching is offered as an add-on service at a national average of about $500 per cycle. Some clinics include it as a standard part of their IVF protocol at no extra charge. Given that a full IVF cycle in the United States typically runs between $19,000 and $29,700, the add-on cost is relatively small, but it adds up over multiple cycles.
From your perspective as a patient, assisted hatching doesn’t change anything about the embryo transfer experience. You won’t feel anything different, and the transfer process itself is identical. The work happens entirely in the lab beforehand. If your clinic recommends it, the only decision you need to make is whether the potential benefit justifies the added cost for your specific situation. Asking your clinic why they’re recommending it for you, and whether you fit the profile of patients most likely to benefit, is a reasonable conversation to have before agreeing.