Assisted Hatching for Embryos

To help embryos implant in a woman’s uterus and increase the chances of pregnancy success, fertility specialists can use a process called assisted hatching (AH) in conjunction with in vitro fertilization (IVF).

When all goes well during conception, hatching is a natural process that takes place after a sperm fertilizes an egg and creates an embryo. The egg has an outer coating, called the zona pellucida, which holds together the individual cells.

Several days after conception, after the embryo moves from the fallopian tubes to the uterus, the outer zona coating thins, allowing the embryo to break out of the coating and grow larger. This process of hatching is analogous to a chicken hatching out of its egg.

Hatching is required for the embryo to implant in the lining of the uterus. One of the barriers to becoming pregnant is failure of the embryo to hatch and thus failure to implant.

In order to enhance the odds of a successful pregnancy, a fertility specialist may perform assisted hatching in conjunction with IVF.

First, starting on the day of egg retrieval during the IVF process, the female patient receives a combination of steroid medications and antibiotics for six days. Steroids suppress the patient's immune system so that her uterus will not reject the treated embryos. Antibiotics fend off infection within the uterus.

Next, on the third day after egg retrieval, a lab specialist uses either an acid or a laser to dissolve enough of the zona pellucida so that hatching can occur after transfer to the uterus.

One risk is that AH can increase the possibility of identical twins, known as monozygotic twins. In rare instances, the use of steroids can also result in nausea, insomnia, osteoporosis, elevated blood pressure, salt or water retention, higher susceptibility to infection, mood swings, and allergic reactions. The antibiotic used (usually doxycycline) may increase both skin sensitivity to sun light and the risk of vaginal yeast infection.

However, these latter effects are unusual, and the advantage of assisted hatching is that it can significantly boost the odds of a successful pregnancy, especially when handled by an experienced embryologist. This is particularly true for women older than 35, who generally have lower pregnancy rates.