Assisted hatching (AH) is a laboratory procedure used alongside in vitro fertilization (IVF) treatment. It modifies an embryo’s outer layer to potentially aid its successful implantation into the uterine wall. For pregnancy to occur, an embryo must naturally break free from its protective shell, allowing it to attach to the uterine lining. This article explores assisted hatching, including when fertility specialists might consider it, its purpose, and the factors influencing this decision.
What Assisted Hatching Is
An embryo is encased by a protective outer layer known as the zona pellucida, often described as its “shell.” For pregnancy to establish, the embryo must naturally emerge or “hatch” from this zona pellucida, allowing it to attach to the uterine lining. Assisted hatching is a micro-manipulation technique performed in the laboratory to create a small opening or thin this outer layer, facilitating this crucial step.
The procedure is typically carried out on the third or fifth day of embryo development, before embryo transfer. Laser-assisted hatching is the most commonly employed method due to its precision, speed, and safety. This involves using a focused laser to create a microscopic hole or thin a portion of the zona pellucida. Other techniques include chemical methods, which use an acidic solution, and mechanical methods, involving a fine needle. The goal is to provide the embryo with an easier pathway for hatching, potentially facilitating implantation.
When Assisted Hatching May Be Recommended
Assisted hatching is not universally recommended for all in vitro fertilization cycles; its consideration is based on specific patient profiles and embryo characteristics. One common scenario involves women of advanced maternal age, typically over 37 or 38 years old. As women age, the zona pellucida surrounding their embryos can become thicker or harder, which might hinder the embryo’s ability to naturally hatch and implant.
Embryos possessing a naturally thick or unusually hard zona pellucida are another indication for assisted hatching, regardless of maternal age. This physical characteristic can impede the embryo’s emergence, making it difficult for it to attach to the uterine wall. Embryos that have undergone cryopreservation (frozen and thawed) are also often candidates. The process of freezing and thawing can cause the zona pellucida to harden, potentially making natural hatching more challenging.
Patients who have experienced multiple unsuccessful in vitro fertilization cycles despite transferring good quality embryos may also be considered. In such cases, the inability of the embryo to hatch and implant could be a contributing factor to previous implantation failures. Elevated levels of Follicle-Stimulating Hormone (FSH), indicating diminished ovarian reserve, might also prompt a recommendation. Women with high FSH levels sometimes have embryos with thicker zona pellucida, making assisted hatching a potential aid to implantation.
Potential Considerations and Outcomes
While assisted hatching aims to improve the chances of embryo implantation, it is important to understand the various considerations and potential outcomes. For certain patient groups, such as those with a thickened zona pellucida or repeated implantation failures, assisted hatching has been observed to improve implantation rates. Some studies suggest it can increase pregnancy rates in specific patients, though overall results can vary, and evidence on its effectiveness for all cases is mixed.
Despite its potential advantages, assisted hatching carries certain considerations. There is a slight possibility of damage to the embryo during the micro-manipulation process, which could make it unusable or reduce its viability. The technique requires expertise, as the embryo is susceptible to harm if not performed with precision. This manipulation could potentially weaken the embryo’s protective shell, exposing it to external factors in the uterine environment.
Another outcome associated with assisted hatching is a slight increase in the risk of monozygotic (identical) twinning. While the risk of twinning is already present in IVF, assisted hatching can further elevate the chance of identical twins. Some reports indicate a rate significantly higher than natural conception, ranging from 1.2% to 8.9% compared to a natural incidence of 0.42%. This heightened incidence is believed to be linked to the physical alteration of the zona pellucida, which might encourage the embryo to split.
Assisted hatching does not guarantee a successful pregnancy. While it addresses a specific hurdle related to embryo hatching, many other factors contribute to the overall success of an IVF cycle and subsequent implantation and pregnancy. The procedure is a supportive measure for specific cases, not a universal solution for infertility. Successful outcomes depend on numerous biological variables beyond the hatching process itself, including embryo quality, uterine receptivity, and overall patient health.
Making the Decision
The decision regarding the necessity of assisted hatching is highly individualized and requires thorough discussion with a fertility specialist. A specialist evaluates a patient’s unique medical history, specific circumstances, and the characteristics of their embryos to determine if the procedure is appropriate. This personalized approach ensures assisted hatching is considered only when it aligns with the patient’s specific needs and could potentially improve their outcomes.
Assisted hatching is not a routine procedure for all in vitro fertilization cycles; it is not a one-size-fits-all solution. Its application is reserved for cases where there are clear indications, such as those discussed previously, where the embryo’s ability to hatch naturally might be compromised. The fertility specialist carefully considers factors like maternal age, the thickness and quality of the zona pellucida, and any history of previous unsuccessful IVF attempts to tailor the treatment plan.
A comprehensive consultation allows the patient to understand the rationale behind the recommendation, along with the potential considerations and outcomes involved in the procedure. This collaborative decision-making process ensures the patient is fully informed and comfortable with the treatment plan, enabling them to make an educated choice. Ultimately, the choice to proceed with assisted hatching is made on a case-by-case basis, with the goal of optimizing the chances for a successful pregnancy in suitable candidates.