Introduction
Assisted hatching is a laboratory procedure that is done along with in vitro fertilization (IVF).IVF involves the mixing of sperms with eggs in the laboratory. When sperm penetrates the egg, it is considered to be fertilized. Fertilized eggs are observed for 3 to 6 days as they divide and grow into embryos. The best embryo can then be placed inside the womb of women or it can be frozen for future use. When the embryo is developing, it gets surrounded by cells that make a protective shell (zona pellucida). Embryo naturally breaks out of this shell for growth. Sometimes, in the indicated cases, the doctor may ask the embryologist to create a small crack in the outer covering of an embryo just before the embryo is placed inside the womb. Assisted hatching is done with the view that this might help in the expansion of the embryo, implantation into the uterine wall, and hence leading to a pregnancy.
What are the indications of assisted hatching?
The most common indications of assisted hatching with in vitro fertilization are
1. Age -women is older than 37 years.
2. Woman with poor ovarian reserve: low AMH levels/ low AFC (antral follicle count)/ high levels of follicular stimulating hormone on day 2/3 of periods.
3. Women with low AMH levels.
4. Women with low antral follicular count.
5. Women with poor-quality embryos.(excessive fragmentation or slow rate of cell division)
6. Zona factor-cases with thick outer shell (zona pellucida)
7. One or more previous failed IVF cycles.
How is assisted hatching done?
The outer shell of the embryo is artificially weakened by making a small hole in the zona pellucida. This can be done by different methods like using an acid solution called Tyrode’s solution or by using a laser.
Can assisted hatching cause problems in embryos or pregnancy?
Sometimes assisted hatching can cause damage to the embryo, but although it is rare when meticulously performed by a trained embryologist. This can make the embryo unusable. There are some studies that show that the risk of identical twins is slightly increased in cases where assisted hatching is applied, however, there is insufficient evidence to definitely conclude that AH is associated with monozygotic twinning.
It must be meticulously performed by a trained embryologist.
Does assisted hatching improves pregnancy rates?
In an unselected/general population, live birth rates are not significantly different between embryos that have undergone AH vs those that have not, HOWEVER, in patients with a poor prognosis data is mixed and there seems to be benefit in a subset of patients who have to be carefully selected by an experienced clinician. Pregnancy rates for IVF procedures with assisted hatching have been shown to be higher than for IVF without assisted hatching in some published studies. Apparently, this benefit is not seen in all IVF programs.
Dr Megha Gupta
MBBS, DNB, FMAS, PGDMLS, MICMCH.
Fellow of reproductive medicine.
Craft Hospital and research center,
Kodangallur, Kerela.
