What is a trigger shot for IVF?
The trigger injection or ‘trigger shot’ as it’s also known, is a hormone injection. It is utilized in fertility treatment and usually consists of a hormone known as human chorionic gonadotropin, or u -HCG. It is HCG which triggers a follicle to mature and release the egg.
In maximum cases the trigger shot needs to be taken 36 hours earlier than egg collection, or an afternoon and a ½ day prior. The trigger shot timing is in synchrony with the improvement of follicles.It has to be completed when a good range of follicles have grown to their greatest size. Under or overdeveloped eggs have a decreased risk of conception success.
Alternative shots to U- HCG
- GnRH analog : Gonadotropin-releasing hormone agonist (GnRH-a) trigger has been used for the induction of final follicular maturation. It aims at ovulation with reduction of the OHSS risk. GnRH-a trigger stimulates FSH secretion in addition to LH surge. The advantage of this method is more maturity of the nucleus and the resumption of meiosis. Eventually it increases the number of Metaphase II oocytes. It is useful in patients under antagonist protocol only. Those under long agonist protocol won’t respond to it.
- Recombinant HCG – Recombinant fertility drugs are made in a laboratory using DNA technology. They are much similar to hormones made by the body in molecular composition. In the case of r-hCG, the lab-made hormone is similar to the body’s natural luteinizing hormone (LH). It is not recommended in people with primary ovarian insufficiency or those with very poor ovarian reserves. The fertility drugs in general may not be effective for these people. Since recombinant LH has a shorter half-life compared with hCG, its use also helps luteal support while potentially reducing OHSS risk.