What is a Trigger Shot in IVF?

Q: What is the cost of trigger injection in IVF?

The cost of a trigger injection in IVF can vary depending on the type of medicine, clinic, and the injection dosage.

Q: Do eggs grow after a trigger shot?

Yes. Small to medium follicles continue to grow and mature until they are ready for retrieval. This is important for collecting quality eggs for successful fertilisation.

Q: Is a trigger shot painful?

Trigger shots can be mildly uncomfortable but are not painful. However, the level of discomfort depends from person to person.

Q: What is the next step after the trigger shot?

After the trigger shot, the doctors wait for the eggs to mature. After maturation (mostly after 36 hours), doctors retrieve the eggs and combine them with sperm for fertilisation.

Reviewed by Dr. Nupur ,

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Last updated: March 19, 2025

Synopsis

Trigger shots for IVF, also known as trigger injections, are one of the most critical components of IVF. It is a hormonal injection used in fertility therapy, which contains a hormone called human chorionic gonadotropin, or hCG - which is produced by the placenta. It triggers the ovary to stimulate and produce eggs used in fertilisation.

The fertility doctor will tell all about the process, but even so, there must be enough questions about trigger shots. So, here we have discussed all the important aspects you may need to know to keep your mind at ease.

Understanding IVF Trigger Shots

Some know trigger shots as "pregnancy hormones." It works mostly like luteinising hormone (LH), which is produced in your pituitary gland and secretes right before ovulation. It is responsible for preparing eggs to mature and then release from the ovary and is a part of gonadotropin therapy, which is useful if patients:

Don't ovulate at all
Ovulation is considered weak
Looking to control ovulation as part of other procedures

Meiosis, in which your eggs lose half of their chromosomes (from 46 to 23), is likewise started by the trigger shot. This is crucial for the sperm cell's 23 chromosomes to unite with each egg for fertilisation.

When To Administer IVF Triggers Shot?

IVF professionals will use ultrasound imaging to track the size of your follicles. To gauge how you are reacting to the medications, they will also perform blood tests to assess your hormone levels. Your doctor will plan the trigger shot for around 36 hours before your egg retrieval once your follicles are the proper size. This enables egg retrieval before ovulation and gives the eggs time to develop.

Usually, the shot is administered at the clinic, but it can also be done at home. The shot can go into your fat tissue or your muscle. While you must do it once, it’s important when your doctor recommends it.

After the trigger shot, your eggs will undergo meiosis - as mentioned above. A doctor will arrange for your egg retrieval surgery to collect the eggs for laboratory fertilisation before their natural release. The embryo will be returned to the uterus for implantation after fertilisation. In general, the trigger shot is used in connection with other drugs to help with:

Anovulation (when your body doesn’t release eggs on its own)
Unexplained infertility (unknown cause of infertility)
In vitro fertilisation (for several infertility causes)

If you have had a trigger shot in the past, the doctor may adjust the dosage to combat any adverse effects.

How are Trigger Shots for IVF Timed?

After administering the trigger shots, ovulation takes place after 36 to 40 hours. In IVF, the doctor will monitor your ovaries through an ultrasound. This tells if the follicles are of the size as the doctor specifies (anywhere between 15-22 mm). This is usually between days 8 - 12 of your cycle.

After administering the shot, the egg retrieval process is scheduled within 36 hours. The eggs are fertilised using the partner’s or a donor’s sperm, which is then transferred between 3 and 5 days after retrieval or frozen (for later transfer).

Since the trigger shot contains hCG, it can give out false results (it might show positive, even if you’re not pregnant) if tested too soon. Experts recommend waiting for at least 2 weeks after the shot to take a pregnancy test, as it might take 10-14 days for the shot to leave your system. Also, if you are doing any other fertility treatment procedures, doctors may prescribe you a beta (initial) blood test to look for hCG.

Side Effects of Trigger Shots for IVF

Though trigger shots are generally safe, several side effects may vary depending on an individual’s health. One of the major risks is OHSS (Ovarian Hyperstimulation Syndrome), which happens due to excessive response to hormonal medications used for ovarian stimulation. OHSS is more common in PCOS patients. It causes swollen, painful ovaries, and in severe cases, it can lead to fluid accumulation in the abdomen, breathing difficulties, and blood clotting issues. Other signs include rapid weight gain (over 2 pounds a day).

Success Rates of Trigger Shots in IVF

The success rate of trigger shots is difficult to determine. That is mostly because it is used in combination with other drugs or procedures to treat infertility. The success of the trigger shot depends on several factors, such as - timing, medication type, ovarian response, etc.

Success Rates Based On hCG Vs. GnRH:

hCG Trigger Shots : This is a traditional choice that helps with ovulation and has high ovulation success and retrieval rates. However, there is a risk of Ovarian Hyperstimulation Syndrome in high responders.
GnRH Agonist Trigger Shot : These are often used for PCOS patients or those at high risk of OHSS, leading to similar egg retrieval rates. However, it requires the support of the luteal phase.

Conclusion

Make an appointment to speak with your doctor if you're interested to know more about the role of trigger shot in IVF and unsure if it might be beneficial for you. Once more, the shots are only administered during monitored cycles during which you are undergoing IUI, IVF, or timed intercourse.

You'll need to schedule frequent checkups to monitor the thickness of your uterine lining and the number of your follicles before using the trigger injections. Couples have experienced success using this strategy in conjunction with other reproductive treatments, even though it may seem like a lot of work.