What Is HCG Trigger Shot?

By Gwen Wark
medical syringe and ampoule on a white background. image by Petr Gnuskin from Fotolia.com

The hCG trigger shot is a dose of the hormone human chorionic gonadotropin, which normally is produced by the body after implantation of a fertilized egg into the uterine lining. This medication is delivered by injection and is timed to coincide with the final maturation of the ovarian follicles. When the hCG shot is delivered, those follicles release their eggs and a woman may become pregnant. The hCG trigger shot is used in fertility treatments such as timed intercourse and medicated cycles for intra-uterine insemination and in-vitro fertilization.

What the hCG Trigger Shot Contains

The hCG trigger shot is available by prescription and can be found pre-mixed or unmixed. The shot may be branded Ovidrel, Pregnyl, Profasi, Novarel or generic. A doctor will prescribe anywhere from 5,000 to 20,000 I.U. of the drug, depending upon the patient. It is very important to follow the doctor's instructions for mixing and administering this drug in order to ensure maximum fertility.

How the hCG Trigger Shot is Administered

An hCG shot may be administered at the doctor's office or at home. The timing of the shot is very important, as ovulation may occur anywhere from 12 to 48 hours after the injection. These hours will be the woman's peak fertile time, and any timed intercourse, egg harvesting or insemination needs to occur while the eggs are viable. The hCG trigger may be administered as a subcutaneous injection in the belly or thigh or as an intramuscular injection.

What to Expect from the hCG Trigger Shot

Once the shot is administered, the signal for final maturation of the eggs and ovulation occurs. Some women experience slight cramping and bleeding when ovulation occurs; this is quite normal and is not a cause for alarm. Timed intercourse or insemination takes place anywhere from 12 to 36 hours after the shot is given. Ideally, more than one insemination or round of intercourse may be used to increase chances of a viable egg being met by sperm.

Successful Cycles

If the hCG trigger successfully induces final maturation and ovulation, when combined with timed intercourse or insemination, this may result in fertilization of the egg. The hCG from the trigger shot remains in the urine for about seven to 10 days after the shot is administered, which means that home pregnancy tests may give a false positive after the trigger shot. A blood test to measure levels of hCG usually is conducted 14 or more days after ovulation, as these results should not be affected by the trigger.

Side Effects from the hCG Trigger Shot

Since hCG is produced by the body during pregnancy, the side effects of this drug are like those of early pregnancy. Nausea, breast tenderness, swelling and mild abdominal cramps are common side effects of the hCG trigger shot. The shot also may result in the release of more than one matured egg, which increases the risk of multiple births. These risks should be discussed with a doctor before the drug is administered, as selective reduction may be needed to ensure a healthy live birth.

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