Women preparing for fertility treatment get a series of daily, sometimes uncomfortable, hormone shots to kick their ovaries into overdrive, but a review of previous studies suggests that one long-acting shot may work just as well.
In an analysis of four past studies, including over 2,300 women with infertility, researchers found the women were just as likely to get pregnant, and didn't have any more complications, when they got a single, long-acting dose of follicle-stimulating hormone (FSH).
For in vitro fertilisation, extra FSH is used to trigger the ovaries to grow and release multiple eggs, which are then fertilised outside the body and transferred to the uterus.
Jan Kremer from Radboud University Nijmegen Medical Center in the Netherlands, who worked on the study said: "Long-acting FSH (weekly injection) is a good and safe alternative to daily injections in the first week of ovarian stimulation for IVF."
Of the 2,335 women in the studies, 987 got daily FSH shots for a week and 1,348 had one long-acting shot at a range of doses, along with the usual course of other IVF hormone injections.
In studies that used the lowest dose of the long-acting hormone -- between 60 and 120 micrograms -- fewer women in the one-shot group got pregnant than in the daily FSH comparison group.
But at higher doses -- 150 to 180 micrograms -- pregnancy and birth rates didn't suffer, as 343 of every 1,000 women getting one long-acting shot had a baby, compared to 336 out of 1,000 in the daily-shot group.
The long-acting shot didn't seem to come with a higher risk of miscarriage, having twins or developing a pregnancy-related complication, including swollen ovaries.
The main advantage of the single shot is convenience, said Samuel Pang, medical director at the Reproductive Science Center of New England in Lexington, Massachusetts.
FSH shots are simple injections that women can give themselves, similar to insulin, but the process can still be difficult for some.
Pang, who wasn't involved in the new study, said: "In my mind, based on the studies that have been done and based on my own experience, it is a safe and effective product.
"The only caveat is it really needs to be used in well-selected patients."
Similarly to Kremer, Pang cautioned against using the long-acting shot in women who are unlikely to respond to the hormone, or those who may over-respond.