Most women want to become pregnant as naturally as possible and women facing infertility are no exception. To improve treatment options for infertility, doctors developed the “Slow Release Insemination” system. This process mimics the natural process of fertilization which typically takes place over the course of several hours– or even days– following intercourse. Here are some things you need to know.

What is Slow Release Insemination (SRI)?

It’s a procedure where semen is gradually introduced into the uterus near a fallopian tube over a period of three to four hours.

Why is Slow Release Insemination thought to be “more natural” than Intrauterine Insemination (IUI)?

In a natural setting following intercourse, sperm gradually make a long journey through the uterus towards the fallopian tubes, all hoping to be the father of an adorable little egg. What most people don’t realize is that it can take a sperm up to 72 hours to reach an egg and successfully fertilize it.

Likewise in SRI, a small number of sperm are continuously released into the uterus over a long period of time. Not only does this extend the window for potential fertilization, it more closely fosters the journey of the sperm towards the egg than traditional IUI methods.

Is Slow Release Insemination more effective than Intrauterine Insemination?

In a report published in May 2020, researchers found that of the 183 women participating in the study, 19 became pregnant via SRI versus 14 who became pregnant via IUI. In a 2017 study of 51 women, 7 became pregnant through SRI while 3 became pregnant through IUI. The researchers stress that a lot more work needs to be done to see if these slightly elevated rates are truly reliable. They also stress that these increased chances of pregnancy are primarily for women aged 35 years or younger.

Is Slow Release Insemination right for you?

Contact your fertility clinic and ask about your doctor’s familiarity and experience with this technique. You never know; this could be the start of your new family!


“Pregnancy rates after slow-release insemination (SRI) and standard bolus intrauterine insemination (IUI) – A multicentre randomised, controlled trial” –

“The effect of slow release insemination on pregnancy rates: report of two randomized controlled pilot studies and meta-analysis” –

“Slow release intrauterine insemination versus the bolus technique in the treatment of women with cervical mucus hostility” –