A new way to prevent pregnancy without side effects

Non-hormonal gel proves effective at helping mucus block sperm.


Nearly half of the world’s pregnancies are still unplanned, reflecting a clear unmet need for contraception. Many women would prefer a nonhormonal, on-demand contraceptive that does not have the side effects of existing methods.

Now, scientists at KTH have come up with a new way to prevent pregnancy without side effects. They have developed a prophylactic gel from all-natural, non-hormonal ingredients to reinforce the cervical mucus barrier. It offers the first viable alternative to spermicides and contraception pills.

Compared to the untreated control animals, the gel reduced the number of uterine sperm by an average of 98% in tests on ovulating female sheep. Contrarily, it is known that birth control pills are between 91 and 99 percent effective.

Thomas Crouzier, a biopolymers researcher at KTH, said, “A single female sheep out of eight tested was found to have two sperm detected in its uterus after being treated with the topical gel. The results demonstrate the potential of an unprecedented approach to preventing unwanted pregnancies—one that blocks sperm by engineering mucus rather than killing sperm cells as spermicides do.”

“Mechanism taps into cervical mucus’ natural capacity as a barrier that isolates the vagina—where bacteria proliferate—from the uterus and upper reproductive tract. Cervical mucus also regulates the movement of sperm. Leading up to ovulation, the mucus barrier becomes a more selective gatekeeper, making exceptions for the passage of select sperm into the uterus.”

Scientists changed this dynamic by crosslinking mucin molecules with chitosan, a natural fibrous component frequently found in medical products, including hydrogels, meshes, and sutures. Mucin molecules are the proteins that give mucus its lubricating property. Cervical mucus is momentarily thickened by this mixture, making it more difficult for sperm to pass through.

Crouzier says“The chitosan was shown to have a similar effect in lab tests using human cervical mucus and sperm. It reinforced the mucus barrier quickly, with a reduction in sperm penetration after one-minute exposure and full sperm blockage after five minutes.”

“About 50 percent of women consider it important that their contraceptives do not contain hormones. This new mechanism of action has the potential to be very effective since it is reinforcing a barrier that already exists in the women’s reproductive tract.”

“Vaginal gels like this can be applied in seconds. We imagine a product like this should be usable seconds to a few hours before sexual intercourse. The effect could last hours but diminish over time as the mucus barrier is replaced naturally.”

Journal Reference:

  1. Ulrike Schimpf et al. Topical reinforcement of the cervical mucus barrier to sperm. Science Translational Medicine. DOI: 10.1126/scitranslmed.abm2417
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