Clockwise from the top: FemCap, Oves & Prentif cervical caps
Self fitting cervical caps: Before I begin, a warning to do-it-yourselfers, self fitting of cervical caps is not a good idea and should be avoided if you plan to use one for contraception or flood insurance. That’s because:
- The FemCap maker says that a woman’s OB history is the primary indicator of her cap size. However, that is not always the case and in addition a severely anteverted or retroverted cervix will not allow the brim to seal properly against the vaginal walls and cause the cap to fail and the male partner to hit the brim. FemCap was approved for a continuous wearing interval of 48 hours.
- Self fitting a Prentif can be even more difficult because it suctions on the wall of the cervix itself and it comes in only 4 sizes so a significant percentage of women who wanted Prentif couldn’t be fitted. The wall of the cervix must be symmetrical and smooth so that the cavity rim can seal tightly around the entire circumference to develop the strong suction that holds the cap in place. Prentif hasn’t been produced for at least 5 years so availability is extremely limited and experienced fitters are very difficult to find. Prentif was approved for a continuous wearing interval of 48 hours.
- Oves, when it was available, over-the-counter in the UK, was the easiest to self-fit because you could buy a fitting kit with one of each of the three sizes and the dome was so soft that a woman could fairly easily fit herself, but it still required having a smooth cervical wall so the toothed rim could grip the cervix tightly. The dome membrane clings to the cervix by surface tension. Oves was approved in the EU for a continuous wearing interval of 72 hours.
Diving cervical caps while fertile: As I write this I’m CD3 and bleeding heavily so I’m wearing a Milex Omniflex for flow control for the five or six days of my period, unless I want menstrual sex, then I will switch to a flat spring so I can more fully enjoy the encounter and to minimize the possibility of under-thrusting. Returning readers know that my primary cervical barrier for contraception and flood insurance is an Oves cervical cap, but cervical caps can’t be worn effectively during menses.
Before I dive I always remove, empty, clean and reinsert my Oves cap so that the dome will be empty of cervical secretions when I enter the water. That way, when pressure collapses the dome, it won’t force the secretions out breaking the seal and cause the Oves to displace off my cervix. It’s necessary to stay well hydrated and I empty my bladder before diving because diving is very dehydrating. Water pressure squeezes fluids out of body tissues and into the kidneys. Even after emptying before entering the water the pressure will invariably cause me to need to urinate if I’m underwater for 30 minutes or longer and I end up peeing in the pool anyway. Severe dehydration can lead to loss of stamina, overheating and low blood pressure during a dive so going into a dive well hydrated is very important.
On the plus side for women divers dehydration due to diving minimizes menstrual flow and also fertile cervical mucus which is a good thing for divers wearing cervical caps for protection. From my own experience and discussions with other women divers the reduced uterine/cervical secretions while underwater seem to be a common side effect of diving for those of us of reproductive age. Emptying my cervical cap before each dive has worked well for me as I’ve never had a cap displace during an underwater sexual encounter. When I’m not fertile or menstrual and will be underwater for long intervals I take a 0.1mg tablet of Minirin (desmopressin acetate) an hour before I dive and then I don’t have to pee for about eight hours. It can react with antidepressants and pain meds but I’m not on any and have had no side effects with such a low dose.
The question: I had wondered what it felt like to have a cap displace, or float off my cervix, but until the multiplace hyperbaric chamber recently became available at Adolph’s training facility [I wrote about it in my post for July 1, 2012 entitled: The vacuum sealed cervix] I had no safe and effective way to see for myself what would happen if I dived my caps with spermicide and copious cervical secretions in the domes. So several weeks ago, when I was fertile this past cycle, I experimented with my cervical caps; 26mm silicone FemCap, 25mm latex Prentif and 26mm silicone Oves to see what happened when the domes collapsed from squeeze while filled with secretions. I wore each on a test dive in the hyperbaric chamber to simulate dives to 66 feet, three atmospheres (ATA), and how much that affected any thrust buffering the domes provide. The results are below.
A silicone rubber FemCap
The FemCap full dome test dive: After wearing my 26mm FemCap for two days, with a ¼ tsp of spermicide in the dome (as called for) and 36 hours of fertile cervical mucus (FCM) discharge in the dome I simulated a 66 foot dive in the hyperbaric chamber. Before proceeding I checked that the cap was properly in place by squatting and pressing upward on the strap and dome for more than 10 seconds to make sure the cap was correctly positioned with strong suction.
Then while lying on my back on one of the beds as the pressure increased and I worked to equalize the pressure in my ears and sinuses I inserted two fingers in my vagina to feel any changes in the dome due to squeeze. As I expected the pressure forced my cervix deeper into the dome then the dome collapsed filling any remaining void between the top and my cervix. At 15 feet it wasn’t painful just a lot of pressure, but as I passed the 2 atmosphere depth, 33 ft., the pressure became very uncomfortable then disappeared entirely as I felt the spermicidal gel and fertile cervical mucus gushing out between the brim and my vaginal walls as the cap was floated off my cervix. It was just as I thought; as the cervix fills the dome spermicide and cervical secretions were squeezed out by the pressure breaking the seal and dislodging the cap. A dislodged FemCap provides no contraceptive protection. Only the spermicide remains as a contraceptive barrier and any thrust buffering a properly placed FemCap can provide may disappear unless the cap is forced back on to the cervix by a thrusting penis.
A pair of 22mm latex Prentif cavity rim cervical caps:
The Prentif cavity rim cap test dive: Two days after FemCap I tested my 25mm Prentif cap. Prentif is no longer made, but was very popular in Europe where caps were available long before the Prentif was approved by the FDA 1n 1988 for use in the U.S. so there are women both in the U.S and Europe still using them.
I had applied spermicide in the dome and worn my Prentif for 36 hours while fertile so that it would have plenty of FCM in the dome before I went into the hyperbaric chamber and increased the pressure to three ATA. Again, while lying on my back on one of the beds as the pressure increased and I worked to equalize the pressure in my ears and sinuses I inserted two fingers in my vagina to feel any changes in the dome due to squeeze. As I expected the pressure forced my cervix deeper into the dome then the dome collapsed filling any remaining void between the top and my cervix. But the dome of the 25mm Prentif is deeper than the FemCap dome and the pressure of having my cervix squeezed into the dome was more uncomfortable and then at 30 feet the dome collapsed, the cavity rim filled spermicide and FCM and the suction disappeared as the secretions were pushed out under the base of the rim and the Prentif floated off. It was still on my cervix, but not firmly attached and if I’d been having dive-sex with a bareback partner when it popped off I would have been in trouble and would have needed to use emergency contraception. A Prentif has some thrust buffering value. The tab on the shoulder of the cavity rim, to aid in screwing the cap on to the cervix, can hurt a partner so should be rotated to the back.
A pair of Oves silicone rubber cervical caps
The Oves cap test dive: Several hours after I removed my Prentif cap and my cervix had returned to normal I inserted my 26mm Oves cap and screwed it down tight on my cervix. At that point in my cycle I was two days before I ovulated the most fertile part of my cycle. I let the FCM build up again for 36 hours then as I had done for the other tests while lying on my back on one of the beds as the pressure increased and I worked to equalize the pressure in my ears and sinuses I inserted two fingers in my vagina to feel any changes in the dome due to squeeze. Because the dome is so thin and soft the FCM in the cap was squeezed out of the dome and the cap floated off at about 15 feet, less than the depth of an encounter pool. It sent a chill down my spine as I realized that wearing an Oves with a days worth of FCM in the dome on a dive-sex encounter would quite possibly result in an unintended pregnancy.
Not that I wear my Oves that way as I mentioned earlier, but I’d come to think of being invincible, well at least impregnable, while wearing Oves so it was sobering – though not totally unexpected - to have it proven that If I forget to empty, clean and then reinsert my Oves before a dive during my fertile days then even on a shallow dive I would be setting myself up for trouble. Fortunately for me the dehydration effect of diving plays an important role in limiting the production of FCM so that the effectiveness of diving Oves is not compromised when the dome is emptied immediately before a dive. The Oves cap provides no thrust buffering.
Conclusions: My experiments in the hyperbaric chamber show that a cervical cap with spermicide and fertile cervical mucus in the dome when worn for dive-sex will displace anywhere from a depth of 15 to 30 feet. The domes of FemCap and Prentif have a crush depth of about 30 feet at which point even when worn dry (w/o spermicide) they become extremely uncomfortable to wear and in my case would cause me to break off a dive to return to shallower water or the surface. FemCap shouldn’t be worn w/o spermicide so I think it shouldn’t be worn for dive-sex except at depths of less than 15 feet. A Prentif with an excellent fit can be effectively worn w/o spermicide so could probably be worn for a sexual encounter down to its crush depth where it becomes extremely uncomfortable at about 30 feet. Oves, emptied before a dive, can be worn to any depth because the dome is already collapsed and clinging to the cervix so there are no voids to create squeeze.