Want to see an MRI of people having sex? Read on!
By Sara Twogood, MD
Reading the article “Magnetic resonance imaging of male and female genitals during coitus and female sexual arousal” in medical school was the first time I encountered a truly spicy scientific study.
The objective of the study (their words, not mine): “To find out whether taking images of the male and female genitals during coitus is feasible and to find out whether former and current ideas about the anatomy during sexual intercourse and during female sexual arousal are based on assumptions or on facts”
This is the way it went: A total of 8 couples participated. The female partner laid, back down, in the MRI machine for initial imaging of female anatomy. The male partner was then instructed to enter the machine and insert the penis into the vagina - but then not move. Images were taken. Viagra was used occasionally to help facilitate this, and only 1 male partner was able to obtain complete penetration without it. Then the male partner left and female partner masturbated until close to orgasm. Images taken. Then she masturbated to orgasm and 20 minutes later images were taken again.
Here is the result of the study:
In this “missionary” position, the erect penis almost always moved upwards at an angle of about 120 degrees (from the base of the penis to the tip) - almost parallel to the woman’s spine.
The penis filled the anterior part (called the fornix) of the vagina.
The uterus was raised on average 2.4cm over the female baseline.
The bladder configuration was changed – caused by the penile stretching of the anterior vaginal wall and the raised uterus
(Left side with the one of the actual MRI images, Right side image is same image, with anatomy labeled)
Another beloved image from this article - shown below – is an artist rendering of an erect penis inside the vagina - from a 1933(!) article (obviously not using an MRI).
It’s surprisingly close to the MRI images with one big exception - the penis is drawn in more of an “S” shaped. The actual MRI images show the penis universally more of a boomerang shape.
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Beyond a simple fascination in the study design itself, why are the findings important?
Because it shows in missionary position of sex, the boomerang shaped penis bounces off the anterior part of the upper vagina, adjacent to the bladder. In our “Troubleshooting pain with sex at home” digital lesson (get it here), one of the 20+ tips I give is to try having sex in different positions. In missionary position, the penis creates more pressure on the bladder and anterior part of the vagina. If there are bladder issues like UTIs or painful bladder syndrome, or pelvic floor dysfunction of the anterior muscles, having sex in this position can cause even more pain. If the female turns her body upside down but the male stays the same (often called doggy style) – the penis will bounce off the posterior part of the upper vagina near the rectum. This may feel A LOT better for some people. But for people who have endometriosis, bowel issues, or pelvic floor dysfunction of the posterior muscles, doggy style will feel WORSE. See how that works?
People often intuitively find different positions feel better– but when we can explain WHY that is with medical literature and findings, it gives even more reassurance and helps formulate a plan to optimize sexual wellness.
SOURCE: Schultz, Willibrord Weijmar; Pek van Andel, Ida Sabelis, Eduard Mooyaart. Magnetic resonance imaging of male and female genitals during coitus and female sexual arousal. British Medical Journal vol 319: 1596-1600. 18-25 Dec 1999