Magnetic Resonance Imaging (MRI) Of Sexual Intercourse: Second ...
Journal of Sex & Marital Therapy, 28(s):63–76, 2002
Copyright © 2002 Brunner-Routledge
0092-623X/02 $12.00 + .00
Magnetic Resonance Imaging (MRI)
of Sexual Intercourse: Second Experience
in Missionary Position and Initial Experience
in Posterior Position
A. FAIX
Department of Urology, CMC Beau Soleil, Montpellier, France
J. F. LAPRAY
Department of Radiology, CMC Beau Soleil, Montpellier, France
O. CALLEDE
Department of Radiology, CMC Beau Soleil, Montepellier, France
A. MAUBON
Department of Radiology, CMC Beau Soleil, Montepellier, France
K. LANFREY
Department of Urology, CMC Beau Soleil, Montepellier, France
Our objective was to confirm that it is feasible to take images of the
male and female genitals during coitus and to compare this present
study with previous theories and recent radiological studies of the
anatomy during sexual intercourse. Magnetic resonance imaging
was used to study the anatomy of the male and female genitals
during coitus. Three experiments were performed with one couple
in two positions and after male ejaculation. The images obtained
confirmed that during intercourse in the missionary position, the
penis reaches the anterior fornix with preferential contact of the
anterior vaginal wall. The posterior bladder wall was pushed for-
ward and upward and the uterus was pushed upward and back-
ward. The images obtained from the rear-entry position showed for
the first time that the penis seems to reach the posterior fornix with
preferential contact of the posterior vaginal wall. In this position,
the bladder and uterus were pushed forward. A different preferen-
tial contact of the penis with the female genitals was observed with
each position. These images could contribute to a better understand-
ing of the anatomy of sexual intercourse.
Address correspondence to A. Faix, CMC Beausoleil, 119 Avenue de Lodeve, 34070
Montpellier, France. E-mail: a.faix@languedoc-mutualite.fr
63
64
A. Faix et al.
Leonardo da Vinci depicted “the copulation” in 1493 (Clark & Pedretti, 1968) ,
after which, we had to wait until 1949 for the first study of the interaction of
male and female human genitals during coitus (Dickinson, 1949; Figure 1) . A
glass test tube, as big as an erect penis, was inserted into the vaginas of the
female subjects, who were sexually aroused by clitoral stimulation. This guided
Dickinson in the formulation of his anatomical suppositions. As you can see
from Figure 1, in the missionary position, the penis reaches the posterior
fornix. In the 1960s, Masters and Johnson (1966) carried out their assess-
ments with an artificial penis that could mechanically imitate natural coitus
and allow direct observation. The most remarkable observation regarding
the anatomical vaginal changes was the backward and upward movements
of the anterior vaginal wall called “vaginal tenting.” In the 1990s, Zwang
(1990) imagined, in a theoretical diagram, that the penis preferentially reaches
the posterior fornix in any coital position (see Figure 2). In 1992, Riley and
Riley published an ultrasound study of copulation that investigated the be-
havior of a new intravaginal barrier contraceptive device during the penile
thrusting in normal human coitus. Although the images were relatively poor
quality and were unavailable for viewing, the conclusions were interesting.
In 9 out of 10 couples, there was an indentation and stretching of the ante-
rior wall of the vagina and no direct impact on the posterior wall in any
coital position. However, in 2 out of 9 couples in rear-entry position, there
was an impact on the cervix. Schultz, VanAndel, Sabelis, and Mooyart (1999)
carried out a study by MRI on 8 couples and 3 single women. In 3 out of 4
couples with complete penetration, there was a preferential contact of the
penis with the anterior fornix and vagina wall. In the fourth case, the uterus
seems to be retroverted, however, we do not see a magnetic resonance
imaging (MRI) image of the female pelvis prior to penetration. The last part
of this study involved observing clitoral stimulation in 3 single females. There
was a lengthening of the vagina but no increase in the uterine volume. Faix
FIGURE 1. Dickinson’s (1949) diagram
Magnetic Resonance Imaging of Sexual Intercourse
65
FIGURE 2. Zwang (1990) diagram
(2001) also carried out an MRI study in which he showed that in the mission-
ary position, there was preferential contact of the penis with the anterior
fornix and the anterior wall of the vagina. As can been seen from these
theoretical and radiological studies, there were contradictions concerning
the preferential impact point of the penis, according to the position. Except
for the ultrasound study by Riley & Riley (1992), there was no live study of
coitus in the two natural positions (missionary or rear entry). MRI had al-
ready been used as a diagnostic tool to study erectile impotence. The obvi-
ous advantage of MRI is the production of safe images with precise anatomi-
cal details that are clearer than those obtained from ultrasonography. The
aim of the current study was to confirm the first MRI study of coitus and the
observe the anatomical differences between the two different positions, us-
ing the same couple.
METHODS
The couple have a normal private life and were recruited by personal invita-
tion. They both signed an informed-consent form. This project was approved
by the ethical committee. The male measures 180 cm and weighs 80 kg. His
erection is 16 cm long and looks normal (no congenital curvature). The
female measures 167 cm and weights 52 kg. Her gynecological examination
is normal and she is parous (one normal delivery in 1995) . They have a
normal sexual life, with sexual intercourse occurring usually 4 times a week.
66
A. Faix et al.
They have no erectile or dysorgasmic problems. The couple were guaran-
teed confidentiality, privacy, and anonymity.
The details of the MRI machine were:
General Electric 1 Tesla
Single shot fast spin Echo (SSFSE)
Static T2 weighted sagittal sequences on the midline
TE (time echo) = 18
TR (time repetition) = 6000 ms
Matrix = 256–192
The couple were invited to come for a scan at night, when the equipment
was available. The volunteers were shown the equipment in the two rooms.
The experimental procedure was explained and the investigators left the
imaging room. The research team sat behind the scanning console and screen.
An improvised curtain covered the window between the two rooms; the
intercom was the only means of communication. The internal diameter of
the tube was 60 cm, which, once in position, leaves a space of only 3 cm
between the back of the male and the top of the tube.
There were four sessions. The first session, without penetration, was to
initialize the machine parameters. The female was asked to ensure that her
urinary bladder was as empty as possible. In the second session, the couple
began sexual intercourse outside the MRI tube (45 min after the male had
taken 50 mg of Viagra) . They then lay in position on the ramp: The female
lying on her back with her legs slightly open and the male lying on top of
her (missionary position). The team checked the position on the midline
through the different slices to guide the couple during coitus. In the third
session, the couple changed positions, with the female lying on her abdo-
men, bottom slightly turned upward, and the male on top on her (rear-entry
position). In the fourth and last session, the couple again performed the
missionary position to attempt to reach orgasm. Only the male succeeded.
Unfortunately, because of the increased movement within the tube, the im-
ages of the male ejaculation were not available; there were only images
available immediately after ejaculation. During the three sessions with pen-
etration, the female experienced preorgasmic sensations but no real orgasm.
Each session took about 15 min. In the radiological evaluation, we examined
and measured the pubococcygeal line, which links the pubis and the coc-
cyx, the axis of the penis outside and inside vagina, and the anatomical
connections between the penis and the female anatomical structures.
RESULTS
In spite of the experimental conditions, the couple did not experience any
difficulty having intercourse in the MRI scan. In the first session without
Magnetic Resonance Imaging of Sexual Intercourse
67
penetration (the female on the left and the male on the right side), the axis of
the vagina is roughly parallel to the pubococcygeal line, and has a moder-
ated anterior convexity that is parallel to the elevator ani (see Figures 3 and
4) . The vagina axis is about 140° between the upper and the lower part (see
Figure 5) . The anterior vaginal length (to the anterior fornix) is 7.5 cm, and
the posterior vaginal length (to the posterior vaginal fornix) is 11 cm. The
cervix-pubis distance is 4.5 cm, and it is 2.5 cm above the pubococcygeal
line. The uterus axis is about 30° compared to the horizontal line and 60–80°
relative to the main vaginal axis. It is normally anteverted (tilting forward), its
length is 8 cm, and its width is 4.5 cm (see Figure 5).
In the second session (missionary position with the male on the left and
the female on the right) , the penis (corpus cavernosum) has a high signal in
T2 weighted sequence (see Figure 6) . There is a posterior shift of the uterus
and a preferential contact of the penis with the anterior vaginal fornix and
wall, the posterior bladder, and the urethra (which is not really visible) through
Halban’s fascia (see Figure 7). The complete penis takes the shape of a
boomerang, and there is an angle between the root of the penis and the
pendulous part of the erect penis, which has moved upward by about 110
degrees. The length of the pendulous part inside the vagina is about 13 cm;
1.5 cm remains outside, and the length of the root is 11 cm. There is an
FIGURE 3. MRI first session without penetration
68
A. Faix et al.
FIGURE 4. MRI first sessions diagram. (1) Male bladder; (2) Male pubis; (3) Female bladder;
(4) Female pubis; (5) Sacrum; (6) Uterus; (7) Vagina; (8) Cervix; (9) Elevator ani.
FIGURE 5. MRI first session, angles and lengths; (1) Vagina axis: 140º; (2) Uterus axis compared
to the vagina axis: 60–80º; (3) Uterus axis compared to the horizontal line: 30º. Lengths: (1)
uterus lengthening: 8 cm; (2) uterus width: 4.5 cm; (3) Anterior vaginal lengthening: 7.5 cm;
(4) Posterior vaginal lengthening: 11 cm; (5) Cervix - Pubis: 4.5 cm, (6) Cervix - Pubococcygeal
line: 2.5 cm.
Magnetic Resonance Imaging of Sexual Intercourse
69
FIGURE 6. MRI second session (missionary position)
increase in the length of the vagina, which has almost doubled and become
the same length as the penis. Therefore, there is a significant amount of
stretching, with an increase from 7.5 cm to 13 cm (75%) , and a vaginal
tenting of the anterior fornix. The glans of the penis is closed to the corpus
uteri and 4 cm above the cervix. The female bladder is almost empty. There
is an increase of the anterior convexity of the vagina and preferential contact
with the anterior fornix and the bladder, which is pushed forward and up-
ward. The uterus is raised by 2.5 cm and there is a forward movement when
FIGURE 7. MRI second session diagram. (1) Male bladder; (2) Female bladder; (3) uterus;
(4) Anterior fornix; (5) Posterior vaginal wall (6) Erect part of the penis inside vagina; (7)
Male pubis; (8) Root of the penis; (9) Testis; (10) Female pubis.
70
A. Faix et al.
FIGURE 8. MRI second session, angles and lengths. (1) Angle 110º; (2) Angle 50º; (3) Angle
60º; (4) 13 cm; (5) 11 cm; (6) 8 cm; (7) 4 cm; (8) Uterus pushed upward and backward,
bladder pushed upward and forward; (9) Vaginal tenting of the anterior fornix.
compared to the pubococcygeal line. The uterus axis to the horizontal line is
60° and is turned slightly upward. Compared to the vagina axis, the uterus is
at an angle of 25° (see Figure 8). The vaginal axis changes from 140´° to 50º
because of the anterior vaginal tenting. The size of the uterus is unchanged
despite the female’s preorgasmic sensations.
In the third session (rear-entry position) , there is preferential contact of
the penis with the posterior wall of the vagina and probably with the poste-
rior fornix as well as the rectum through the vaginal wall (see Figures 9 and
10) . The penis has roughly the same shape and the same angle (100°) . The
length inside the vagina is 13 cm, which is the same as in the missionary
position (see Figure 11) . There is no increase of the vaginal length to match
the depth of penetration, but there is a vaginal tenting of the posterior fornix.
The stretching of the posterior vaginal wall is less significant (11 to 13 cm,
20%) . There also is a decrease of the vaginal anterior convexity, which be-
came concave, produced by the glans reaching the posterior fornix. The
corpus uteri can be seen very clearly but is not exactly sagittal; therefore, we
Magnetic Resonance Imaging of Sexual Intercourse
71
FIGURE 9. MRI third session (rear entry position )
cannot see with certitude the cervix, which seems to be situated laterally
compared to the penis and corpus. But, it is possible that it may have been
squashed flat at the bottom of the posterior fornix. The uterus is swung
down by 4 cm from its axis, which is now almost horizontal (see Figure 11).
The main problem with these images is understanding the behavior of the
cervix because of the poor visibility of the fornix. However, the glans ini-
tially pushes the cervix upward and swings the uterus downward. Thereaf-
ter, it seems to reach the posterior fornix so that in the rear-entry position,
the bladder and uterus were pushed forward. Compared to its shape in the
missionary position, the uterus is more deformed and has a completely dif-
ferent axis. The changes in length and axis of the different structures are
summarized in Table 1.
FIGURE 10. MRI third sessions diagram. (1) Male bladder; (2) Female bladder; (3) Uterus;
(4) Posterior fornix; (5) Anterior vaginal wall; (6) Erect part of the penis inside vagina (7)
Male pubis, (8) Female pubis; (9) Testis.
72
A. Faix et al.
FIGURE 11. MRI third sessions, angles and lengths. (1) 13 cm; (2) 10º; (3) Penis axis =
Vagina axis; (4) Uterus pushed downwards and forwards, cervix upwards?; (5) Vaginal tenting
of the posterior fornix (cervix no depicted)
In the fourth and last session, again in missionary position, the sperm
can be seen with a high signal T2 around the cervix a few minutes after male
ejaculation (penis is still inside the vagina; Figures 12 and 13).
DISCUSSION
The research team took 2 years to complete this study and came up against
various difficulties and obstacles. But is this experience representative of the
normal physiology of sexual intercourse? The couple replied that it was
comparable even under the particular conditions—with preorgasmic sensa-
tions for the female in both positions and an ejaculation with orgasm for the
male in the missionary position.
The hypothesized anatomy of human coitus, as drawn by Leonardo da
Vinci in 1493, by Dickinson (1949) , and by Zwang (1990) could be tested
with MRI. According to our study, there is preferential contact with the ante-
rior fornix in missionary position and with the posterior fornix in rear-entry
Magnetic Resonance Imaging of Sexual Intercourse
73
TABLE 1. Comparative Table According to the Position
Before penetration Missionary position
Rear-entry position
Vagina
Axis
140°
50°
180°
Anterior vaginal length
7.5 cm
13 cm
Posterior vaginal length
11 cm
13 cm
Uterus
Axis/horizontal line
30°
60°
10°
Length
8 cm
8 cm
?
Width
4.5 cm
4.5 cm
4.5 cm
Translation
Pushed up &
Pushed down &
backward
forward
Bladder
#empty
Pushed up &
Pushed forward
forward
Penis
Erect part
13 cm
13 cm
Impact point
Anterior fornix
Cervix and
posterior fornix
Shape
Boomerang
Boomerang
position. The images showed that during intercourse, whatever the position,
the penis is never straight, as drawn by Leonardo da Vinci and Zwang, but
takes on the shape of a boomerang and not of an S, as described by Dickinson.
These three authors clearly underestimated the size of the root of the penis.
The boomerang shape of the erect penis could be the explanation for the
anatomical differences between the theoretical diagrams and those obtained
by our MRI study. We also must note the differences with the conclusions of
FIGURE 12. MRI fourth session (missionary position, immediately after ejaculation) .
74
A. Faix et al.
FIGURE 13. MRI fourth session diagrams (1) Sperm; (2) Male bladder; (3) Female bladder;
(Uterus; (5) Cervix; (6) Anterior fornix; (7) Posterior fornix.
the ultrasound study by Riley and Riley in 1992; even in rear-entry position,
there was preferential contact of the penis with the cervix for only two out of
nine couples. However, self-scanning, the poor quality of the images, and
the unavailability of these make correct interpretation difficult, perhaps even
impossible. As for the MRI study performed by Schultz et al. (1999) , in one
out of four couples, the penis reaches the posterior fornix, however, the
uterus seems to be retroverted, and we do not have an MRI image of the
female pelvis prior to penetration.
In light of these radiological studies, must we conclude that female
genital stimulation has a strong positional influence and is dependent on the
coital position of the vaginal and uterus axis? We could suggest that, accord-
ing to these anatomical facts, there possibly are two types of vaginal or-
gasms, one from preferential stimulation of the anterior vaginal wall (G-
spot?; Graffenberg, 1950) and one from deeper preferential stimulation of
the posterior wall of the vagina and cervix (and perhaps the posterior fornix?)
Histological studies (Hilleges, Falconer, Ekmon-Orderberg, & Johanson, 1995;
Krantz, 1985) and immunohistochemistry have shown that the anterior wall
of the vagina has denser innervation that the posterior wall. This is sup-
ported by clinical studies and research of intravaginal sensitivity to electric
stimuli (Alzate & London, 1984; Hoch, 1986; Schultz, Van de Wiel, Klatter,
Sturm, & Nauta, 1989) . Obviously, we need to be very careful about this
artificial dichotomy of the vaginal orgasm before other studies are conducted,
because our study was carried out using only one couple and the deductions
are hypothetical. Concerning the female internal genitals (Levin, 1998) and
the changes during intercourse (thickening of the vaginal wall due to vasodi-
latation, lubrication, lengthening and widening of the vagina and urethra,
Magnetic Resonance Imaging of Sexual Intercourse
75
changes in axis, position and size of the uterus), because of the resolution of
our equipment, we are only able to see the movements of the uterus and the
bladder according to the coital position. We also can observe the lengthen-
ing of the vagina and its volume, which is initiated by the erect pendulous
part of the penis. In contrast to the findings of Masters and Johnson (1966)
and Schultz, our images did not show an increase in the size of the uterus
even when the female have preorgasmic sensations.
CONCLUSION
Initially, the aim of the study was to “copy” the genius Leonardo da Vinci.
We showed that an MRI scan of sexual intercourse in two positions is fea-
sible and artistic but not as artistic as the images drawn by Da Vinci. In our
study of one couple, during intercourse, the erect penis takes on the shape
of the boomerang and is not straight or S shaped. Depending on the coital
position, the preferential impact of the glans seems to differ, as does the
behavior of the cervix and the uterus. There is, therefore, a higher probabil-
ity of a difference in stimulation, thus the pleasure felt as a result may also be
different. Obviously, we need to continue with further studies, which are
planned in different couples. However, it is important to remember that,
whatever the position, female arousal depends on various psychological
aspects, which are probably different for each woman. MRI could be a new
tool to assess the physiology of sexual intercourse.
REFERENCES
Alzate H., & London, M. L. (1984) . Vaginal erotic sensitivity. Journal of Sex & Marital
Therapy, 10, 49–56.
Clark, K., & Pedretti, O., (1968) . The drawings of Leonardo da Vinci in the collection
of Her Majesty the Queen at Windsor Castle. London: Phaidon.
Dickinson, R. L. (1949). Human sex anatomy, A topographical hand atlas (2nd ed.).
London: Braillier, Tindall, and Cox.
Faix, A. (2001). Magnetic resonance imaging of sexual intercourse: Initial experi-
ence. Journal of Sex and Marital Therapy, 27, 475–482.
Graffenberg. (1950). The role of urethra in female orgasm. International Journal of
Sexology A current appraisal, 3, 145–148.
Hilleges, M., Falconer, C., Ekmon-Orderberg. G., & Johanson, O. (1995). Innervation
of the human vaginal mucosa as revealed by PG P 9.5 immunochemistry. Acta
Anatomica, 153, 119.
Hoch. (1996) . Vaginal erotic sensitivity by sexual examination. Acta Obstetrics
Scandinavia, 5, 767–773.
Krantz , K. E. (1985). Innervation of the human vulva and vagina. Obstetrics and
Gynaecology, 12, 382–396.
76
A. Faix et al.
Levin, R. J. (1998) . Sex and the human female reproductive tract :what really hap-
pens during and after coitus. International Journal of Impotence Research, 10
(suppl. 1), 14–21.
Masters, W. H., & Johnson, V. E. (1966). Human sexual response. Boston: Little,
Brown .
Riley A. J., Lee, W.. & Riley, E. J. (1992) . An ultrasound study if human coitus. In W.
Bezemer, P. CohenpKettenis,K. Slob, N. Van San-Sehoonts (Eds.) , Sex matters
(pp. 29–36) . Amsterdam: Elsevier.
Schultz W. G. M., Van Andel, P., Sabelis, I., & Mooyart, E. (1999). Magnetic reso-
nance imaging of male and female genitals during coitus and female sexual
arousal. British Medical Journal, 319, 1596–1600.
Schultz , W. G. M , Van de Wiel , H. B. M., Klatter, J. A., Sturm, B. E., & Nauta, J.
(1989). Vaginal sensitivity to electric stimuli, Theoretical and practical implica-
tions. Archives of Sex Behavior, 18, 87–95.
Zwang, G. (1990). Abrégé de sexologie. Paris: Edition Masson.
ALL IMAGES AND DIAGRAMS ARE UNDER COPYRIGHT IN MY NAME. I AGREE THEY CAN
BE PUBLISHED PURELY FOR THE PURPOSES OF THIS ARTICLE.
