What MRI studies have measured uterine volume changes before, during, and after female orgasm?
Executive summary
Magnetic resonance imaging (MRI) studies that directly measured uterine volume around female orgasm are limited; the widely cited pelvic MRI series by van Andel and colleagues (published in The BMJ, 1999) is the principal MRI dataset and it found no measurable increase in uterine volume during sexual arousal or at orgasm, contradicting the mid‑20th century clinical claim of a 50–100% uterine volume rise (Masters and Johnson) [1] [2]. Other MRI reports and reviews repeat and reinforce that lack of uterine enlargement while documenting other pelvic shifts (anterior vaginal wall lengthening, uterine displacement) and note methodological limits that constrain firm physiological generalizations [3] [4] [5].
1. The landmark MRI “sex in the scanner” project and its uterine-volume finding
Between 1991 and 1999 investigators acquired midsagittal pelvic MR images of people during coitus and during self‑stimulation and reported experiments on a small cohort (thirteen experiments involving eight couples and three single women); these images showed pre‑orgasm anterior vaginal wall lengthening and uterine displacement but explicitly found no increase in uterine volume during arousal or at orgasm (images were taken pre‑orgasm and about 20 minutes after orgasm) [1] [6] [7].
2. How that conclusion contrasts with Masters and Johnson’s older observations
Masters and Johnson in the 1960s, using speculum observation and bimanual palpation in “bedroom” experiments, described a backward‑and‑upward vaginal tenting and reported a 50–100% greater uterine volume during female sexual arousal that returned to baseline 10–20 minutes after orgasm; the MRI team explicitly framed their work as testing those prior assumptions and reported results at odds with the large uterine‑volume claim [2] [1].
3. What MRI actually measured instead — displacement, tenting, and soft‑tissue changes
The MRI data documented a roughly 1 cm lengthening of the anterior vaginal wall in the pre‑orgasmic phase and an upward displacement of the uterus within the pelvis — observable positional and soft‑tissue changes rather than an overall volumetric enlargement of the uterine corpus [1] [3] [4]. Radiologic commentators have emphasized that MR images are “beautiful” and feasible for this work but that the main pelvic changes visible were anatomical rearrangements and vascular engorgement in vulvovaginal tissues rather than a measurable uterine volume increase [7] [8].
4. Other measurements related to uterine activity: pressure versus volume
Separate physiologic “bedroom” studies using manometry—not MRI—reported intrauterine pressure spikes during orgasm (for example, increases to +40 cm H2O with rapid fall thereafter), a finding relevant to uterine contractility and potential sperm transport but not a direct measure of uterine volume; reviewers note these pressure experiments have been rarely repeated because they are complex and invasive [9]. Functional MRI brain studies have explored central correlates of orgasm but do not substitute for pelvic volumetric MRI data [10] [5].
5. Strengths, limitations, and the evidentiary bottom line
MRI provided the first noninvasive moving pictures of coitus and female sexual arousal and demonstrated specific pelvic tissue movements with small sample sizes and significant technical constraints (long acquisition times, motion artifacts, and limited temporal resolution in early 1.5‑T systems), which the authors and subsequent reviewers cite as important caveats; within these constraints the van Andel/Schultz et al. MRI series remains the primary MRI evidence and reports no uterine volume increase during arousal or at orgasm, while earlier clinical observations and pressure studies report other, plausible physiological changes that MRI did not corroborate or was not designed to measure [7] [5] [2] [9].