Science Vs The Great Mysteries of Sex with Mary Roach
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Mar 26, 2026 
Mary Roach, best-selling science writer known for probing quirky, taboo human biology, joins to explore sex research history and oddball methods. Short, lively segments cover the female orgasm and the 'upsuck' idea, bizarre lab tools and pioneers' techniques, pig insemination practices in Denmark, and jaw-dropping ultrasound discoveries like a masturbating fetus.
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Masters And Johnson Found No Evidence For Upsuck
- Masters and Johnson tested the 'upsuck' hypothesis by using radio-opaque artificial semen and X-rays during orgasm and found no evidence of sperm being sucked toward the uterus.
- They also noted uterine contractions are expulsive rather than sucking, contradicting long-held beliefs about orgasm aiding conception.
Small Studies Hint At Upsuck But Evidence Is Inconclusive
- Recent small studies show mixed results: one trial with six women reported ~15% greater retention of a sperm stimulant after orgasm, but it did not measure actual pregnancy outcomes.
- The evidence remains inconclusive and tabloid headlines overstate implications.
Ultrasound Showed A Fetus Masturbating For 15 Minutes
- A sonogram captured a seven-month fetus repeatedly touching and grasping his penis for about 15 minutes, demonstrating fetal self-stimulation in utero.
- The observation was published as a brief letter with two still ultrasound images and an author's note about the 15-minute observation.
