Scrotal temperature is increased in disposable plastic lined nappies 2000; 83:364-8
Leading article: How vulnerable is the developing testis to the external environment? 2000;83:281-2
The use of disposable nappies may explain the increase in male infertility over the past 25 years, suggests a study in the Archives of Disease in Childhood. Nappies lined with plastic significantly increase the temperature of the scrotum - the testicular sac - in boys, the research shows. Temperature is critical to normal testicular development and sperm health.
The research team monitored the scrotal temperature of 48 healthy boys, including five premature babies, from birth up to the age of 42 years, using a tiny thermal probe. The study ranged over two 24-hour periods: during one the boys wore re-usable cotton nappies; during the other, they wore plastic-lined disposable nappies. Temperature was measured during waking and sleeping hours; and rectal temperature was also measured for comparison.
Temperature was consistently and significantly higher - up to 1° C above body temperature - when the disposable nappies were worn. The highest temperatures were recorded in the youngest babies. Rectal temperatures were significantly lower than scrotal temperatures when the children wore disposable nappies, but were the same when cotton nappies were worn. This, says the authors, shows that the insulation properties of the disposable nappies impaired normal testicular cooling mechanisms. In 13 boys, the cooling mechanism failed altogether.
In adults the evidence shows that exposure to high temperatures, for example during episodes of fever or while in a a sauna, can reduce sperm count, and has been used as a form of contraception in men. The subsequent risk of adult infertility in boys whose testicles fail to descend at the normal age is thought to be attributable to increased testicular temperature. A prolonged increase in scrotal temperature in early childhood may therefore have an important role in subsequent testicular health and function, with implications for male fertility, say the authors.
Professor Wolfgang Sippell, Department of Paediatrics, University of Kiel, Germany. firstname.lastname@example.org
Professor Hughes, Department of Paediatrics, University of Cambridge, Cambridge. email@example.com