The effect of a copper-releasing intrauterine device on sperm penetration in human cervical mucus in vitro.

Improvements in the acceptability and effectiveness of the IUD involve developments in design of its shape such as the Dalkon Shield (Davis, 1971), or the addition ofa copper-releasing wire to the inert plastic material of the device, which was first reported by Zipper, Medel & Prager (1968). The copper could act at any stage in the reproductive process. It could interfere with sperm transport, destroy the fertilized egg or blastocyst, disturb the intrauterine environment preventing implantation, or might owe its effectiveness to a combination of actions. In rats, the presence of copper in one uterine horn does not affect implantation in the other horn (Chang & Tatum, 1970), indicating that the effect is local. It was also observed in rats that a copper implant in the uterus did not interfere with fertilization but prevented implantation. It has been suggested that this prevention of implantation may be due to the specific attraction of leucocytes into the uterine lumen (Cuadros & Hirsch, 1972). It is not possible, however, to extrapolate completely from animal experiments to man as repro¬ ductive mechanisms vary considerably. We decided to study the effect of the copper released from these IUDs on the transport of spermatozoa through cervical mucus, the physical properties of which vary throughout the menstrual cycle. Sperm penetration is maximal at mid-cycle when the mucus is of low viscosity and free of cells and exhibits the rheological property of spinnbarkeit. Cervical mucus was obtained from normal women at mid-cycle and incubated with a copper-coated stem of the Gravigard IUD (Searle) in a humidity chamber at 37° C for 20 hr. Another portion of each mucus sample was incu¬ bated for the same length of time without a copper IUD. The average volume'of each sample incubated was 0-2 ml. After 20 hr, the spinnbarkeit of each sample was tested (Clift, 1945), and a capillary sperm penetration test was performed (Kremer, 1965), using normal motile spermatozoa from the same specimen of semen which was used for each pair of mucus samples. The linear penetration of the spermatozoa was recorded in millimetres, and theirmotility was assessed. A portion of the mucus was also assayed for copper, using spectrophotometry and oxalydihydrazide based on a method described by Rice (1960). After incubation with the copper, there was a loss of spinnbarkeit. The mucus became watery and could not be drawn out into threads, confirming the findings