Many women experience vaginal dryness at some time and may use vaginal lubricants. This is especially true for couples trying to conceive since the stress associated with suspected infertility, or intercourse on demand when using fertility indicators, only makes matters worse. Recent estimates suggest that at least 75% of couples trying to conceive suffer from vaginal dryness. Natural vaginal moisture plays an important role in fertility by providing the right environment for sperm. Vaginal dryness can reduce fertility, lead to painful intercourse, lead to infection, which will further reduce fertility, thus creating a negative spiral. Many women rightly look to vaginal lubricants to deal with the problem but what neither they, nor their doctors often realise is that many vaginal lubricants are hostile to sperm !

The optimum pH value for sperm migration and survival in the cervical mucus is between 7.0 and 8.5 (according to the World Health Organization manual for examination of human semen and sperm-cervical mucus interaction 4th edition 2000). Sperm are very sensitive to low (acidic) pH and, to a lesser extent, elevated (alkaline) pH. Below pH levels of 6.9, sperm die at a rate that increases with lowering pH.

Sperm are also sensitive to both high and low osmolarities (ion concentration in solution) because these can cause them to either shrink or swell beyond their "critical volume limits". A physiologic osmolarity* around 360 mOsm/kg (that of semen) is best for sperm function.