Q. We have read several articles saying that certain contents in lubricants are bad for sperm for people trying to conceive. These contents are found in the lubricant we are currently using.

The lubricant states that 'it is not a contraceptive and does not contain spermicide'. We are confused. We would like to know if lubricants in the market deter us from conceiving and, if so, what lubricants would be practical for us?

A. Many couples actively seeking to conceive a child do report vaginal dryness affecting their sexual function and a fear of failure to conceive.

In addition, some fertility medications may reduce the cervical mucus produced around ovulation.

Most of the currently available vaginal lubricants - even small concentrations - seem to dramatically reduce sperm motility (the ability of sperm to move and swim).

In addition, a number of studies have shown that some vaginal lubricants can affect sperm viability (percentage of live sperm) as the lubricants can cause sperm to shrink or swell beyond their 'critical volume', thus killing the sperm.

Sperm is very sensitive to low pH - the measure of the acidity or alkalinity of a solution - and may also be 'immobilised' by vaginal lubricants which have pH below 7. (The scale ranges from 0 to 14.)

Thus, most vaginal lubricants are not good for fertility even though they do not contain contraceptives nor do they contain spermicides which specifically destroy sperm.

A 1984 study from Canada showed that human saliva had a harmful effect on sperm survival and activity and it is not advised as a lubricant for couples intending to conceive.

A new vaginal lubricant available on the market, Pre-seed, is said to be sperm friendly - it has a pH of 7.3 and does not significantly reduce sperm motility and survival.

This is currently available in Singapore at Raffles Hospital (Women's Centre), KK Women's and Children's Hospital and through private gynaecologists.

Dr Sheila Loh

This article was first published in Mind Your Body, The Straits Times on July 16, 2008.