Obviously, when trying to get pregnant, you wouldn't want to use a lubricant that contains spermicide. However, even lubricants like Astroglide and KY Kelly without spermicide can inhibit and kill sperm.
There have been quite a few studies that looked at the effect of various lubricants on sperm. The studies looked at how well the sperm swim (motility), whether or not DNA damage occurred, and whether sperm were still alive.
Popular lubricants like KY Jelly, Astroglide, and Replens were found to inhibit sperm movement and even kill sperm. Every study I looked at cautioned against the use of common lubricants for couples trying to conceive.
Note that while regular lubricants aren't great for trying to get pregnant, they cannot be expected to act like birth control. They make it less likely for pregnancy, but they don't prevent it.
Sperm Friendly Lubricants
There are lubricants that have been made to be fertility friendly. The most popular sperm friendly lubricant is PreSeed. Others include ConceivEase, Yes Baby, Conceive Plus, and Zestica.
It may be possible to use raw egg whites as a personal lubricant, but there is a risk of allergic reaction (if you have an allergy to eggs) and possible salmonella poisoning. Plus, it's kind of messy.
Canola oil and plain baby oil are possible options, but they may lead to vaginal infection or irritation.
In case you're wondering, saliva is not a sperm friendly option. The acidity is harmful to sperm.
The Bottom Line on Lubricants When Trying to Get Pregnant
Unless a lubricant has been specifically made for trying to conceive, you should be wary. Both water- and oil-based lubricants have been found to interfere with sperm movement, and some kill or alter the DNA of sperm.
It's also important to mention that a lack of arousal fluids or cervical mucus may indicate a fertility problem. If this is a common problem for you, and you have not mentioned it to your doctor, be sure to speak up. It may help your doctor treat your infertility.
Agarwal A, Deepinder F, Cocuzza M, Short RA, Evenson DP. "Effect of vaginal lubricants on sperm motility and chromatin integrity: a prospective comparative study." Fertility and Sterility. 2008 Feb;89(2):375-9. Epub 2007 May 16.
Anderson L, Lewis SE, McClure N. "The effects of coital lubricants on sperm motility in vitro." Human Reproduction. 1998 Dec;13(12):3351-6.
Kutteh WH, Chao CH, Ritter JO, Byrd W. "Vaginal lubricants for the infertile couple: effect on sperm activity." International Journal of Fertility and Menopausal Studies. 1996 Jul-Aug;41(4):400-4.