Delay sprays can affect your chances of conceiving, but they pose minimal risk to an existing pregnancy. The active ingredient in most delay sprays is lidocaine (typically at 5%) or benzocaine, both of which are mild numbing agents. Their impact depends on whether you’re trying to get pregnant or are already pregnant.
How Delay Sprays Affect Sperm
Lidocaine is toxic to sperm on direct contact. A lab study on Promescent, one of the most popular lidocaine-based delay sprays, found that it caused a statistically significant drop in sperm motility (the ability of sperm to swim), forward progression, and overall viability compared to untreated samples. In plain terms, sperm exposed to the spray moved less, moved more slowly, and died at higher rates.
This matters because delay sprays are applied to the penis and can transfer to the vaginal canal during intercourse. Even small amounts of residual lidocaine reaching the cervix could impair the sperm’s journey. The study did not find an increase in sperm DNA damage, so the concern is less about harming the genetic material and more about whether enough healthy, mobile sperm survive to reach the egg.
Does It Reduce Your Chances of Conceiving?
If you’re actively trying to get pregnant, delay spray adds an unnecessary obstacle. The sperm-killing effect observed in the lab is real, though it’s worth noting that lab conditions (where sperm sit in direct contact with lidocaine) are more extreme than what happens during sex, where the spray is partially absorbed before intercourse and diluted by natural lubrication.
For context, a large prospective study of couples trying to conceive found that common lubricants, which also reduce sperm motility in lab settings, did not actually lower pregnancy rates in real-world use. Fecundability (the probability of conceiving in a given cycle) was essentially the same whether couples used water-based, oil-based, or silicone-based lubricants compared to no lubricant at all. However, delay sprays contain an active pharmaceutical ingredient designed to numb tissue, which is a different situation from a simple lubricant. No equivalent real-world fertility study has been done specifically on delay sprays.
The practical advice: if you’re trying to conceive, skip the delay spray. There’s no reason to introduce a compound known to harm sperm when you’re working toward pregnancy. If premature ejaculation is making conception difficult, that’s a conversation worth having with a doctor, since there are other approaches that won’t involve coating sperm in a numbing agent.
Safety During an Existing Pregnancy
If you’re already pregnant and your partner uses a delay spray during sex, the risk profile looks quite different. Here the question isn’t about sperm survival. It’s about whether lidocaine absorbed through vaginal tissue could reach the developing baby.
Lidocaine was classified as Pregnancy Category B by the FDA, meaning animal studies showed no evidence of harm to the fetus, but there are no large, well-controlled human trials. A study of 293 women exposed to lidocaine during the first four months of pregnancy found no higher rate of birth defects. Animal reproduction studies using doses many times higher than what humans typically encounter also revealed no teratogenic (birth defect-causing), embryotoxic, or fetotoxic effects.
The amount of lidocaine in a delay spray is small, typically a few milligrams per application, and only a fraction of that would transfer to a partner’s vaginal tissue during intercourse. A study that measured lidocaine levels in cord blood after direct vaginal application of lidocaine spray during labor found that 86 out of 88 samples contained low or very low levels. The two samples with higher readings were likely caused by direct contact with the baby’s scalp during delivery rather than placental transfer.
In short, the trace amount of lidocaine that might reach the bloodstream through brief sexual contact is far below any level associated with fetal risk.
What About the Partner’s Experience?
One practical concern that often gets overlooked: lidocaine transferred during sex can numb vaginal tissue, reducing sensation for the pregnant partner. This isn’t a safety issue, but it can be uncomfortable or surprising. Most delay spray instructions recommend waiting 10 to 20 minutes after application before sex and wiping off excess product, which reduces transfer. Using a condom eliminates transfer almost entirely, though that obviously isn’t an option if you’re trying to conceive.
The Bottom Line for Each Situation
- Trying to get pregnant: Avoid delay spray. Lidocaine kills sperm on contact and reduces their ability to swim. No real-world conception study has tested delay sprays specifically, but the lab evidence is clear enough to warrant caution.
- Already pregnant: The risk is very low. Lidocaine has not been linked to birth defects in human or animal studies, and the tiny amount that could transfer during sex is far below any concerning threshold. The main side effect is reduced sensation for the pregnant partner.
- Not trying to conceive, partner is pregnant: There is no meaningful safety concern for the pregnancy. Standard application instructions (wait before sex, wipe excess) minimize any transfer.