Understanding Pregnancy Risk After Pre-Ejaculate Exposure

Question
Alright, so the situation was, as best as I can recall, essentially as follows. A few nights ago, my girlfriend and I were enjoying one another, and after a while I adjusted my boxers and accidentally touched a wet place where I had earlier secreted a small amount of pre-ejaculate with the tip of my finger. Prior to this, I had ejaculated, so sperm was likely present in the pre-ejaculate. Later, after a few minutes, during which time the liquid on my finger dried, I began to rub her genital area on the outside of her shorts, but soon thereafter I inserted my finger deep into her vagina and stimulated her. My question is simple: What are the odds of her getting pregnant? As a side note, she was on her period at the time, and has, on average, a one month menstrual cycle.

Thanks,
Collin

Answer
Dear Collin,

The odds would be low. First though, the fact that liquid on your finger had dried was not enough. It really should have been washed with soap and water to be sure. The fact that it dried lessens the chances, but sperm cells are microscopic. There could have been 100 of them still wet under a fingernail... The main factor that makes the chance of conception low is that she was in the middle of her period week. Which essentially means that this took place during the least fertile time during her cycle. Since she typically has regular menstrual cycles of approximately 28 days (the norm), she would be expected to be most fertile during cycle days 11-21 (Day 1 being the first day of her period). In a 28 day cycle, the egg is usually released on/about cycle day 14. The egg will survive up to 24 hours waiting to be fertilized. The variable is that sperm cells can survive up to 5 days under ideal conditions once inside and past the cervix - just swimming around waiting for that egg. BUT - presumably, this took place within the first 5 days of the cycle. So, even sperm cells that would wait around as long as 5 days would still not survive long enough to make it to when she'd be expected to ovulate.

I would expect her to continue to have a normal cycle. I hope this has helped you and answered your question. I do apologize for the delay in answering. I wish you well.

Brenda