I met a beautiful youngish woman at work which prompted this fantasy.. She tells me that she is trying to fall pregnant but it isn't happening. One thing leads to another and she asks me to impregnate her. I meet with her and her husband and explain that this is a service I am offering. He mustn't worry that I am trying to take his place or be romantic, I'm just basically delivering the needed sperm. I go on to explain that conception occurs most effectively when the woman orgasms as ejaculation happens, that her cervix convulses and basically sucks in the cum. And therefore that I will have to arouse her. We undress and I play caress her abdomen, telling her how sexy it will be when it starts swelling. I play with her breasts explaining how much more beautiful they will be when they start getting bigger, ripe with the juiciness of life. I go down on her, starting slowly with the outside, moving in inwards until I am moving back and forth from her opening to her clit, increasing the pressure as she gets wetter and wetter and opens up, hungry for what is to cum. I then invite her to stroke and lick my hard cock, become familiar with what will impregnate her. Explain how my length will deliver the juice right up against her cervix, how the width will make sure she is open up to the maximum. I invite her to feel and gently suck on my balls, heavy with their potent seed. I slip into her wet opening and start thrusting with increasing pace and passion. I feel the time is coming, observe as she builds up to her biggest orgasm. I ensure her husband is behind me so that he can see my balls contract in preparation. So that he can see my shaft convulse as I fill his fertile wife's belly. As I feel her going over the edge I let go. I can feel my semen shooting through my cock, feel it leave the opening and splashing against her cervix, I am buried to the hilt and waves wash through me is I flood her insides with my hot cum.