In her (fertile) womb!

"S-Stay right there!" You moan as you feel your nuts tightening. The Matron shudders as another orgasm hits her, drawing out your own climax. You moan loudly as you fire off several virile ropes of cum into the Matron's womb, her orgasm pulling your seed deep inside her.

"I-I should probably tell you Mr Doe that I'm at my peak fertility right now, even at 52 I can still get pregnant."

The news makes you fire off another rope of cum, making sure that you impregnated the Matron.