She is pregnant with triplets

A couple of weeks pass, and you get another call from Caitlin. She is going to have her first ultrasound, and since you are the biological father, she wants you to join her. You enter the examination room and watch as the nurse starts the machine and inserts the probe into her vagina. "So... get ready for some amazing news", the nurse says. She then points to a pulsating mess of pixels on the screen and says: "This is the heartbeat of your baby". Caitlin looks extremely happy, and sheds a tear. "And here's the second baby... and here's the third... Congratulations, you are having triplets!"

Caitlin exclaims "What!" in an expression of mixed happiness and shock. "You know, I took some fertility drugs after the second failed period... and by 'some' I mean a lot... I exceeded the prescribed dose... guess that made me a bit TOO fertile..."