What neither Jeff or Tricia realized that when Tricia gave Jeff a woman's body that it also had given hims her cycle which she didn't realize that it had been her most fertile time of the month.
For some reason when things settle down Jeff had said he was horny. Tricia then says she was also horny. Jeff then said that this would give them a chance to see what sex is from the other side.
Jeff had made sure the door was locked and then they stripped. Because Tricia usually would take her birth-control pill but she had forgotten to get it refilled. Jeff usually would wear a condom but he had forgot to buy some.
Tricia says that she wanted to have the sex right away and Jeff agreed. What neither realized was that when they did the changes that they had up there libido.
They had sex and fell asleep.
What happens is that because they hadn't used protection that Jeff has gotten pregnant.
Tricia and Jeff decided that wanted to change back but it gives them a error message.