Gillian Anderson is 55! And she looks it. That is not to say she looks bad, not at all. If Jean is supposed to be the same age, she would have given birth to Otis at 38 which is already on the older side. To have a surprise pregnancy and a healthy baby 17 years later is too far fetched. The chance of getting pregnant in your 50s without medical intervention is basically zero.
I agree with Bastet, if they wanted Jean's romance to break up and have her be a mess, they should've come up with a more believable way.