Where did you get that last sentence from. By working backwards from your conclusion?
It just kinda jumped out at me one day while I was reading through the gospel account of our Lord's reception in Nazareth -- "Isn't this Mary's son, the carpenter?" Why was Jesus identified by His relationship with Mary, when just about everyone else in the Bible is identified by the name of his father? I'm assuming you don't start a marriage by running off to spend three months with your cousin (Elizabeth). If I'm not assuming too much (hey, I'm not infallible!) -- then the earliest Jesus could have arrived would have been six months after the wedding. There's a folk saying, "The first baby can come at any time. All the rest take nine months." Still, everyone knows how long gestation normally takes.