Megillah 13b - Contraception with Who?

Tosafos solves the problem of havchana between mordechai and achashveirosh by saying that esther was mishameshes b'moch. The maharsha says that with mordechai it would have been assur to be mishameshes b'moch so it must have been with achashveirosh that she used a moch. The obvious question is, so how did she get pregnant with daryavesh from achashveirosh (as rashi writes in r"h)? The maharsha says that after she went to achashveirosh b'ratzon, "ka'asher avadti, avadti", she stopped using a moch with achashveirosh since there was no longer a concern of havchana.

The Turei Even says that she got pregnant from achashveirosh bec. she used a moch with mordechai. The kunteros acharon (on turei even) says that the Turei Even must be correct, not the maharsha. He explains that esther became assur to mordechai in the 12th year of achashveirosh being king (that was when haman drew the lots), and achashveirosh was only king for 14 years, which was immediately followed by daryavesh taking over and granting permission to build the beis hamikdash. If the maharsha is correct that she only became pregnant with daryavesh after she was already assur to mordechai, then daryavesh would only be 2 and a half years old when he gives permission to build the beis hamikdash - which is highly unlikely!