Not really, the Jurians age really slowly even slower if the are bonded to a tree, The Emperor... Azusa Juri... is prime example as he has been on the thrown for possibly over a thousand years. Sasami is not only bonded to a tree... she is bonded to the Mother-Of-All-Trees Tsunami. Not only that but she is also a Demi-Goddess by merging her soul with that of her peoples goddess... the Elder Choshin Tsunami.
Now baring that in mind we need to remember that she was on board her sisters tree ship for SEVEN-HUNDRED YEARS!!! Meaning that while chronologically she is more than legal, physically she is no older than seven or ten but caries herself with a sense of maturity far in excess of that then even her older sister Ayaka or even that of her mother Misaki. Also this picture has Sasami with the body of a sixteen maybe eighteen year old while still retaining the head of an seven or ten year old little girl.
For this artist to feel comfortable with their work of Sasami being pregnant, her face needs to be aged up a few years into that of a young Tsunami.
Yes she is from Tenchi muyo. I'm not to fund of drawing those girl pregnant but I'm tried of these people sending me messages asking for the others Tenchi girls to be pregnant like I did with the first girl.