A woman at her first pregnancy should seek help from a qualified gynecologist.
IMHO, that sentence is awkardly constructed.
I would phrase it thusly: "When pregnant for the first time, a woman should seek the medical expertise of a qualified gynecologist."
Another possibility could be: "At the first SIGNS of pregnancy, a woman should seek the medical expertise of a qualified gynecologist."
I'm aware that the second sentence has a different meaning due to my belief that a woman should consult a gynecologist during any pregnancy ... not just the first
one. However, this could be a debatable issue as the prenatal medical practices in North America may differ from where you live.