Hi mama! Yes, ok lang mag-start ng stretchmark cream or Bio-Oil kahit first trimester pa lang, maraming moms actually start early para maiwasan ang marks. A few of us tried Bio-Oil from the start ng pregnancy at walang problema, though some say it's better to wait until second trimester just to be extra safe. The thing is, most mums love Bio-Oil and it's generally considered pregnancy-safe, pero ang evidence na talaga nyang mapipigilan ang stretch marks ay medyo limited lang, pero sa prevention ng dryness and skin elasticity, sobrang tumutulong talaga. Pero since you're in your first trimester pa lang, definitely worth double-checking with your OB or midwife first para peace of mind, basta kung aprubahan nila, pwede mo na i-start anytime!