Uy, I haven't personally experienced that with Utrogestan, but a few of us sa mama group namin have had spotting or light bleeding in early pregnancy, though it's hard to say kung from the meds talaga or just normal pregnancy stuff kasi marami pang iba pang reasons. Since you're 16 weeks na and concerned about this, I'd really suggest checking with your OB agad, especially since you're on medication, mas makakatulong sila ma-assess kung normal lang yan or something to watch. Hoping it's nothing serious, pero better safe talaga! Let us know how it goes, okay?