My fiance is from Mexico and her stutter is a lot more noticeable when she speaks her native Spanish but when speaks English - you don't really notice it unless she's tired or frustrated. But I think it's a bilingual thing - I don't stutter but I'm from Polish and when I speak in my native language I speak a lot faster and kinda unfiltered but when I speak in English my speech is lot more collected and smoother. I'm not an expert but I believe it's a brain thing.