Eh normal je sayang, hiccups tu memang part of pregnancy kan, at 31 weeks baby's nervous system dah developed enough untuk buat reflex-reflex macam tu. A few of my mum friends ngan 7-8 months pregnancies pun cakap sama, pastu hilang je on its own, nothing to worry about. But if you're uneasy or rasa ada yang lain, better check with your OB next appointment just to be on the safe side, okay?