Sis, usually ang OB mo na ang mag-check ng cervix, especially closer to your due date, maybe during your regular checkups na or if you start feeling contractions na, pero better to ask your doctor directly kung gusto mo na talaga malaman ngayon since you're almost 39 weeks na. I have a friend din na first-time mom at 36 like you, and honestly ang best approach is just to let your OB guide you based on what they see sa ultrasound at physical exam, kasi every pregnancy talaga is different. Regarding your cleft palate, definitely mention this sa OB mo if you haven't already, they might want to monitor extra or adjust your delivery plan, pero marami talaga kaming kakilala na successful normal delivery with various health conditions, so it's very possible! The key is open communication with your doctor about your concerns so they can help you prepare properly.