3+ ketones in my urine in 37 week pregnancy

Oh dear, I really feel you on this, being a first-time mum at 37 weeks and seeing something like that on your urine test is genuinely scary, and it makes complete sense that you're worried. From what I've heard from other mums, 3+ ketones usually means your body may not be getting enough carbohydrates or fluids, so your body starts breaking down fat for energy instead, it's sometimes called starvation ketosis, and it can happen even if you feel like you've been eating. My neighbour actually had something similar flagged at her 36-week check and her doctor explained that it's important to distinguish between just being dehydrated versus not eating enough, because the treatment approach can be a little different. The most important thing right now is to please don't wait, call your OB or midwife today and let them know the reading, especially since 3+ is on the higher end and at 37 weeks they will want to monitor you and baby properly. Do check with your own doctor rather than rely on what any of us say, as every pregnancy is different and yours deserves proper professional eyes on it.