Some women are reporting that they are diagnosed with a blighted ovum at their first ultrasound, which may be as early as 6 weeks, and are told that they should have a D&C straight away (maybe only a day or two later). It is unusual for a doctor to want to act so quickly so if this is the case for you it may be worth getting a second opinion.
It is only in rare cases that it is necessary to have a D&C straight away and in most cases of a blighted ovum you should wait for a week after the first diagnosis to get a second ultrasound done to confirm it. If the first ultrasound is done early then it may be the case that the embryo cannot be seen at that stage and that needs to be ruled out before going any further.
It is difficult to know just by testing HCG levels if it is a blighted ovum as these may still increase in some cases.
It is quite likely/possible that you will miscarry naturally with a blighted ovum so unless you are further into the pregnancy then it shouldn’t be the case that you have to go straight for a D&C if you want it to happen naturally. Tell your doctor if you want to try and wait for it to happen and they should be able to tell you if this is OK or not. Before the natural miscarriage occurs you may experience some spotting or cramping but it may only be very minor. For some the miscarriage may start with little or no previous indicators.