Blighted Ovum HCG Levels
Blighted ovum is a medical condition in which a fertilized egg implants in the uterus but fails to turn into an embryo. The technical name for the condition is an "anembryonic pregnancy." Blighted ovums account for about half of all miscarriages during the first trimester of pregnancy. Miscarriages are failed pregnancies which terminate themselves without medical intervention. Usually a miscarriage will pass harmlessly on its own—although psychologically a miscarriage can be very traumatic to deal with, if you're aware you're having one. Blighted ovums can occur so early in the course of pregnancy that some women don't even realize they were ever pregnant.
Blighted ovums can elude detection for weeks, however—you may experience signs that you are pregnant, only to find out on your ultrasound later that you're going to have a miscarriage. HCG levels often don't indicate whether you have a blighted ovum at all. Your levels may continue to rise at the normal rate—or may continue to rise, but not at the normal rate (which would be a cause for concern and likely lead to the diagnosis). The reason the HCG levels keep rising with a blighted ovum is that the placenta (which is producing the HCG after implantation) is continuing to grow for a while. It takes your body a bit of time to realize that there is no fetus and that it's time to terminate the pregnancy.
Since you can't look to your HCG levels to necessarily indicate whether you have a blighted ovum, it's best to be alert for signs of a miscarriage. You may experience abdominal cramps or vaginal bleeding or spotting after you test positive for pregnancy. Some women never test positive for pregnancy but simply have what they believe to be a particularly heavy period if the miscarriage occurs very early on.
If you are having abdominal cramps or vaginal bleeding after you test positive for pregnancy, you should talk to your doctor, even if your HCG levels are still rising at the expected rate. While abdominal cramping is normal later in pregnancy, early on it can be a warning sign that something is wrong. Vaginal bleeding is almost always a bad sign. If your HCG levels are rising too slowly, your doctor will want to investigate whether or not you are displaying other miscarriage symptoms.
A blighted ovum won't always be detected until the miscarriage occurs or the ultrasound shows no fetus—sometimes HCG levels rise as usual and there are no other symptoms of miscarriage. Most pregnancies go smoothly however, so do your best not to worry too much about it. If you have no abnormal symptoms, you probably have a completely normal, healthy pregnancy. The good news is that even if you do have a miscarriage, you probably won't have another blighted ovum. This condition usually only occurs once in a lifetime owing to problems with chromosomes in one particular egg or sperm. You will probably have a normal pregnancy if you try again.