Yes, hCG levels do rise with a blighted ovum, which is why you’ll get a positive pregnancy test and may even experience typical early pregnancy symptoms like nausea and breast tenderness. However, hCG levels in a blighted ovum are significantly lower than in a healthy pregnancy and often rise more slowly or plateau earlier than expected.
Why hCG Still Rises Without an Embryo
hCG is not produced by the embryo itself. It’s produced by the trophoblast, the outer layer of cells that forms after a fertilized egg implants in the uterine wall. These cells are the early beginnings of what would become the placenta. In a blighted ovum (also called an anembryonic pregnancy), a gestational sac forms and implants normally, and the trophoblast tissue briefly begins developing. That tissue releases hCG into your bloodstream just as it would in a viable pregnancy.
This is why a home pregnancy test can’t distinguish between a healthy pregnancy and a blighted ovum. The test only detects the presence of hCG, not its source or rate of increase. Your body responds to that hCG the same way it would in any pregnancy: it stimulates the corpus luteum in the ovary to produce estrogen and progesterone, which maintain the uterine lining and trigger symptoms like morning sickness, fatigue, and sore breasts. Research on anembryonic pregnancies confirms that hCG acts as the primary driver of these hormones when no embryo is present.
How hCG Levels Differ From a Healthy Pregnancy
While hCG does rise in a blighted ovum, the pattern looks different. A study in Human Reproduction that compared 22 anembryonic pregnancies to 52 normal pregnancies found that hCG levels were significantly lower across the board in anembryonic pregnancies between weeks 4 and 11. The same was true for estrogen and progesterone levels.
In a typical healthy pregnancy, hCG roughly doubles every 48 to 72 hours during the first weeks. With a blighted ovum, hCG may rise more slowly, plateau at a lower peak, or begin declining earlier. This is why doctors sometimes order serial hCG blood draws two to three days apart. A single hCG number can’t confirm or rule out a blighted ovum, but the trend over multiple draws can raise a red flag. Levels that fail to double appropriately or that stall suggest the pregnancy isn’t developing normally.
That said, hCG patterns vary widely from person to person, even in healthy pregnancies. Slow-rising hCG is a warning sign, not a diagnosis on its own.
How a Blighted Ovum Is Actually Diagnosed
The definitive diagnosis comes from ultrasound, not hCG levels. Current diagnostic guidelines consider a blighted ovum confirmed when a transvaginal ultrasound shows a gestational sac with a mean diameter of 25 millimeters or greater and no visible embryo inside. At that sac size, an embryo should be clearly visible if the pregnancy were viable.
This measurement matters because diagnosing too early is a real risk. A smaller sac might simply mean the pregnancy is earlier than estimated, and an embryo could appear on a follow-up scan. Doctors will often schedule a repeat ultrasound one to two weeks later if the initial findings are uncertain, particularly if the sac is smaller than 25 mm. The goal is to avoid misdiagnosis of a pregnancy that’s simply earlier than expected.
What Happens After Diagnosis
Once a blighted ovum is confirmed, the pregnancy will not become viable. There are three main paths forward: waiting for your body to pass the tissue on its own, medication to help the process along, or a minor surgical procedure.
Expectant management, meaning waiting without intervention, results in complete passage of pregnancy tissue about 52% of the time within the first two weeks and roughly 66% within six weeks. These rates are lower than for other types of early miscarriage, where the success rate for natural passage can be above 90%. If the tissue doesn’t pass on its own within a reasonable timeframe, medication or a procedure becomes the next step.
After the pregnancy tissue has passed or been removed, hCG levels gradually decline back toward zero. Your doctor may monitor hCG with periodic blood draws to confirm the levels are dropping appropriately. Most people see their levels return to non-pregnant range within a few weeks, though the exact timeline depends on how high hCG climbed before the pregnancy stopped progressing.
Pregnancy Chances After a Blighted Ovum
A blighted ovum is the most common cause of early miscarriage, and most are caused by random chromosomal abnormalities in the fertilized egg, not by an underlying health problem. Having one doesn’t mean you’re likely to have another.
After a single miscarriage of any type, the risk of miscarriage in the next pregnancy is about 24%. After two consecutive losses, that rises to about 30%, and after three or more, to roughly 35%. For comparison, women with no prior miscarriages or a previously successful pregnancy have a baseline miscarriage risk of 5 to 10%. The important takeaway is that even among women with recurrent pregnancy loss, most eventually have a successful pregnancy without any specific treatment.