A positive pregnancy test is an exciting moment, the starting line for a new adventure… But all falls apart quickly when something goes wrong. Sadly, about 20% of pregnancies ends in miscarriage, and about 80% of those miscarriages are in the first trimester.
The most common and underestimated is the blighted ovum. An awful name for anembryonic pregnancy (without an embryo), a type of early pregnancy loss. It is difficult to diagnose and equally stressful for a woman. Even more devastating is when there is a blighted ovum misdiagnosed.
- What is a blighted ovum, and how do you get the best diagnosis possible?
- What are the signs and symptoms?
- What are your treatment options?
Table of Contents
What is a Blighted Ovum?
First of all, I will explain what happens in a normal pregnancy: The future embryo travels to the uterus, after egg fertilization in the Fallopian tubes. Once there, a very important phenomenon occurs: the implantation. This stage is an intimate dialogue between the blastocyst and the uterus.
And, while this dialogue starts, a previous process is already happening within the blastocyst: the cell differentiation. Two main structures will appear at this point: the embryonic sac -which will develop into the placenta- and the embryo itself. Once the embryo implants within the uterus, this differentiation will continue, giving rise to all systems and organs of a human being.
Here is where a very sad -but frequent- phenomenon happens: the blighted ovum. Nowadays, known as anembryonic pregnancy because an empty embryonic sac develops, is a clinical pregnancy that will end in a miscarriage. According to the American Pregnancy Association, half of all first-trimester miscarriages are due to a blighted ovum.
What Are the Symptoms of a Blighted Ovum?
While, most of the time, an anembryonic pregnancy (remember that is the other name for blighted ovum) will end without a woman noticing it. But sometimes, it could develop into an early pregnancy before it stops (before 12 weeks).
As the blighted ovum is a type of pregnancy status, you may still have a positive pregnancy test. And this is because of the growing placenta and the release of the pregnancy hormone: human chorionic gonadotropin (hCG).
As hCG continues rising, you may have symptoms of pregnancy: experience a missed menstrual cycle and breast tenderness. However, at some point, the lack of embryo development triggers the end of the pregnancy. Which could lead to you experiencing abdominal cramps, slight pain, and/or vaginal bleeding.
What Causes a Blighted Ovum?
Well… you have to know that blighted ovum is a type of early pregnancy loss, also called miscarriage or spontaneous abortion. Early pregnancy loss encompasses: complete abortion to a threatened abortion and also includes anembryonic pregnancy.
What causes an early pregnancy? Unfortunately, science does not have the answer (yet), it is estimated that between 50-82% of early pregnancy loss is caused by chromosomal abnormalities in the embryo, and most anembryonic pregnancy are do to this.
The chromosome abnormalities lead to a misunderstanding between the embryo and the uterus during implantation or the embryo’s growth. A retrospective study from 1999 to 2006 analyzed the chromosome abnormalities of 272 first-trimester miscarriages, with or without embryo presence (this is embryonic abortion versus anembryonic pregnancy). They found out that 65% of all miscarriages have chromosome imbalances. Even more, both embryonic and anembryonic pregnancy loss have 58% and 68% chromosome abnormalities, respectively, showing that genetic alterations increase the risk of miscarriage.
Chromosome imbalance happens randomly, but egg or sperm (yes! The sperm is an important player in miscarriage) quality, as well as abnormal cell division after fertilization, increase the risk of early pregnancy loss in general, and blighted ovum in particular.
I don’t want to forget to mention that there are also maternal risk factors. While some of them are not understood, like ethnicity, where Black Women have an increased incidence of early pregnancy loss compared to White Women, some of them are exhaustively studied, such as maternal age, where women up to 45 years old have 53% more chances to suffer early pregnancy loss due to chromosome imbalance. Obesity, metabolic and hormonal disorders, along with lifestyle can all increase the risks as well.
How Common is a Blighted Ovum?
As we previously discussed, a blighted ovum often happens so early in a pregnancy that the woman may never know she was pregnant. Although the exact proportion is unknown, the American Pregnancy Association estimates that 3 of 20 pregnancies ends early, and 50% of them are due to blighted ovum.
Although the statistics seem low, losing a pregnancy can be a difficult process, that may come with a variety of emotions. Take your time to process your emotions and grieve the loss. Talk to your friends and family. A blighted ovum is a random event, but with the right information and support you can work through it.
How is a Blighted Ovum Diagnosed?
A Blighted Ovum could be diagnosed as early as your first medical appointment. To diagnose a blighted ovum your doctor will do a sonogram (or ultrasound scan) to look for a developing embryo around 7-9 weeks.
Doctors have to make a differential diagnosis, so they have to look at the uterus and attempt to visualize the gestational sac to confirm if there is a developing embryo. To achieve this, they will perform a transvaginal ultrasound (an internal examination where the ultrasound wand will be inserted into your vagina) or a transabdominal ultrasound (in this case the ultrasound wand on your abdomen). If the gestational sac is empty, the diagnosis is a blighted ovum.
Sometimes, especially in women with irregular periods, the doctor must follow up with a new scan in about 11-14 days to ensure no embryo is growing.
Remember: another possibility is you may have some light bleeding between the positive pregnancy test and the scan. If implantation never happens the doctor does not find the gestational sac on the scan. This is diagnosed as an early pregnancy loss or biochemical (or chemical) pregnancy.
How is a Blighted Ovum Misdiagnosed?
As with every medical issue, a blighted ovum misdiagnosed could happen. None of us hope or often expect that it will happens to us, but none of us are exempt.
To understand how a misdiagnosis could occur you must first know some facts about embryo development: after fertilization, the blastocyst implants within the uterus about one week later. In this scenario, the future embryo will grow and become visible for the scan around the 5th or 8th week of gestation, depending on if it is a transvaginal or abdominal ultrasound, respectively.
There are cases when an abdominal scan performed too soon could lead to a misdiagnosis of a blighted ovum. This could happen when the ultrasound is run before the 8th week of gestation or when the date of conception is uncertain and the embryo is unable to be seen with an abdominal ultrasound.
Other times, the woman feels pregnant because the hCG levels are high and the pregnancy symptoms remain, although the embryo has already been absorbed. In this case, a blighted ovum could be misdiagnosed as an early pregnancy loss.
How to Avoid a Misdiagnosis?
A positive pregnancy test is an emotional moment -with happiness, fear, and a lot of questions- so take a deep breath and pay attention to your body.
Here are some tips for you, no matter if you have pregnancy symptoms or not:
If you have an early negative or doubt the scan, repeat it 2-3 weeks later. Your doctor can again check to see if the embryo is growing, and you could listen to its heart beat!
If you start feeling pain or have light blood stains, check with your doctor about the possibility of infections. In this case, you may need an early scan to check your uterus.
If you have any doubts about anything, get a second opinion, and find another professional. Also try to avoid reading too much on the internet. Sometimes anxiety plays a huge role, and you may start to see and read some misinformation.
We are all different, and not everyone presents in the same way! Some women have intense pregnancy symptoms -like morning sickness every day. But others do not or have only slight signs, like breast tenderness. A positive pregnancy test only checks for hCG levels, not implantation or embryo development, so if you have doubts, check with your medical care provider!
What Choices Do I Have for Treatment?
As discussed in our previous article about PCOS and ectopic pregnancy, there are 3 different treatment options when it comes to a non viable pregnancy: expectant, medical, and surgical treatment. Which one is better for you will depend on an (informed) conversation between you and your medical provider.
The medical management of ending pregnancy has become more suitable and safer (for the mother) than surgical management. When we talk about blighted ovum, the most common drug administered is misoprostol instead of methotrexate (which effectively ended ectopic pregnancy). This drug increases uterine contraction, leading to abortion. However, despite a more predictable treatment, the optimal dose is still under research.
Surgical management, usually called D&C (dilatation and curettage), is used in women with hemodynamic instability, while expectant management -to wait for the miscarriage naturally happens- is an option that must be followed up closely by your clinician because significant bleeding could be signs of infections and can be unsafe.
Frequently Asked Questions
Can a Diagnosis of Blighted Ovum Be Wrong?
Not Really. But a misdiagnosis of a blighted ovum would happen if the scan is performed sooner than the 8th week gestation. In that case, you should repeat the scan in 2 weeks.
Is a Blighted Ovum My Fault?
Of course not! It is a random event that you can do nothing about.
Can hCG be Normal with a Blighted Ovum?
Yes! And this is because the growing of the gestational sac (the future placenta), not the embryo.
At What Stage Do Blighted Ovums Typically Miscarry?
Miscarriage should naturally happen between the 7th and 11th week of gestation. However, most of the time it happens before you know that you are pregnant.
The path of discovering a misdiagnosed blighted ovum is undeniably challenging, especially when you’ve been eagerly anticipating a pregnancy.
Pregnancy tests have evolved to detect even the faintest traces of hCG, offering hope from the beginning. However, when your doctor hesitates over the sonogram results, the weight of uncertainty can feel overwhelmingly stressful.
Several weeks later, the dreaded news finally arrives. Despite often hearing that miscarriages are common when it happens to you, it becomes heartbreaking. In that moment it is meaningful to remember that your feelings are valid. Talking about your emotions, sharing your pain, and seeking professional support can help you to heal.
Despite the awful name, it’s essential to acknowledge that the causes behind a blighted ovum remain elusive, random as they are. And yet, once your doctor gives you the green light, you can return to your journey to trying again.
Monica has a Ph.D. specializing in molecular and cell biology. with more than 10 years in reproductive medicine, she has now turned to medical and scientific communication through writing. She is passionate about scientific writing, and her goal is to turn the complex language of science into simple and relatable words.