What is Anembryonic Pregnancy?

An anembryonic pregnancy happens when a sac forms in the womb but no embryo develops. This term and ‘blighted ovum’ mean the same thing, but ‘anembryonic pregnancy’ is now more commonly used because it describes the situation better. It’s thought that this type of pregnancy is responsible for a large, but unmeasured, number of miscarriages. The American Pregnancy Association estimates that anembryonic pregnancies may be behind half of all miscarriages in the first three months of pregnancy. Miscarriages are fairly common, happening in approximately 15% of all pregnancies that we know of. Moreover, only 30% of all pregnancies result in live births.

Many women don’t realize they’ve had a miscarriage, especially when it’s early in the pregnancy. This includes women who’ve had an anembryonic pregnancy.

The terms ‘early pregnancy loss’, ‘miscarriage’, or ‘spontaneous abortion’ are often used to describe the same thing. Early pregnancy loss is when a pregnancy ends naturally before the 13th week.

The World Health Organization (WHO) and the Centers for Disease Control and Prevention (CDC) define a miscarriage as the loss of a pregnancy before the 20th week. They also define it as removal or ejection of an embryo or fetus that weighs 500 grams or less. However, different states in the US may have different definitions.

A ‘biochemical miscarriage’ is a type of miscarriage that happens after a pregnancy test has come back positive, before the pregnancy can be confirmed with an ultrasound scan or tissue examination.

A ‘clinical miscarriage’ is diagnosed with an ultrasound or tissue examination confirming a pregnancy had started in the womb. It’s divided into ‘early’, which is a loss before the end of the 12th week of pregnancy, and ‘late’, which is a loss between the 12th and 20th weeks of pregnancy.

What Causes Anembryonic Pregnancy?

Understanding the exact cause of anembryonic pregnancies, or pregnancies where an embryo doesn’t develop, is challenging. The root causes are often investigated in a wider context, which includes losses of pregnancies in early stages, both when there is an embryo and when there isn’t. Multiple factors can contribute to these losses:

1. Problems with the shape or structure of an embryo can make it hard for the embryo to attach itself inside the womb or survive for a long time after it has attached. These problems are usually tied to issues with the embryo’s chromosomes.

2. Defects in the embryo’s chromosomes are a common cause for early pregnancies losses. These can include extra chromosomes (trisomy), having more than two complete sets of chromosomes (polyploidy), extra sex chromosomes (polysomy), and missing an X chromosome (monosomy X). In fact, trisomies alone account for 30% of all miscarriages and 60% of miscarriages that happen again and again. Trisomy 16, infamous for always leading to a pregnancy with an empty sac, is responsible for 15-25% of all trisomies.

3. Other genetic problems like relocating or flipping chromosome segments, changes in a single gene, and inconsistencies in the chromosomes of the placenta can also contribute. Miscarriages can also occur in pregnancies between close relatives, indicating that a single gene could be the cause.

4. Link between DNA damage in sperm and miscarriage is probable.

5. Being obese or older at the time of pregnancy are known risks.

6. Infections, including tuberculosis and infections of the reproductive tract, are also suspected to contribute. Complications from infections can also make it hard for an embryo to attach itself and grow.

7. malformations of the uterus like having two uterine bodies (didelphic), a two-corned uterus (bicornuate), or a wall dividing the uterus (septate), can stop an embryo from attaching itself and growing long-term.

8. Problems with the mom’s immune system, like dysfunction of a type of white blood cell known as ‘Natural Killer’ cells, development of powerful proteins against body’s own cells (autoantibodies), hereditary and acquired conditions increasing the risk of clot formation (thrombophilia), etc., can result in the womb rejecting the attached embryo, leading to a miscarriage.

9. Hormonal issues, like low progesterone levels, issues with the thyroid, and a condition known as polycystic ovarian syndrome (PCOS), linked with difficulties in getting pregnant and losing a pregnancy, also play a role.

10. Consuming alcohol increases the risk of miscarriage.

Risk Factors and Frequency for Anembryonic Pregnancy

Anembryonic pregnancy, sometimes known as a ‘blighted ovum’, might account for up to half of all miscarriages that occur in the first three months of pregnancy. Roughly 15% of pregnancies that are known about, result in a miscarriage before the 12th week. This risk significantly changes with age – in women between the ages of 20 to 24, 10% experience an early pregnancy loss, but for women between 40 to 44 years old, this increases to 51%. Additionally, having a previous early pregnancy loss also increases a woman’s risk of having a miscarriage.

  • Anembryonic pregnancy potentially makes up half of all miscarriages in the first three months.
  • Approximately 15% of known pregnancies end in a miscarriage before the 12th week.
  • The risk of early pregnancy loss changes with age, from 10% in 20 to 24 year olds, to 51% in 40 to 44 year olds.
  • Having a previous early pregnancy loss increases the risk of another miscarriage.

Signs and Symptoms of Anembryonic Pregnancy

An anembryonic pregnancy, also known as a ‘blighted ovum’, often shows similar signs and symptoms to an ectopic pregnancy. It’s usually noticed by chance during the first routine ultrasound scan in the early stages of pregnancy. Often, people with an anembryonic pregnancy may not notice any symptoms. If there’s an early pregnancy loss, which is a miscarriage, one might experience stomach cramps and vaginal bleeding. However, a miscarriage, in this case, can also happen without any noticeable symptoms.

Testing for Anembryonic Pregnancy

The diagnosis of a condition known as an anembryonic pregnancy is typically confirmed through a combination of careful observation of symptoms, a pregnancy test, and an ultrasound examination. An anembryonic pregnancy, sometimes also called a “blighted ovum,” happens when a fertilized egg implants in the uterus, but an embryo does not develop.

A pregnancy test checks for the presence of a hormone called human chorionic gonadotropin (hCG). This hormone is produced by the placenta shortly after the fertilized egg attaches to the uterine lining. The test can be performed using either a urine sample or a blood sample.

An ultrasound exam is another tool used for diagnosis. It can be performed either across the abdomen (transabdominal) or inside the vagina (transvaginal). In an anembryonic pregnancy, the ultrasound typically shows what’s called an “empty” gestational sac – that’s the sac where the embryo usually develops, but in this case, it doesn’t contain an embryo.

Specifically, a diagnosis of an anembryonic pregnancy can be made if an ultrasound shows no identifiable embryo in a gestational sac that’s 25 millimeters or larger in diameter. Another way to confirm an anembryonic pregnancy is if no embryo is seen in an ultrasound done more than 11 days after an earlier scan showed a gestational sac with a yolk sac (the structure that provides nutrients to the embryo) but no embryo, or if no embryo is seen more than two weeks after a scan showed a gestational sac without any embryo or yolk sac.

Treatment Options for Anembryonic Pregnancy

Early pregnancy loss can be difficult to navigate, and there are several treatment options to consider. These options include:

* Expectant Management: This is often described as a “watchful waiting” approach. Under this method, the patient is closely monitored but without any medical intervention. Instead, it allows for the pregnancy tissue to pass out of the body naturally. During this time, follow-up ultrasound scans and hormone level checks might be performed to confirm that all the tissue has passed. A test indicating low levels of the pregnancy hormone hCG, performed after the passage of tissue, is recommended.

* Medical Management: This approach involves the use of medications like mifepristone and/or misoprostol. These drugs might be administered in different ways such as orally, via the vagina, or placed inside the cheek, and the dose and timing can vary. The optimum dosage is still being researched. This treatment method allows for a more predictable course of the treatment.

* Surgical Treatment: The third option is a surgical procedure which involves uterine evacuation with a manual vacuum or dilation and curettage. This method is often used in cases where a patient cannot handle the cramping and bleeding associated with medical management or if their health is unstable. The procedure is quicker to complete, especially when performed on an outpatient basis.

Ultimately, the choice of treatment is collaborated between the patient and the physician, after a detailed discussion regarding the pros and cons of each method.

When a doctor is trying to rule out an anembryonic pregnancy – also known as a blighted ovum – they might consider other similar conditions. These include:

  • Pseudogestational sac: This condition involves a small amount of fluid in the womb, but no pregnancy tissue.
  • Early intrauterine pregnancy: This is a pregnancy that is still in its very early stages.
  • An ectopic pregnancy: This is a scenario where the pregnancy happens outside of the womb, often in the fallopian tubes.
  • Implantation bleeding: This is normal spotting that can occur from a healthy pregnancy.
  • Gestational trophoblastic disease: This is a rare condition that involves the abnormal growth of cells inside a woman’s uterus.
  • Complications relating to a viable pregnancy: There could be other complications related to a normal and healthy pregnancy.

Each of these conditions presents differently, so it is important for the doctor to carefully assess all possibilities.

What to expect with Anembryonic Pregnancy

The outlook and effective treatment of an anembryonic pregnancy, which is a pregnancy where the egg attaches itself to the uterine wall but the embryo does not develop, varies based on several factors, including how far the pregnancy has progressed. Generally, all three treatment options are considered effective.

One option is expectant management, which means taking a “wait-and-see” approach. A review of 20 studies found that this approach, along with medical treatment, are both suitable treatment options for incomplete abortions, which is where parts of the pregnancy tissue remain in the body after a miscarriage.

Another option is medical management, where medication is used to promote the completion of the abortion. This approach tends to be more successful when multiple doses of a drug called misoprostol are used. This medical treatment tends to be more successful than expectant management for treating incomplete abortions.

The last option is surgical treatment. There’s been at least one major study that found a higher success rate with surgical treatment compared to medical treatment although it concluded that both options are generally safe.

Possible Complications When Diagnosed with Anembryonic Pregnancy

While serious complications from treatment are not typical, they can occur. These can include:

  • Heavy bleeding
  • Damaging the uterus during surgery
  • Infection or a septic abortion (an abortion complicated by infection) which can be life threatening
  • Complications from not diagnosing an ectopic pregnancy (when a pregnancy develops outside the uterus) correctly

Preventing Anembryonic Pregnancy

If you are pregnant and in your first three months (or first trimester), it’s important to immediately go to the emergency room if you experience intense pain or heavy vaginal bleeding. Heavy bleeding is defined as soaking two sanitary pads per hour for two consecutive hours.

It’s also important to be alert for any signs and symptoms of an infection, particularly after having surgery or if you’ve decided to wait and see if the situation improves on its own (this is called expectant management).

Taking the medications mifepristone and misoprostol may cause a fever-like reaction. This might be mistaken for an infection, so it’s vital to be aware of this.

Precautionary antibiotics, medications to prevent infection, typically aren’t given unless you’ve just had surgery.

Follow-up checks including ultrasound scans and outpatient appointments are critical, especially if additional doses of the medication misoprostol are needed for treatment. It’s essential to keep these appointments to ensure your health is on track.

Experiencing a miscarriage can be deeply distressing. It’s crucial to understand that feelings of grief are normal and your doctor will provide much-needed reassurance and compassion during this process.

Frequently asked questions

An anembryonic pregnancy is when a sac forms in the womb but no embryo develops. It is also known as a blighted ovum.

Anembryonic pregnancy potentially makes up half of all miscarriages in the first three months.

Signs and symptoms of an anembryonic pregnancy, also known as a 'blighted ovum', may include: - Similar signs and symptoms to an ectopic pregnancy - Often noticed by chance during the first routine ultrasound scan in the early stages of pregnancy - Some people may not notice any symptoms - Stomach cramps - Vaginal bleeding - However, a miscarriage can also happen without any noticeable symptoms in some cases.

Understanding the exact cause of anembryonic pregnancies, or pregnancies where an embryo doesn't develop, is challenging. The root causes are often investigated in a wider context, which includes losses of pregnancies in early stages, both when there is an embryo and when there isn't. Multiple factors can contribute to these losses.

The other conditions that a doctor needs to rule out when diagnosing Anembryonic Pregnancy are: 1. Pseudogestational sac: This condition involves a small amount of fluid in the womb, but no pregnancy tissue. 2. Early intrauterine pregnancy: This is a pregnancy that is still in its very early stages. 3. An ectopic pregnancy: This is a scenario where the pregnancy happens outside of the womb, often in the fallopian tubes. 4. Implantation bleeding: This is normal spotting that can occur from a healthy pregnancy. 5. Gestational trophoblastic disease: This is a rare condition that involves the abnormal growth of cells inside a woman's uterus. 6. Complications relating to a viable pregnancy: There could be other complications related to a normal and healthy pregnancy.

The types of tests needed for an anembryonic pregnancy are: 1. Pregnancy test: This test checks for the presence of the hormone human chorionic gonadotropin (hCG) in either a urine or blood sample. 2. Ultrasound examination: An ultrasound can be performed either transabdominally or transvaginally. In an anembryonic pregnancy, the ultrasound typically shows an "empty" gestational sac without an identifiable embryo. To confirm an anembryonic pregnancy, the ultrasound should show no identifiable embryo in a gestational sac that is 25 millimeters or larger in diameter. Additionally, if no embryo is seen in an ultrasound done more than 11 days after an earlier scan showed a gestational sac with a yolk sac but no embryo, or if no embryo is seen more than two weeks after a scan showed a gestational sac without any embryo or yolk sac, it can also confirm the diagnosis.

Anembryonic Pregnancy, also known as a blighted ovum, is a type of early pregnancy loss where the gestational sac develops without an embryo. The treatment options for anembryonic pregnancy are similar to those for other types of early pregnancy loss. They include expectant management, medical management, and surgical treatment. Expectant management involves closely monitoring the patient without any medical intervention, allowing the pregnancy tissue to pass naturally. Medical management involves the use of medications like mifepristone and/or misoprostol to help the tissue pass. Surgical treatment involves uterine evacuation with a manual vacuum or dilation and curettage. The choice of treatment for anembryonic pregnancy is determined through collaboration between the patient and the physician, after a detailed discussion of the pros and cons of each method.

The prognosis for an anembryonic pregnancy, where a sac forms in the womb but no embryo develops, varies based on factors such as the progression of the pregnancy. Generally, all three treatment options (expectant management, medical management, and surgical treatment) are considered effective. Surgical treatment has been found to have a higher success rate compared to medical treatment, but both options are generally safe.

You should see an obstetrician or a gynecologist for an anembryonic pregnancy.

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