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Your guide to blighted ovum misdiagnosis

Crying woman being comforted by man - blighted ovum misdiagnosis

During the first few weeks of pregnancy, the misdiagnosis of a blighted ovum is possible if the date of conception is uncertain. Although the developing embryo typically becomes visible earlier on a transvaginal ultrasound scan, it is not visible on an abdominal ultrasound scan until 1 - 2 weeks later.

Following a positive pregnancy test or a missed period, an expectant mother with a blighted ovum can still feel pregnantbecause her levels of the ‘pregnancy hormone’, hCG, may remain high for some time after the embryo has stopped developing and is no longer present.

Pelvic ultrasound scans

If you are uncertain about your date of conception, dates your GP should arrange for pelvic ultrasound scans to be carried out after a recommended number of weeks to avoid the possibility of misdiagnosis.

There are set guidelines for correctly diagnosing a blighted ovum, based on the recorded measurements of the embryo within the gestational sac when each type of ultrasound scan is carried out.

Seeking answers for a misdiagnosis requires specialist knowledge of both legal and medical issues. Clinical negligence cases involving pregnancy and child birth naturally demand the highest degree of sensitivity and understanding of how everyone involved is affected.

Our dedicated team of specialist solicitors have many years of experience in successfully resolving different types of clinical negligence cases, so we can help you:

  • Find out the reason why something went wrong with a diagnosis, treatment or procedure.
  • Obtain financial compensation for the injury or harm caused.

How common is a blighted ovum?

  • Around 15% of all clinically recognised pregnancies end in miscarriage.
  • Between 45 – 55% of all miscarriages are caused by a blighted ovum
  • Up to 60% of miscarriages caused by a blighted ovum occur in the first three months of pregnancy.
  • 67% of genetic samples taken from blighted ovum miscarriages contain abnormal chromosomes.

What is a blighted ovum?

The medical term for a blighted ovum is an anembryonic gestation, the most common cause of an early miscarriage in the first trimester, i.e. the first three months of pregnancy. 

A blighted ovum is a fertilised egg, attached to the wall of the womb, which does not develop beyond implantation. The gestational sac continues to grow but the baby does not grow within the sac and is reabsorbed. In the case of a true blighted ovum, the yolk and foetal pole - the early thickening on the margin of the yolk sac - will not be present.

What is the cause of a blighted ovum?

Chromosome abnormalities are known to be a major cause of a blighted ovum, which occurs for many reasons including: 

  • Chromosomes, which form a developing foetus, become defective or disordered during division of the fertilised egg.
  • Egg or sperm which have joined during fertilisation possess defective cells.
  • A blighted ovum may be more common in older mothers and is usually a problem with the egg rather the sperm.
  • The body recognises the chromosomal abnormalities and reacts by ending the pregnancy.

Diagnosing a blighted ovum

Detection of the developing embryo is carried out by pelvic or gynaecologic ultrasound scans, which examine the female pelvic organs including, the “womb” / uterus, the lining of the uterus, the cervix and the ovaries.

Most pelvic ultrasounds are performed using both transabdominal and transvaginal scans.

  • Transvaginal ultrasound scan – taken between 5 to 6 weeks of pregnancy.

An internal scan that usually produces better and clearer images of the female pelvic organs.)

  •  Abdominal ultrasound scan – taken between 6 to 7 weeks of pregnancy.

Scans through the lower abdomen to provide an overview of the pelvis rather than detailed images. It is used particularly for examining large pelvic masses extending into the abdomen, but is not always as clear as a transvaginal ultrasound.

When performing the above scans, the factors for a diagnosis of blighted ovum are:

  • Transvaginal ultrasound: Failure to identify an embryo in a gestational sac measuring around 18mm or more.
  • Transabdominal ultrasound: Failure to identify an embryo in a gestational sac measuring at least 20 mm.
  • At an earlier stage there can also be a failure to identify a yolk sac in a gestational sac measuring 13mm or more.

Avoiding an early misdiagnosis

As the yolk sac of the growing embryo may not always be found within the gestational sac until the sac becomes larger, doctors are recommended to wait before proceeding with a diagnosis until the sac diameter is at least 25mm with no embryo visible or an embryo without a detectable heartbeat. Repeat scans should be performed if measurements are close to the cut-off values of 21mm.

A transvaginal exam may not always be performed at the mother’s initial visit. Instead, a transabdominal examination is carried out and a follow-up ultrasound 10 days later to see if a normal pregnancy subsequently develops.

Further complications

The retroverted uterus

While the uterus usually tilts slightly forward toward the stomach, around 20 to 40% of all women have a retroverted uterus. This is where the uterus tilts back toward the rectal area, which could cause a difficulty in detecting the embryo using transvaginal ultrasound.

However, measurements are generally more accurate in women with a tilted uterus during the second trimester, i.e. between 3-6 months.

“Pregnancy hormone” (hCG)

hCG is a hormone produced by the placenta as soon as implantation in the womb occurs, usually around one week after fertilisation and ovulation. hCG levels continue to rise until around 10-12 weeks gestation, at which point the hCG level will stabilise or fall.

A pregnancy test detects the amount of hCG in the blood or urine, with a positive result when there are sufficient levels of hCG. However as hCG levels can change and rise even when there is an empty gestational sac, this test can be unreliable in the case of a blighted ovum.

The miscarriage

A miscarriage is needed to expel the gestational sac and accumulated tissue by the end of the first three months, although it can take place earlier.

When the diagnosis of a blighted ovum is confirmed, a woman can safely wait to miscarry naturally if she is stable and there is no excessive pain, bleeding or fever. 

Future pregnancy

A blighted ovum is considered a one-time event. While miscarriage is a risk in any pregnancy, the risk is not increased because of the blighted ovum but it also does not mean that a miscarriage cannot occur again.

How Your Legal Friend can help you

As experienced clinical negligence specialists, we know that you will want to find out if your GP, doctor or specialist failed you or a family member in their duty to provide the expected standard of care and treatment in the diagnosis of a blighted ovum.

We ensure your case is properly investigated and your voice heard in order to bring the hospital, health trust or medical practitioner to account for any harm and suffering they have caused.

Your Legal Friend is committed to ensuring that victims of medical negligence obtain answers and receive appropriate compensation so that their current and future medical treatment and care needs are properly met.