Blighted Ovum is a type of abnormal pregnancy in which a fertilized egg implants in the uterus but fails to develop into a fetus. Although an embryo initially forms and implantation occurs during the early stages of pregnancy, the embryonic tissue stops developing, leaving behind an empty gestational sac. As this sac does not develop further on its own, a medical procedure—typically dilation and curettage (D&C)—is required to remove it.
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Abdominal wind or molar pregnancy is a type of abnormal pregnancy that occurs when an egg and sperm combine to form an embryo. The embryo implants in the early stages, but the fetal tissue is lost before development, leaving only the gestational sac that does not develop on its own. Therefore, it is necessary for a doctor to perform a dilation and curettage procedure to remove it.
Causes of Blighted ovum
Approximately 50% of Blighted ovum cases are caused by abnormalities in the fetal chromosomes, which occur naturally. We find that in nature, abdominal wind can occur at any age of the mother. The chances of molar pregnancy occurring are as follows:
- Women under 35 years old have a 15% chance of having a natural molar pregnancy.
- Women aged 35-38 years have an increased risk of molar pregnancy, ranging from 20-25%.
- Women aged 39-40 years have a 30% risk of molar pregnancy.
- Women over 40 years old have a 35-40% risk of molar pregnancy.
As we can see, the likelihood of molar pregnancy is related to age. As women get older, the normal genetic characteristics of the eggs decrease. This means that when the egg is fertilized by sperm, the resulting embryo may have an abnormal number of chromosomes, either missing or having an extra pair or multiple pairs simultaneously.
From the image above, we can observe that there is only an empty gestational sac with no visible fetus. This occurs because the fetal tissue has stopped developing at an early stage, leaving behind only the placenta and amniotic sac.
A blighted ovum is a naturally occurring condition that can happen during early pregnancy.
It results from a fertilized egg that implants in the uterus but fails to develop into an embryo. This is usually due to chromosomal abnormalities in the egg, which occur naturally. Although fertilization may take place and the gestational sac may begin forming, the embryo does not continue to grow. As a result, the pregnancy may appear normal at first — including a missed period and positive pregnancy test — but during an ultrasound at around 6–7 weeks, only an empty gestational sac is found, with no visible embryo or heartbeat.
How often does a blighted ovum occur?
The likelihood of a blighted ovum increases with maternal age. If a woman experiences a blighted ovum during her first pregnancy, the chance of recurrence in the next pregnancy is generally based on age-related risk. However, if a blighted ovum occurs more than once, the risk of recurrence becomes significantly higher.
In such cases, the cause might not be due to random chromosomal errors alone. One partner may carry an inherited chromosomal abnormality that can be passed on to the embryo, preventing normal development.
Can a blighted ovum occur with assisted reproductive technologies (ART)?
Yes. A blighted ovum can occur in both natural pregnancies and those resulting from artificial insemination or in vitro fertilization (IVF). The risk remains dependent on the woman’s age and the quality of the egg and sperm. Frequent occurrences of blighted ovum raise the likelihood of underlying chromosomal abnormalities.
When should further investigation be done?
If a woman experiences two or more blighted ovum pregnancies, further investigation is recommended. One possible cause is a genetic condition known as balanced translocation, in which one partner carries a chromosomal rearrangement but has no visible physical symptoms. This condition can be passed to the embryo and may result in recurrent pregnancy loss.
A chromosome analysis (karyotype) using a blood sample can help determine whether either partner carries such a genetic condition. The sample image of chromosomes can assist in visualizing these abnormalities.
From the above image, Figure A and Figure B represent normal chromosomes. The middle image depicts a condition where there is a loss of chromosomes in both lower arms, and the right hand shows an example of balanced translocation chromosomes.
The image on the right-hand side shows chromosomes with missing parts joined together, but they are attached to the wrong chromosomes. In individuals with these rearrangements, the total number of chromosomes does not change; only their positions are altered. This does not have any impact on the body or cause any diseases. However, when having children, these rearranged chromosomes can undergo segregation to form egg and sperm cells, resulting in eggs or sperm with imbalanced chromosomal portions. This imbalance can affect the chromosomes of the embryo, leading to deficiencies or excesses. Ultimately, the affected embryos cannot sustain life and result in miscarriages.
Chromosomal Abnormalities Caused by Balanced Translocation
When one partner carries a balanced translocation, there is approximately a 50% chance of producing embryos with chromosomal abnormalities. Among all pregnancies, only 1 in 4 may result in a genetically normal fetus.
- Another 1 in 4 may inherit the same chromosomal rearrangement as the parent who carries the balanced translocation. While the child may appear physically normal, they can pass this chromosomal issue on to future generations.
- Preventing Chromosomal Abnormalities Through Preimplantation Genetic Testing
Chromosomal abnormalities are primarily caused by natural factors such as maternal age, and cannot always be prevented. However, in cases involving in vitro fertilization (IVF) or recurrent pregnancy loss, especially when one partner is known to carry a balanced translocation, preimplantation genetic testing (PGT) can significantly reduce the risk. - By screening each embryo for chromosomal abnormalities before implantation, doctors can select embryos with a normal number of chromosomes, improving the chances of a healthy pregnancy.
Symptoms of a Blighted Ovum
A blighted ovum often presents symptoms similar to a normal pregnancy because the body continues to produce the hormone hCG (human chorionic gonadotropin). However, hCG levels tend to be lower, which may cause fewer or milder symptoms.
Common symptoms include:
- Missed periods
- Breast tenderness
- Mild nausea
- Some women may not experience noticeable pregnancy symptoms at all.
Diagnosing a Blighted Ovum
A blighted ovum is usually diagnosed via ultrasound between the 6th and 7th week of pregnancy. During the scan, the doctor will look for a gestational sac in the uterus. If the sac measures more than 17–20 mm with no visible fetal pole, it raises concern.
A follow-up ultrasound within 1–2 weeks is typically recommended to confirm the diagnosis, as early embryonic development can vary. If the second scan still shows an empty gestational sac with no embryo or heartbeat, the diagnosis of a blighted ovum is confirmed.
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