A 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 implantation occurs and early embryonic development may begin, the embryonic tissue stops developing at a very early stage, leaving behind an empty gestational sac. Because the gestational sac cannot progress or resolve on its own, medical management is required, most commonly through a dilation and curettage (D&C) procedure to remove the nonviable pregnancy tissue.
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A blighted ovum (also known as an anembryonic pregnancy) is a type of abnormal pregnancy that occurs when an egg and sperm are fertilized but the embryo fails to develop properly. Although implantation occurs in the early stages of pregnancy, the embryonic tissue stops developing at a very early stage, leaving only an empty gestational sac without a viable embryo.
Because the pregnancy cannot progress normally, a dilation and curettage (D&C) procedure is usually required to remove the gestational tissue from the uterus.
Causes of Blighted Ovum
Approximately 50% of blighted ovum cases are caused by chromosomal abnormalities in the embryo, which occur naturally. Blighted ovum can happen to women of any age; however, the risk increases significantly with maternal age.
The approximate risk of blighted ovum by age group is as follows:
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Women under 35 years old: approximately 15% risk
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Women aged 35–38 years: increased risk of 20–25%
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Women aged 39–40 years: approximately 30% risk
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Women over 40 years old: approximately 35–40% risk
As shown above, the likelihood of blighted ovum is strongly associated with maternal age. As women age, the genetic quality of their eggs declines. When such eggs are fertilized, the resulting embryos are more likely to have chromosomal abnormalities, such as missing chromosomes or extra copies of one or more chromosomes. These abnormalities can prevent normal embryonic development, leading to a blighted ovum.
From the image above, we can observe an empty gestational sac with no visible fetus. This occurs when embryonic development stops at a very early stage of pregnancy, leaving only the gestational sac and surrounding structures, such as the placenta and amniotic sac, without an embryo.
A blighted ovum (also known as an anembryonic pregnancy) is a naturally occurring condition that can happen during early pregnancy. It results from a fertilized egg that successfully implants in the uterus but fails to develop into an embryo. This is most commonly due to chromosomal abnormalities in the egg, which occur spontaneously and are not caused by external factors.
Although fertilization takes place and the gestational sac begins to form, the embryo does not continue to grow. As a result, the pregnancy may initially appear normal, with signs such as a missed menstrual period and a positive pregnancy test. However, during an ultrasound examination at approximately 6–7 weeks of gestation, only an empty gestational sac is seen, with no visible embryo or fetal 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 risk of recurrence in a subsequent pregnancy is generally consistent with age-related risk.
However, when blighted ovum occurs more than once, the risk of recurrence becomes significantly higher. In such cases, the cause may not be due solely to random chromosomal abnormalities. One partner may carry an inherited chromosomal rearrangement that can be passed on to the embryo, interfering with normal development.
Can a Blighted Ovum Occur with Assisted Reproductive Technologies (ART)?
Yes. A blighted ovum can occur in both natural pregnancies and pregnancies achieved through assisted reproductive technologies, such as artificial insemination or in vitro fertilization (IVF). The risk remains closely related to maternal age and the genetic quality of both the egg and sperm.
Repeated occurrences of blighted ovum increase the likelihood of an underlying chromosomal abnormality in one of the parents.
When Should Further Investigation Be Performed?
If a woman experiences two or more blighted ovum pregnancies, further medical evaluation is recommended. One possible underlying cause is a genetic condition known as balanced translocation. In this condition, one partner carries a rearrangement of chromosomes but has no physical symptoms or health problems.
A chromosomal analysis (karyotype) using a blood sample can determine whether either partner carries this type of chromosomal rearrangement. Karyotype images allow visualization of chromosomal structure and alignment.
In the referenced image, Figure A and Figure B represent normal chromosomal arrangements. The middle image illustrates a chromosomal abnormality involving the loss of genetic material from the lower arms of chromosomes. The image on the right demonstrates balanced translocation, in which segments of chromosomes are exchanged and attached to different chromosomes.
In individuals with balanced translocation, the total number of chromosomes remains normal, but their structure and position are altered. This does not cause illness or physical abnormalities in the carrier. However, during the formation of egg or sperm cells, these rearranged chromosomes may segregate unevenly, resulting in eggs or sperm with missing or extra chromosomal material.
When such imbalanced genetic material is passed to an embryo, normal development cannot be sustained, often leading to early pregnancy loss, including blighted ovum or miscarriage.
Chromosomal Abnormalities Caused by Balanced Translocation
When one partner carries a balanced translocation, there is approximately a 50% chance that the resulting embryos will have chromosomal abnormalities. Statistically, among all pregnancies:
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Only 1 in 4 embryos is expected to be genetically normal
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Another 1 in 4 embryos may inherit the same balanced translocation as the affected parent
Although individuals who inherit a balanced translocation often appear physically healthy and have no symptoms, they can pass this chromosomal rearrangement on to future generations, potentially leading to reproductive difficulties.
Preventing Chromosomal Abnormalities Through Preimplantation Genetic Testing
Most chromosomal abnormalities occur naturally, particularly as a result of advanced 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 analyzing each embryo for chromosomal abnormalities before implantation, doctors can select embryos with a normal chromosomal complement, thereby improving the likelihood of a healthy pregnancy and reducing the risk of miscarriage.
Symptoms of a Blighted Ovum
A blighted ovum often presents with symptoms similar to those of a normal early pregnancy because the body continues to produce human chorionic gonadotropin (hCG). However, hCG levels are usually lower than expected, which may result in milder symptoms.
Common symptoms include:
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Missed menstrual periods
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Breast tenderness
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Mild nausea
Some women may experience few or no noticeable pregnancy symptoms at all.
Diagnosing a Blighted Ovum
A blighted ovum is typically diagnosed by ultrasound examination between the 6th and 7th week of pregnancy. During the scan, the physician evaluates the presence and size of the gestational sac within the uterus.
If the gestational sac measures greater than 17–20 mm with no visible fetal pole, this raises concern for a blighted ovum. To ensure diagnostic accuracy, a follow-up ultrasound after 1–2 weeks is usually recommended, as early embryonic development can vary among pregnancies.
If the repeat ultrasound continues to show an empty gestational sac without an embryo or fetal heartbeat, the diagnosis of a blighted ovum is confirmed.
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