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Blighted ovum

Blighted ovum
When applied to pregnancy, the term "blighted" sounds awful - cruel, even. Blighted ovum refers to an "anembryonic gestation" - a pregnancy that begins to grow in the absence of an embryo. This results in early miscarriage.

It is extremely common, occurring in up to 20 percent of known pregnancies.

The term blighted ovum refers to a fertilized egg (ovum) that has developed a placenta and membrane but no embryo. It occurs in the first few weeks of pregnancy - often before a woman even knows she's pregnant.

An ultrasound will show an empty placenta. It's thought to be due to a chromosomal abnormality.

Understanding the Process

To understand the reason for the "blight," let's go back to the beginning of the pregnancy process - conception. When egg and sperm meet, each contributes half the chromosomes that complete the fertilized egg and let it form an embryo. For a pregnancy to be viable, these chromosomal units must meet, combine and replicate perfectly.
This complicated process is not always successful. More than 60 percent of first-trimester losses are due to an improper pairing of chromosomes.

However, even when the pairing is unsuccessful, trophoblastic cells (which create the placenta and cause pregnancy tests to be positive) can develop and grow. The pregnancy hormone (HCG), which these cells secrete, makes you miss a period. Levels of HGC may continue to rise, though not as fast as with a normal pregnancy, so you may initially feel many of the sensations of pregnancy, including breast tenderness and nausea. These hormones will also indicate a positive result on your pregnancy test.

Because a true pregnancy has not occurred, you eventually will start to bleed and pass the products of conception. This can occur from a few days to weeks after the initial positive pregnancy test.

What is a blighted ovum?

A blighted ovum (also known as "anembryonic pregnancy") happens when a fertilized egg attaches itself to the uterine wall, but the embryo does not develop. Cells develop to form the pregnancy sac, but not the embryo itself. A blighted ovum usually occurs within the first trimester before a woman knows she is pregnant. A high level of chromosome abnormalities usually causes a woman's body to naturally miscarry.

What causes a blighted ovum?

While the term "blighted ovum" is not commonly known, the occurrence is quite common. A blighted ovum is a pregnancy in which the placenta develops but no fetus is visible on ultrasound. The fact that transvaginal ultrasound did not show an embryo at eight weeks must be viewed with caution. If the ultrasound had been performed earlier - say, at four to six weeks - it's very likely that either the fetus or yolk sac may have been seen. In other words, the presence or absence of an embryo at the time of the pregnancy loss has little bearing on future pregnancy outcomes.

Blighted ovum is thought to be due to a chromosomal abnormality. Over 60 percent of all first-trimester pregnancy losses are due to chromosomal abnormalities unique to that pregnancy - meaning that these are one-time events that do not raise the risk of similar future problems.

Usually the chromosomal abnormality lies in the individual egg; sperm chromosomal anomalies are infrequent. Other chromosomal problems may also arise if something goes awry genetically during the first few cell divisions of the newly formed embryo.

A woman's body recognizes abnormal chromosomes in a fetus and naturally does not try to continue the pregnancy because the fetus will not develop into a normal, healthy baby. This can be caused by abnormal cell division, or poor quality sperm or egg.

How do I know if I am having or have had a blighted ovum?

A blighted ovum can occur very early in pregnancy, before most women even know that they are pregnant. You may experience a missed or late menstrual period, minor abdominal cramps, minor vaginal spotting or bleeding, and a possible positive pregnancy test. As with a normal period, your body may flush the uterine lining but your period may be a little heavier then usual.

Many women assume their pregnancies are on track. The placenta can continue to grow and support itself without a baby for a short time and pregnancy hormones can continue to rise which would lead a woman to believe she is still pregnant. A diagnosis is usually not made until an ultrasound tests shows either an empty womb or an empty birth sac.

Natural miscarriage or?

This is a decision only you can make for yourself.

A blighted ovum will eventually result in miscarriage, although this may not occur for several weeks. Because waiting for a miscarriage can be distressing, a doctor may offer the option of a procedure called D&C (dilation and curettage) to remove the placental tissues.

Most doctors do not recommend a D&C for an early pregnancy loss. It is believed that a woman's body is capable of passing tissue on its own and there's no need for an invasive surgical procedure with a risk of complications. A D&C would, however, be beneficial if you were planning on having a pathologist examine the tissues to determine a reason for the miscarriage. Some women feel a D&C procedure helps with closure, mentally and physically.

For older women, the risk of miscarriage, including blighted ovum, increases, probably because older eggs have been spending lots of time incurring chromosomal damage. If this type of early miscarriage does recur, especially if you are under 35, your doctor may want to do genetic blood tests to look at possible chromosomal abnormalities in you and your partner.

If your pregnancy ends early due to a blighted ovum, don't despair. If you try again, you will probably have a successful pregnancy.

Most women who have had one miscarriage go on to have successful pregnancies. If you have two consecutive miscarriages in the first trimester, your doctor may recommend testing to try to determine the cause.


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