I was blissfully pregnant until three days ago. I had to have a D&C because at a term of eight weeks, I started spotting, and my OB found through vaginal ultrasound that I had "anembryonic gestation" -- a conception implanted with no growing fetus. The doctor said this is sometimes called "blighted ovum." The gestational sac was intact and growing at the rate it would have been if there were a fetus. My husband and I are devastated, as is our seven-year-old son. What causes this? How common is it? What are the chances of it happening again? None of my friends had ever heard of this condition, and neither had I.

Rhonda

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.

Following the first miscarriage, there is no need to test the parents for chromosomal problems. In fact, most physicians will not recommend genetic testing of the fetal products of conception unless and until there is a second loss. There is always an underlying risk of miscarriage, and a single first- trimester pregnancy loss does not change that risk. This risk does increase with age, however, so that in women between the age of 40-45, the risk of miscarriage can reach 65 percent. If you are over 35, I would strongly recommend asking your doctor to test your ovarian reserve to make sure that age-related infertility is not a factor.