A blighted ovum, also called an anembryonic pregnancy occurs when a gestational sac develops without an embryo — often due to chromosomal abnormalities in the fertilized egg.
A blighted ovum usually occurs in the first few weeks of pregnancy, often before a woman even knows she's pregnant. However, a woman might miss a period and have a positive pregnancy test. This is because the placenta secretes human chorionic gonadotropin (HCG), a pregnancy hormone. Symptoms of early pregnancy — such as breast tenderness — are possible as well. But when the placenta stops growing and hormone levels decrease, the pregnancy symptoms subside. At this point, minor abdominal cramping and light spotting or bleeding are possible. An ultrasound will show an empty gestational sac.
A blighted ovum eventually results in miscarriage. Some women choose to wait for the miscarriage to happen naturally, while others take medication to trigger the miscarriage. In some cases, a procedure called dilation and curettage (D&C) is used to remove the placental tissues.
Most women who've had a blighted ovum go on to have successful pregnancies. If you experience multiple consecutive miscarriages, you might consider testing to identify any underlying causes.
Mary M. Gallenberg, M.D. (2013). What causes a blighted ovum? Mayo Clinic [Online]. Available: http://www.mayoclinic.org/diseases-conditions/pregnancy-loss-miscarriage/expert-answers/blighted-ovum/faq-20057783 [August 23, 2013]