Missed Miscarriage, Blighted Ovum, and Chemical Pregnancy

According to the American Academy of Pediatrics, a majority of pregnancies never go past the first few weeks, and even after a clinical diagnosis of pregnancy (using ultrasound), there's still about a 25 percent chance of miscarriage. Many miscarriages occur so early in the pregnancy that the woman may not have even been aware she was pregnant. The following are three common types of early miscarriages.

Missed Miscarriage

A missed miscarriage is a type of spontaneous abortion (the clinical term for any loss of any pregnancy prior to the 20th week) in which the fetus dies but the fetal tissue is not expelled by the woman's body and remains there until it is removed by a doctor. If the placenta continues to release hormones, the woman will still experience all the signs and symptoms of being pregnant; however some women notice that their pregnancy symptoms (nausea, breast tenderness, fatigue, etc.) disappear and some may notice a brownish or bright red vaginal discharge along with some cramping. Because this type of miscarriage, often referred to as a "silent miscarriage," often has no symptoms, many women don't discover their pregnancy has ended until they have a routine check-up and an ultrasound shows an underdeveloped fetus and the doctor cannot locate a fetal heartbeat.

Doctors usually can determine approximately when the fetus died by measuring its size. Once a fetus dies, it begins shrinking at the same rate it would have grown had the pregnancy continued. For example, if a fetus died at 11 weeks but it was not discovered until week 13, the fetus would have shrunk to approximately the size it would have been at week 9.

The earlier in the pregnancy that the miscarriage occurred, the more likely that the woman's body will eventually expel all the fetal tissue by itself, and she will not require further medical procedures. However, if the fetal tissue remains in the woman's body, it can cause serious infection and/or complications with blood clotting. In these cases a dilation and curettage, or D&C, is usually performed to remove the placental tissues, stop bleeding, and prevent infection.

Approximately 1 percent of pregnancies result in missed miscarriage, which usually occur due to chromosomal abnormalities of the fetus, rather than anything the mother did or didn't do. However, if a woman has more than three spontaneous abortions she should see a fertility specialist to ensure there is not some underlying cause.

Blighted Ovum

A blighted ovum, or embryonic pregnancy, occurs when an egg is fertilized and implants in the uterus, and the placenta and membrane begin developing, but a fetus fails to form or stops developing very early on causing the pregnancy to miscarry, usually between 7 and 12 weeks. A blighted ovum often happens so early in a pregnancy that the woman never knew she was pregnant.

This type of miscarriage is usually diagnosed using ultrasound, which will show a large gestational sac, but no embryo. Many doctors use the term "early pregnancy failure," instead of "blighted ovum" to describe this common type of miscarriage that accounts for approximately 50 percent of first trimester miscarriages. In some cases, a blighted ovum may occur in a twin pregnancy. In this instance, called a blighted twin, one of the fertilized eggs fails to develop properly while the second develops normally, completely unaffected by the blighted twin.

Because the placenta begins to develop and secrete human chorionic gonadotropin (hCG) in a blighted ovum, a pregnancy test will come back positive, even though no embryo is forming. The woman may also have some symptoms of a normal pregnancy early on, including fatigue, nausea, and sore breasts; however, hormone levels eventually begin to taper off causing the symptoms to subside and the woman to possibly notice some reddish-brown vaginal discharge, cramping, or bleeding.

The gestational sac and accumulated tissue is usually expelled by the end of the first trimester, if not earlier. However, the process of expelling the tissue completely can take weeks and many women opt to have a D&C once they find out their pregnancy has ended.

Chromosomal abnormalities usually cause a blighted ovum, and having one blighted ovum does not increase the risk of having another, and experts don't consider it a sign that there is anything wrong with either partner. However, if you have several consecutive miscarriages, your doctor may suggest testing to determine if there is something wrong.

Chemical Pregnancy

A chemical pregnancy is thought to occur when an egg is fertilized, but dies soon after implantation. A chemical pregnancy will cause a pregnancy test to come back positive, but only faintly so, and a blood test normally shows very low hCG levels that don't increase over time.

This type of early miscarriage is called a chemical pregnancy because a pregnancy is not considered "clinical" until it is confirmed with an ultrasound, usually around 5 or 6 weeks. A chemical pregnancy is similar to a blighted ovum and would become one if the pregnancy developed for several more weeks and a sac formed without the embryo.

Chemical pregnancies are thought to be fairly common, involving as many as half of all pregnancies, but an accurate number is hard to determine because most women who experience a chemical pregnancy never even realize they are pregnant unless they are trying to conceive and testing regularly and early. Most women assume their period was just a few days late and is unusually heavy; and they may also notice some small blood clots and unusual cramping. Many chemical pregnancies are discovered today that would otherwise have gone undetected due to the ultra sensitive pregnancy tests on the market, which make it easier to get a positive result 3 or 4 days before a woman's period is due.

Women who were aware that they were pregnant before the miscarriage should be monitored to ensure their hCG levels go down to pre-pregnancy levels. There is the possibility of an ectopic pregnancy, so it is necessary to ensure that a full miscarriage has occurred (all the fetal tissue is expelled), even if the woman has had a period.

Most chemical pregnancies are due to chromosomal problems in the developing fetus. Other possible causes include inadequate uterine lining, uterine abnormalities, low hormone levels, luteal phase defect, or certain infections. There is no way to prevent chemical pregnancies; however, your doctor may suggest you take vitamin B6 and baby aspirin, and apply progesterone cream, all of which can help lower the risk. If your doctor determines that an infection caused the chemical pregnancy, he or she may prescribe antibiotics to clear the infection and reduce the likelihood of another such miscarriage.