spontaneous abortion, pregnancy loss, fetal loss
Miscarriage is the death of an embryo or fetus before it is able to survive independently. Some use the cutoff of 20 weeks of gestation (carrying of an embryo or fetus), after which fetal death is known as a stillbirth (Pic. 1).
Miscarriage is the most common complication of early pregnancy. About 30% to 40% of all fertilized eggs miscarry, often before the pregnancy is known. These are often termed preclinical losses. Among women who know they are pregnant, the miscarriage rate is roughly 10% to 20%.
Most clinically apparent miscarriages (two-thirds to three-quarters in various studies) occur during the first trimester. Signs of a miscarriage include vaginal spotting, abdominal pain or cramping, and fluid or tissue passing from the vagina. Bleeding can be a symptom of miscarriage, but many women also have bleeding in early pregnancy and don't miscarry. Bleeding during pregnancy may be referred to as a threatened miscarriage. Of those who seek clinical treatment for bleeding during pregnancy, about half will miscarry.
Miscarriage can be classified as threatened, inevitable, incomplete, complete (Pic. 2), missed, or recurrent. Any type of miscarriage other than recurrent is also termed solitary miscarriage.
Threatened miscarriage is defined as vaginal bleeding before 20 weeks gestation in the presence of a viable fetus. One in five pregnancies will present in this manner and these pregnancies are 2.6 times more likely to result in complete miscarriage. Patients usually present with little to no pain, slight blood loss of fresh bloods with clots or brown staining, possibly present fetal movements and no passing of products of conception (fetal and/or placental tissues). Upon examination, uterine size is normal for dates, the uterine cervix is closed, fetal movements and heart sounds are present.
In inevitable miscarriage, the cervix has begun to open and some products of have passed, therefore, the pregnancy cannot be saved and miscarriage is inevitable. The patients have a history of heavy bleeding getting worse, severe colicky abdominal pain and passing of products of conception. Upon examination, the uterine cervix is open and products of conception may be passing through its orifice.
This is defined as the return to normal uterine size after the passage of all products of conception and normally occurs before 8 weeks gestation.
This is most common between 8 and 14 weeks gestation. All the products of conception have not been passed and the patient requires evacuation of the retained products of conception.
The patient may, similarly to an inevitable miscarriage, suffer from heavy bleeding and severe colicky abdominal pain. Upon examination, the uterine cervix is open and products of conception may be passing through its orifice.
A missed (or silent) miscarriage is the spontaneous abortion of a pregnancy in the absence of vaginal bleeding. In essence, the fetus is dead in utero (inside the uterus). There are no fetal movements present and no fetal heart sounds.
Recurrent miscarriage is generally defined as spontaneous abortions repeated consecutively over three or more times. The incidence ranges from 2% to 4%, of which nearly 80% appear in the first trimester. The majority of patients are counselled to try to conceive again, and chances are about 60% that the next pregnancy is successful without treatment.
Causes of miscarriage
Miscarriage may occur for many reasons, not all of which can be identified. Many risk factors that may contribute to an increased chance of a miscarriage have been identified, but their significance is usually not fully understood. Up to 70 conditions, infections, medical procedures, lifestyle factors, occupational exposures, chemical exposure, and shift work are associated with increased risk for miscarriage. Some of these risks include endocrine, genetic, uterine, or hormonal abnormalities, reproductive tract infections, and tissue rejection caused by an autoimmune disorder. The age of the pregnant woman is a significant risk factor. Miscarriage rates increase steadily with age, with more substantial increases after age 35 (Pic. 3). In those under the age of 35 the risk is about 10% while it is about 45% in those over the age of 40. Risk begins to increase around the age of 30.
Typical causes of early miscarriage
Early miscarriages can be due to a developmental abnormality of the placenta or other embryonic tissues. In some instances an embryo does not form but other tissues do. This has been called a "blighted ovum" (Pic. 4). Chromosomal abnormalities (Pic. 5) are found in more than half of embryos miscarried in the first 13 weeks. Half of embryonic miscarriages (25% of all miscarriages) have an aneuploidy (abnormal number of chromosomes). Common chromosome abnormalities found in miscarriages include autosomal trisomy (22-32%), monosomy X (5-20%), triploidy (6-8%), tetraploidy (2-4%), or other structural chromosomal abnormalities (2%).Genetic problems are more likely to occur with older parents; this may account for the higher rates observed in older women.
Typical causes of later miscarriage
Second trimester losses may be due to maternal factors such as uterine malformation, growths in the uterus (fibroids), or cervical problems. These conditions also may contribute to premature birth. Unlike first-trimester miscarriages, second-trimester miscarriages are less likely to be caused by a genetic abnormality; chromosomal aberrations are found in a third of cases. Infection during the third trimester can also cause a miscarriage.
Women who miscarry early in their pregnancy usually do not need any subsequent medical treatment. They can benefit from support and counselling. Most early miscarriages will complete on their own; in other cases, medication treatment or aspiration of the products of conception can be used to remove remaining tissue. While bed rest has been advocated to prevent miscarriage, this has not been found to be of benefit. Those who are or who have experienced an abortion benefit from the use of careful medical language. Significant distress can often be managed by the ability of the clinician to clearly explain terms without suggesting that the woman or the couple are somehow to blame.
For women who experience only one miscarriage and who have no other associated major risk factors, the risk of adverse outcomes of future pregnancies is quite low and they have approximately 85% chance that their next pregnancy will be completely normal. After a miscarriage, the woman’s menstrual cycle returns to its normal state in about four to six weeks. After this period, the woman may again attempt to achieve a pregnancy. However, a more complex assessment of her health should be carried out by a gynaecologist, as it can take up to six months for her whole body to return to a completely healthy state after a miscarriage. Her psychological health should be also carefully assessed and any issues arising from the experienced miscarriage should be resolved before attempting to achieve another pregnancy.
Women with a history of RSA (recurrent spontaneous abortion) are exposed to higher rates of adverse maternal and fetal outcomes in their subsequent pregnancies. Patients who experienced more than 2 incidents of miscarriage are often exposed to elevated incidences of placental dysfunction disorders and cesarean section. Such patients should be considered as high risk obstetric population. Specific perinatal care and corresponding preventions of placenta diseases can be implemented to reduce the incidence of adverse pregnancy outcomes.
Some clinicians recommend that the women have one menstrual cycle before attempting another pregnancy. This is because the date of conception may be hard to determine. Also, the first menstrual cycle after a miscarriage can be much longer or shorter than expected. Parents may be advised to wait even longer if they have experienced late miscarriage, molar pregnancy or are undergoing tests. Some parents wait for six months based upon recommendations from their health care provider.
The risks of having another miscarriage vary according to the cause. The risk of having another miscarriage after a molar pregnancy is very low. The risk of another miscarriage is highest after the third miscarriage.
A condition when immune system mistakenly attacks some of the standard proteins in blood.
A medical condition, where the walls of the uterus stick to one another due to bands of scar tissue.
The finger like overgrowths attached to the inner wall of the uterus that extend into the uterine cavity which are made of endometrial tissue
A state in which pieces of the tissue alike to the lining of the uterus (endometrium) grow in other parts of the body.
An obstruction prevents the egg or sperm from traveling down the tube, thus making fertilization impossible.
An abnormal condition in a woman's menstrual cycle.
Infection of the upper part of the female reproductive system and a common complication of some sexually transmitted diseases.
The most common benign smooth muscle tumors of the uterus encountered in women of reproductive age.
The term PGS is used to denote procedures that do not look for a specific disease but to identify embryos at risk of de-novo occurring aneuploidies
Embryonic biopsy is taking cells from an embryo for further examination (PGD / PGS).