Spontaneous abortion (also known as miscarriage) is the expulsion of an embryo or fetus due to accidental trauma or natural causes before approximately the 22nd week of gestation; the definition by gestational age varies by country. Most miscarriages are due to incorrect replication of chromosomes; they can also be caused by environmental factors. A pregnancy that ends before 37 weeks of gestation resulting in a live-born infant is known as a "premature birth". When a fetus dies in utero after about 22 weeks, or during delivery, it is usually termed "stillborn". Premature births and stillbirths are generally not considered to be miscarriages although usage of these terms can sometimes overlap.
Between 10% and 50% of pregnancies end in clinically apparent miscarriage, depending upon the age and health of the pregnant woman. Most miscarriages occur very early in pregnancy, in most cases, they occur so early in the pregnancy that the woman is not even aware that she was pregnant. One study testing hormones for ovulation and pregnancy found that 61.9% of conceptuses were lost prior to 12 weeks, and 91.7% of these losses occurred subclinically, without the knowledge of the once pregnant woman.
The risk of spontaneous abortion decreases sharply after the 10th week from the last menstrual period (LMP). One study of 232 pregnant women showed "virtually complete [pregnancy loss] by the end of the embryonic period" (10 weeks LMP) with a pregnancy loss rate of only 2 percent after 8.5 weeks LMP.
The most common cause of spontaneous abortion during the first trimester is chromosomal abnormalities of the embryo/fetus, accounting for at least 50% of sampled early pregnancy losses. Other causes include vascular disease (such as lupus), diabetes, other hormonal problems, infection, and abnormalities of the uterus. Advancing maternal age and a patient history of previous spontaneous abortions are the two leading factors associated with a greater risk of spontaneous abortion. A spontaneous abortion can also be caused by accidentaltrauma; intentional trauma or stress to cause miscarriage is considered induced abortion orfeticide.
2. Induced
A pregnancy can be intentionally aborted in many ways. The manner selected depends chiefly upon the gestational age of the embryo or fetus, which increases in size as the pregnancy progresses. Specific procedures may also be selected due to legality, regional availability, and doctor-patient preference. Reasons for procuring induced abortions are typically characterized as either therapeutic or elective. An abortion is medically referred to as therapeutic when it is performed to:
• save the life of the pregnant woman;
• preserve the woman's physical or mental health;
• terminate pregnancy that would result in a child born with a congenital disorder that would be fatal or associated with significant morbidity; or
• selectively reduce the number of fetuses to lessen health risks associated with multiple pregnancy.
An abortion is referred to as elective when it is performed at the request of the woman "for reasons other than maternal health or fetal disease."
3. Medical
"Medical abortions" are non-surgical abortions that use pharmaceutical drugs. Medical abortions comprise 10% of all abortions in the United States and Europe . Combined regimens includemethotrexate or mifepristone, followed by a prostaglandin (either misoprostol or gemeprost: misoprostol is used in the U.S. ; gemeprost is used in the UK and Sweden
4. Surgical
A vacuum aspiration abortion at eight weeks gestational age (six weeks after fertilization).
a. Amniotic sac
b. Embryo
c. Uterine lining
d. Speculum
e. Vacurette
f. Attached to a suction pump
In the first 12 weeks, suction-aspiration or vacuum abortion is the most common method.Manual vacuum aspiration (MVA) abortion consists of removing the fetus or embryo,placenta and membranes by suction using a manual syringe, while electric vacuum aspiration(EVA) abortion uses an electric pump. These techniques are comparable, and differ in the mechanism used to apply suction, how early in pregnancy they can be used, and whether cervical dilation is necessary. MVA, also known as "mini-suction" and "menstrual extraction", can be used in very early pregnancy, and does not require cervical dilation. Surgical techniques are sometimes referred to as 'Suction (or surgical) Termination Of Pregnancy' (STOP). From the 15th week until approximately the 26th, dilation and evacuation (D&E) is used. D&E consists of opening the cervix of the uterus and emptying it using surgical instruments and suction.
Dilation and curettage (D&C), the second most common method of abortion, is a standard gynecological procedure performed for a variety of reasons, including examination of the uterine lining for possible malignancy, investigation of abnormal bleeding, and abortion. Curettagerefers to cleaning the walls of the uterus with a curette. The World Health Organizationrecommends this procedure, also called sharp curettage, only when MVA is unavailable.
Other techniques must be used to induce abortion in the second trimester. Premature delivery can be induced with prostaglandin; this can be coupled with injecting the amniotic fluid with hypertonic solutions containing saline or urea. After the 16th week of gestation, abortions can be induced by intact dilation and extraction (IDX) (also called intrauterine cranial decompression), which requires surgical decompression of the fetus's head before evacuation. IDX is sometimes called "partial-birth abortion," which has been federally banned in the United States
From the 20th to 23rd week of gestation, an injection to stop the fetal heart may be used as the first phase of the surgical abortion procedure to ensure that the fetus is not born alive.
Other methods
Historically, a number of herbs reputed to possess abortifacient properties have been used infolk medicine: tansy, pennyroyal, black cohosh, and the now-extinct silphium (see history of abortion). The use of herbs in such a manner can cause serious—even lethal—side effects, such as multiple organ failure, and is not recommended by physicians.
Abortion is sometimes attempted by causing trauma to the abdomen. The degree of force, if severe, can cause serious internal injuries without necessarily succeeding in inducing miscarriage. Both accidental and deliberate abortions of this kind can be subject to criminal liability in many countries. In Southeast Asia, there is an ancient tradition of attempting abortion through forceful abdominal massage. One of the bas reliefs decorating the temple of Angkor Wat in Cambodia
Reported methods of unsafe, self-induced abortion include misuse of misoprostol, and insertion of non-surgical implements such as knitting needles and clothes hangers into the uterus. These methods are rarely seen in developed countries where surgical abortion is legal and available.
