Miscarriage

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Introduction0:00–0:13

A miscarriage, or spontaneous abortion, is defined as a pregnancy loss that occurs without outside intervention before the 20th week of pregnancy.

Chromosomal causes0:13–1:57

Pregnancy is so complex that there are many different ways for the process to get off course and for a miscarriage to occur.
For example, if there’s a chromosomal abnormality in the sperm or egg then the resulting zygote will have a problem. One of these problems is called aneuploidy, which is when there are missing chromosomes or additional chromosomes.
For example, if there’s one member of a chromosome pair missing, that results in 45 chromosomes total, instead of the normal 46, it’s called a monosomy.
And if there’s one extra chromosome joining a pair, that results in 47 chromosomes total, and it’s called a trisomy. Some types of aneuploidy are viable like Turner’s syndrome or Down syndrome, whereas many are not and lead to a miscarriage.
Another abnormality is polyploidy, and that’s when a zygote receives more than one set of 23 chromosomes from either the sperm or egg, resulting in three sets, totaling 69 chromosomes, or even four sets, totaling 92 chromosomes.
Polyploidy is generally not viable and leads to a miscarriage. One more abnormality is a translocation.
It can either be balanced, where two nonhomologous chromosomes essentially trade equal amounts of DNA, or unbalanced, where the chromosomes exchange unequal amounts of DNA, resulting in either too many or too few copies of certain genes on the involved chromosomes.
Now even if a parent carries a balanced translocation, the sperm or egg may end up with an unbalanced translocation, and the zygote won’t have a normal number of genes.
Some translocations are viable, whereas many are not, and can lead to a miscarriage. Now, let’s say that there are a normal number of chromosomes present, and that the zygote becomes a blastocyst and tries to implant, there are still many ways in which a miscarriage can occur.

Implantational causes1:57–2:41

First if the blastocyst fails to implant into the endometrial lining of the uterus, then it won’t find a blood supply and stops growing and get reabsorbed.
Secondly if the blastocyst implants in tissue other than the endometrial lining of the uterus, such as the Fallopian tube, it’s called an ectopic pregnancy.
In the majority of cases, ectopic pregnancies won’t have the space or blood supply necessary to support a developing pregnancy.
As a result, the blastocyst stops growing and is reabsorbed. If the blastocyst does implant in the endometrium and continues its development, it relies on the corpus luteum to maintain the pregnancy.

Placental causes2:41–3:15

And one hypothesis is that a miscarriage can occur if the corpus luteum fails to secrete enough progesterone. Finally, as the pregnancy continues and the placenta develops, the fetus begins to rely on the placenta to maintain the pregnancy.
If the placenta is unable to secrete sufficient levels of hormones or provide the fetus with a sufficient blood supply at any point, the fetus can stop growing and a miscarriage can occur.

Traumatic causes3:15–4:39

During the embryonic period, which is between the third and eighth week of pregnancy, the fetus is especially vulnerable to damage from teratogens, which refers to anything that disturbs normal development – potentially resulting in a birth defect or death of the fetus.
The list of environmental teratogens is long, and it includes things like medications such as isotretinoin, alcohol, recreational drugs like cocaine, tobacco smoke, and heavy metals like mercury.
Vital organs like the heart and brain are developing quickly during the embryonic period and teratogens can cause them to have severe abnormalities.
Between weeks 10 through 14 of pregnancy, chorionic villus sampling can be performed to assess the growing fetus. That’s when either a needle or a catheter is used to grab a small sample of the placenta, so that a genetic analysis can be done on fetal cells from the placenta.
Around week 15, amniocentesis can be performed instead of chorionic villus sampling. That’s when a needle is placed into the amniotic fluid, to pull out some fetal cells.
These procedures are usually well tolerated, but they both have a small risk of causing trauma and introducing an infection - both of which could lead to miscarriage.
Other traumatic causes of miscarriage include motor vehicle accidents and accidental falls. As the fetus grows throughout the pregnancy, uterine abnormalities can also become an issue.

Uterine causes4:39–5:03

For example, if there’s a septate uterus, which is where there’s a septum or thin flap of tissue within the uterine cavity, or if there’s a submucosal leiomyoma, also called a submucosal fibroid, then it limits the amount of space available for the growing fetus.
And this can lead to a miscarriage. In addition, bacteria like Listeria monocytogenes, protozoa like Toxoplasma gondii, or viruses like cytomegalovirus and herpes simplex virus might infiltrate the uterus or pass through the placenta to get to the growing fetus.

Infectious and maternal disease causes5:03–5:56

A severe fetal infection can lead to a miscarriage. Finally, various maternal diseases can also affect the fetus.
This includes obesity, endocrine disorders like diabetes mellitus, thyroid dysfunction, or PCOS, which stands for polycystic ovary syndrome, immune system disorders like antiphospholipid syndrome or systemic lupus erythematosus which can also increase the likelihood of blood clotting, and high blood pressure which damages blood vessels, including those of the placenta.
Increasing age of either parent is also a risk factor. The diagnosis of a miscarriage is based on the stage of the pregnancy.

Types of Miscarriage5:56–7:15

A threatened miscarriage or threatened abortion is what it’s called if there’s bleeding from a closed cervix, and an ultrasound confirms that the fetus is viable.
This occurs quite commonly in pregnancy, and most of the time it does not result in a miscarriage. Next, there’s an inevitable miscarriage, which is when bleeding comes from an open cervix.
This is typically accompanied by abdominal cramping pain and uterine contents like the placenta or fetus are often visible during pelvic examination.
After that, there’s an incomplete miscarriage which is when the uterine contents have begun to pass through the open cervix.
If the uterus becomes infected during this process, it’s called a septic abortion. That infection can spread from the genital tract to nearby structures and the bloodstream – resulting in a potentially life-threatening situation for the woman.
Finally, a complete miscarriage is when the uterine cavity is empty and the cervix has closed once again. Now, there is also something called a missed miscarriage, and that’s when the fetus is no longer viable, but the cervix has not opened to allow the passage of the placenta and fetus.
A missed miscarriage can occur with or without symptoms like bleeding or pelvic pain. Symptoms of a miscarriage depend on how far along the pregnancy is.

Symptoms7:15–7:45

A miscarriage in the first few weeks of pregnancy may go completely unnoticed, or may result in a relatively small amount of vaginal bleeding with or without the passage of embryonic material that appears like blood clots.
As the pregnancy gets further along, miscarriages are more likely to produce lower abdominal pain and more vaginal bleeding and passage of placental and fetal tissue, which are called products of conception.

Diagnosis7:45–7:59

Diagnosis of a miscarriage can be done using a transvaginal ultrasound, pelvic examination, and laboratory tests such as measuring the serum hCG levels to determine whether it’s appropriate for the gestational age.

Treatment7:59–9:00

Treatment of a missed, incomplete, or inevitable miscarriage may include expectant management, which involves close monitoring while the miscarriage goes to completion without medical intervention.
Sometimes medications like misoprostol can be used to induce labor, or surgical options like dilation and curettage or uterine aspiration can be done.
A complete miscarriage typically requires no medical intervention. Treatment of a septic miscarriage may include antibiotics and surgical intervention.
In many countries, women whose blood type is Rh(D) negative and who do not already have anti-D antibodies in their blood, are given Rh(D)-immune globulin when they have vaginal bleeding during pregnancy or soon after the diagnosis of a miscarriage.
This prevents the development of antibodies that can cause harm to future pregnancies. Lastly, social and mental health support are crucial for anyone affected by the miscarriage.

Review9:00–9:50

All right, as a quick recap... A miscarriage, or spontaneous abortion, is defined by many organizations as a pregnancy loss that occurs without outside intervention before the 20th week of pregnancy.
There are many known risk factors, including chromosomal abnormalities, teratogen exposure, increasing parental age, physical uterine abnormalities, autoimmune disorders like antiphospholipid syndrome, and severe trauma.
A very early miscarriage may produce no noticeable symptoms, while vaginal bleeding and lower abdominal pain become more common later as the pregnancy progresses.
Treatment may include expectant management, surgery, or medications to induce labor.