Recurrent pregnancy loss (RPL) is defined as two or more first trimester pregnancy losses, either biochemical (positive blood pregnancy test), or clinical (pregnancy is lost after it is seen on ultrasound).
A single miscarriage is not uncommon, occurring in about 1 in 6 initial pregnancies. 1 in 50 couples with infertility, however, experience recurrent miscarriage. In general, miscarriage becomes more common with age.
There are many possible causes of miscarriage, ranging from anatomic and chromosomal to immunologic and hormonal.
Anatomic refers to structural problems involving the uterus that may cause miscarriage. These problems interfere with the ability of the pregnancy to grow normally in the first trimester. They also may cause problems later in pregnancy and play a factor in pre-term birth or abnormal presentation of the baby at the time of delivery. Anatomic problems may be either congenital (present at birth) or acquired.
Congenital problems with the uterus are of three types.
With a uterine septum, the uterus has a wedge of extra tissue (septum) hanging from the top that functionally divides the uterus into two cavities.
With a bicornuate uterus, the uterus appears to be heart-shaped and has two conjoined cavities instead of the normal single cavity.
And with uterus didelphys, the uterus is present as a paired organ that is essentially a double uterus with two separate cervices, and possibly a double vagina as well.
Acquired problems include endometrial polyps, fibroids, and intrauterine scar tissue. See also: Female Infertility
Another condition, often responsible for second trimester pregnancy loss, is an incompetent cervix, where the cervical muscle is weakened and cannot remain closed as the developing fetus grows and puts pressure on the cervical opening.
Chromosomal refers to genetic problems resulting in an abnormality of the developing fetus, a major cause of miscarriage.
Either partner or even both may be genetically predisposed to passing on an abnormality to the fetus. One study reports that 50-60% of all miscarriages in the first three months of pregnancy are due to chromosomal abnormalities.
There are three types of chromosomal abnormalities:
Abnormal karyotype in the parents occurs in 2% to 5% of cases of RPL. Karyotype is the number and visual appearance of the chromosomes in the cell nuclei of an organism or species.
There may be increased fragmentation of the sperm.
A random abnormality, usually egg error, is associated with advanced maternal age.
Immunologic refers to an imbalance in the way a mother’s immune system is altered during pregnancy so that the fetus is not rejected by her body and is allowed to grow.
Autoimmune factors are the cause of an improper imbalance, known as antiphospholipid antibody syndrome (APS). Blood tests are used to detect the presence of these antibodies, and if present, medication that helps thin the blood may be used.
Hormonal refers to abnormal hormone levels that can affect the uterine lining where the fertilized egg risks not having the best environment for implantation and nourishment.
Women with thyroid and adrenal gland problems and women with diabetes are usually at a higher risk for miscarriage due to hormonal imbalances.
An elevated prolactin level can also disrupt normal uterine lining development.
We recommend testing be carried out after two or more pregnancy losses. The more information we can obtain about the reason for the miscarriage, the more closely we can tailor our treatment and improve your odds of a successful pregnancy.
Clinical review
We’ll make sure we understand your history, and review details of prior losses including any evaluation of karyotype of fetal tissue.
Tests according to causes
Anatomic tests may include ultrasound, HSG, and hysteroscopy.
Chromosomal tests may include examination of fetal tissue (karyotype), parental karyotypes, and sperm DNA fragmentation.
Immunologic tests may include blood tests for lupus anticoagulant, anticardiolipin antibody, and beta2 glycoprotein. Abnormal tests results require retesting in 3 months and similar results to confirm the diagnosis.
Hormonal tests may include thyroid, progesterone and Vitamin D.
Blood clotting disorder
If you have a blood clotting disorder, you should not be tested in relation to pregnancy loss. The American College of Obstetrics and Gynecology has stated that these disorders are not associated with first trimester loss.