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Repeated miscarriage, also called spontaneous or habitual abortion, is defined as three or more pregnancy losses in a row before 20 weeks or with a fetal weight of less than 500 grams by the American College of Obstetricians and Gynecologists (ACOG). (See Infertility Awareness November 2007). This occurs in approximately 3-5% of women trying to conceive. The causes of recurrent miscarriages are varied and sometimes controversial; often there is more than one cause. In approximately 50% of women who have repeated pregnancy losses no cause can be identified after a thorough evaluation. The age of the fetus at the time of the loss can sometimes give a physician clues as to the cause. For example, research suggests that 70% of losses that occur in the first 12 weeks (trimester) are due to chromosomal problems while losses occurring after that time may be due to problems with the cervix, a condition known as an incompetent cervix, or other causes. Genetic or Chromosomal Causes  The most common inherited chromosomal cause is a translocation which occur s when one chromosome is attached to another. The parent who carries the translocation is often normal but the genetic material they pass on to their offspring may not be, resulting in too much or too little of the genetic material. Because the developing embryo is abnormal in most cases a miscarriage results because the fetus would not have survived. Chromosomal anomalies or abnormalities occur more often by chance however, resulting in a missing chromosome or extra chromosomes. For example, Down’s syndrome (also known as Trisomy 21) is a chromosomal anomaly that has an extra copy of chromosome 21. Diagnosis of chromosomal anomalies may be made by doing a blood test called karyotyping on the parents. This test may also be done on the products of conception when possible and if the physician thinks it will shed some light on the problem and help with future pregnancies. Age increases the likelihood of miscarriage due to chromosomal causes. It is estimated that at least a third of pregnancies in women over the age of 40 will miscarry due to chromosomal abnormalities.
The inside of the uterine cavity may be severely scarred making it difficult for an embryo to implant properly or interfering with the placental attachment to the uterine wall. This condition is known as Asherman’s syndrome. The cavity may be distorted by fibroid tumors or contain polyps. Finally, a condition known as incompetent cervix which causes the cervix to open too soon can induce miscarriage later on in pregnancy. Diagnosis of a uterine condition may be made by hysterosalpingogram- an X-ray that can visualize the uterus; sono-hysterogram- an ultrasound with a saline solution infusion in the uterus ; or hysteroscopy- a surgical procedure used to visualize the inside of the uterine cavity with a lighted scope. For more information on these procedures visit these websites: http://www.fertilityjourney.com/testinganddiagnosis/testsforwomen/ Medical Conditions
If you have a medical condition that puts you at higher risk for miscarriage it is best to get the condition under control before attempting pregnancy. For example, diabetic women should have their blood sugar under control to improve pregnancy outcomes. Blood Disorders/ Hormonal Imbalances/ Autoimmune Disorders Progesterone is a hormone made by the ovary to prepare the lining of the uterus for the implantation of the embryo. Low levels of progesterone in the luteal phase (the second half of the cycle after ovulation) of the menstrual cycle referred to as a luteal phase defect (LPD), has been associated with recurrent miscarriages but there is no reliable method available to diagnose the condition.  Finally, according to a report by the American Society for Reproductive Medicine (ASRM) there is evidence to suggest that the integrity of the sperm DNA may affect embryo development and possibly increase miscarriage rates. The data is preliminary and at this time it is not known how often these defects contribute to recurrent losses. Treatment Cytogenetic analysis or karyotyping of the miscarried pregnancy can sometimes give your physician useful information for use in future attempts. The test is expensive however and may only be indicated if the physician determines it will influence future treatment. If the cause is genetic in some cases in vitro fertilization (IVF) with Preimplantation Genetic Diagnosis (PGD) (See: http://www.fertilityjourney.com/therapyoptions/ If the problem is in the uterine cavity surgical correction may improve the success rate in future pregnancies. Polyp removal and the correction of a uterine septum typically yield good outcomes in most cases. For patients with clotting disorders anticoagulant therapy with heparin and aspirin can improve the chances of delivering a healthy baby. In conclusion, even if you have experienced recurrent pregnancy losses your chances of having a baby are good. As always when trying to get pregnant maintain a healthy lifestyle by eating right, exercising and avoiding alcohol, tobacco and recreational drug use. Consult with your physician if you have been trying to get pregnant and have been unsuccessful especially if you are over 35. For additional information on this topic visit these websites: American Society for Reproductive Medicine Patient Fact Sheet: Recurrent Pregnancy Loss. Available at: http://www.asrm.org/Patients/FactSheets/recurrent_preg_loss.pdf
References: Poland B, Miller J, Jones D, Trimble BK: Reproductive counseling in patients who have had a spontaneous abortion. Am J Obstet Gynecol 1977 Apr 1; 127(7): 685-91 Quenby S, Farquharson R. Predicting recurring miscarriage-what is important? Obstet Gynaecol 1993; 82: 132-8 Warburton D, Fraser F: Spontaneous abortion risks in man: data from reproductive histories collected in a medical genetics unit. Am J Hum Genet 1964 Mar; 16: 1-25 |