Women’s Health | IVANA MD | Missouri City, TX
Experiencing a miscarriage is one of the most emotionally painful events a woman can go through. Yet despite how common it is, many women are left without clear answers about why it happened. Understanding the medical causes of miscarriage does not take away the grief, but it can provide clarity, reduce self-blame, and open the door to better care in future pregnancies.
How Common Is Miscarriage?
Miscarriage, medically known as spontaneous abortion, is the most common complication of early pregnancy. The American College of Obstetricians and Gynecologists estimates that 10 to 25 percent of all clinically recognized pregnancies end in miscarriage, and the actual number is likely higher when accounting for very early losses that occur before a pregnancy is confirmed. The majority of miscarriages occur in the first trimester, before 13 weeks of pregnancy.
What Causes Miscarriage?
Chromosomal Abnormalities
The single most common cause of miscarriage is a chromosomal abnormality in the embryo. Research published in the New England Journal of Medicine found that chromosomal issues account for approximately 50 to 60 percent of all first trimester miscarriages. These abnormalities occur randomly during fertilization or early cell division and are not caused by anything the mother did or did not do. The most common chromosomal errors include trisomy, monosomy, and triploidy, all of which result in an embryo that cannot develop normally.
Hormonal Imbalances
Hormones play a critical role in establishing and maintaining a pregnancy. Insufficient progesterone during the luteal phase, a condition known as luteal phase defect, can prevent the uterine lining from adequately supporting an implanted embryo. Thyroid disorders, both hypothyroidism and hyperthyroidism, have also been strongly linked to miscarriage risk. A study in Thyroid journal found that even subclinical hypothyroidism, where thyroid levels are only mildly abnormal, significantly increases the risk of pregnancy loss.
Uterine Abnormalities
Structural problems with the uterus can interfere with implantation or fetal development. Conditions that increase miscarriage risk include:
- A uterine septum, which divides the uterine cavity and reduces blood supply to the embryo
- Uterine fibroids, particularly those that distort the uterine cavity
- Asherman syndrome, where scar tissue inside the uterus prevents normal implantation
- A bicornuate or other irregularly shaped uterus
Immune System Disorders
The immune system plays a complex role in pregnancy. In some women the immune system mistakenly attacks the developing pregnancy. Antiphospholipid syndrome, an autoimmune condition that causes abnormal blood clotting, is one of the most well-established immune causes of recurrent miscarriage. Research published in the American Journal of Obstetrics and Gynecology found that antiphospholipid syndrome accounts for approximately 15 percent of recurrent pregnancy losses and is highly treatable with blood thinners during pregnancy.
Infections
Certain infections during pregnancy can increase the risk of miscarriage, including:
- Bacterial vaginosis, which has been linked to second trimester pregnancy loss
- Listeria, toxoplasmosis, and rubella
- Sexually transmitted infections including chlamydia and gonorrhea
- Uncontrolled urinary tract infections
Advanced Maternal Age
Age is one of the most significant risk factors for miscarriage. As women age, egg quality declines and the likelihood of chromosomal errors during fertilization increases. Research published in the British Medical Journal found that miscarriage rates rise sharply with age, from approximately 9 percent in women aged 20 to 24 to over 75 percent in women aged 45 and older. This is primarily driven by the increased rate of chromosomal abnormalities in older eggs.
Lifestyle and Environmental Factors
While most miscarriages are caused by factors outside a woman’s control, certain lifestyle factors have been associated with increased risk, including:
- Smoking, which reduces blood flow to the placenta and is linked to higher miscarriage rates
- Heavy alcohol consumption
- High caffeine intake above 200mg per day according to research in the British Medical Journal
- Exposure to environmental toxins including pesticides and certain chemicals
- Uncontrolled chronic conditions such as diabetes or high blood pressure
What Does Not Cause Miscarriage
It is equally important to address what does not cause miscarriage, because many women carry unnecessary guilt after a loss. Normal physical activity, sexual intercourse, stress, most medications taken before pregnancy was known, a fall or minor accident, and morning sickness do not cause miscarriage. The vast majority of pregnancy losses are the result of genetic or biological factors that are entirely beyond anyone’s control.
Recurrent Miscarriage
Recurrent miscarriage, defined as two or more consecutive pregnancy losses, affects approximately 1 to 2 percent of couples trying to conceive according to the American Society for Reproductive Medicine. Women who experience recurrent miscarriage should be evaluated for chromosomal abnormalities in both partners, uterine structural issues, hormonal disorders, immune system conditions, and clotting disorders. In many cases a treatable cause is identified.
When to See a Doctor
You should speak with a women’s health provider after any miscarriage to discuss what may have caused the loss and whether any testing is recommended. After two or more miscarriages a thorough recurrent pregnancy loss evaluation is strongly advised. Early answers lead to better outcomes in future pregnancies.
A miscarriage is not your fault. It is a medical event, and with the right care and evaluation, many women go on to have successful pregnancies.
📍 Schedule your women’s health appointment with IVANA MD in Missouri City, TX.
📞 346-585-4077.
4220 Cartwright Road, Suite 201, Missouri City, Texas 77459.
References
American College of Obstetricians and Gynecologists. (2018). Early Pregnancy Loss. Obstetrics & Gynecology, 132(5), https://www.acog.org/clinical/clinical-guidance/practice-bulletin/articles/2018/11/early-pregnancy-loss
Santos, T. S., Ieque, A. L., Carvalho, H. C., Sell, A. M., Lonardoni, M. V. C., Demarchi, I. G., Lima Neto, Q. A., & Teixeira, J. J. V. (2017). Antiphospholipid syndrome and recurrent miscarriage: A systematic review and meta-analysis. Journal of Reproductive Immunology, 123, 78–87. https://pubmed.ncbi.nlm.nih.gov/28985591/
Nybo Andersen, A. M., Wohlfahrt, J., Christens, P., et al. (2000). Maternal age and fetal loss: population based register linkage study. British Medical Journal, 320(7251), 1708–1712.https://www.bmj.com/content/320/7251/1708
Wilcox, A. J., Weinberg, C. R., O’Connor, J. F., et al. (1988). Incidence of early loss of pregnancy. New England Journal of Medicine, 319(4), 189–194.https://pubmed.ncbi.nlm.nih.gov/3393170/
