Pregnancy Loss Causes and Risk Factors Reasons for Miscarriage Why First-Trimester Miscarriages Happen By Krissi Danielsson Krissi Danielsson, MD is a doctor of family medicine and an advocate for those who have experienced miscarriage. Learn about our editorial process Krissi Danielsson Medically reviewed by Medically reviewed by Meredith Shur, MD on April 20, 2020 Meredith Shur, MD, FACOG, is board-certified in obstetrics and gynecology, as well as a certified medical examiner. Learn about our Review Board Meredith Shur, MD on April 20, 2020 Print Reasons for miscarriage. JGI/Tom Grill / Getty Images The reasons for miscarriage aren't always known. In fact, more often than not, you will simply not know what caused a specific miscarriage. The following are some possible explanations for why a single first-trimester miscarriage might occur in someone without a history of miscarriage. (Causes of recurrent miscarriages are more complex.) Chromosomal Abnormalities in the Baby Certain errors in the chromosomes of the developing baby are incompatible with life and lead to miscarriage. This is suspected to be the explanation behind the vast majority of first-trimester miscarriages, especially in women without a history of miscarriage. According to the American College of Obstetricians and Gynecologists, this is due to the embryo having an abnormal number of chromosomes. Moms over 35 are probably more likely to miscarry for this reason. Most women who have pregnancies affected by chromosomal abnormalities will have normal subsequent pregnancies. Why Chromosomal Abnormalities Can Cause Miscarriage Infections or Food Poisoning Some types of viral and bacterial infections can lead to miscarriage or stillbirth. Infections generally pose a higher risk of pregnancy loss in the second trimester and later, but a few can cause problems in the first trimester also. Bacterial and Viral Infections and Miscarriage No Known Reason Sometimes even when the doctor tests for chromosomal abnormalities in the lost pregnancy, the results come back normal. It can be very hard to cope with having no answer for why a miscarriage occurred, and you may be tempted to blame yourself. But miscarriage is almost never anyone's fault. Underlying Health Problems Sometimes underlying chronic health conditions, such as diabetes or celiac disease, in the mother can lead to an unexpected miscarriage. Most of the time, however, detecting and treating that condition should lead to a normal subsequent pregnancy. Other times, multiple miscarriages may occur because of antiphospholipid syndrome or another known recurrent miscarriage cause. Antiphospholipid Antibody Syndrome Was this page helpful? Thanks for your feedback! Get diet and wellness tips delivered to your inbox. Sign Up You're in! Thank you, {{form.email}}, for signing up. There was an error. Please try again. What are your concerns? Other Inaccurate Hard to Understand Submit Article Sources Verywell Family uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. American Pregnancy Association. Miscarriage. Updated October 10, 2019. American College of Obstetricians and Gynecologists. Early Pregnancy Loss. Updated August 2015. Hardy K, Hardy PJ. 1(st) trimester miscarriage: four decades of study. Transl Pediatr. 2015;4(2):189–200. doi:10.3978/j.issn.2224-4336.2015.03.05 Tersigni C, Castellani R, Waure CD, et al. Celiac disease and reproductive disorders: meta-analysis of epidemiologic associations and potential pathogenic mechanisms. Human Reproduction Update. 2014;20(4):582-593. doi:10.1093/humupd/dmu007. Di Prima FA, Valenti O, Hyseni E, et al. Antiphospholipid Syndrome during pregnancy: the state of the art. J Prenat Med. 2011;5(2):41–53.