Miscarriage is the spontaneous loss of a pregnancy before the 20th week of gestation. While it is natural to worry about personal risk if your mother experienced a miscarriage, the vast majority of these losses are sporadic events that are not inherited. Between 10% and 20% of all known pregnancies end in miscarriage, making it a common experience. Most miscarriages are due to random biological errors unrelated to maternal inheritance.
Statistical Likelihood and Primary Causes
The most frequent cause of an early miscarriage is a random error in the developing fetus’s chromosomes. Approximately 50% of first-trimester miscarriages result from the fetus having an abnormal number of chromosomes, known as aneuploidy. This occurs when the egg or sperm contains too few or too many chromosomes, or when an error happens during early cell division. These events are biological accidents and are not passed down from parent to child.
The high frequency of these non-recurrent chromosomal abnormalities means a single miscarriage in your mother’s history does not automatically mean you share the same risk. The risk of miscarriage for someone who has never had one is around 15% of clinically recognized pregnancies. This risk is only slightly elevated to about 25% after one previous loss, illustrating that miscarriage is often a one-time event. Recurrent pregnancy loss, defined as two or more consecutive losses, affects only 1% to 2% of women, and this smaller group is where inherited factors are investigated.
Inheritable Risk Factors and Genetic Links
Although most miscarriages are not inherited, specific genetic conditions can be passed down, increasing the risk of recurrent loss. One category involves parental chromosomal issues, where a parent carries a “balanced translocation.” In this scenario, segments of two different chromosomes have swapped places, but the parent remains healthy because no genetic material is missing. However, when this parent produces an egg or sperm, the chromosomes may be passed on in an unbalanced way, resulting in a fetus with missing or extra genetic material incompatible with life, causing a miscarriage.
Another inheritable risk factor involves certain medical conditions, such as specific thrombophilias, which are disorders that increase the tendency for blood clotting. Mutations like Factor V Leiden or prothrombin gene mutations are examples linked to an increased risk of recurrent pregnancy loss. These clotting disorders can potentially disrupt the blood flow to the developing placenta. Uterine structural abnormalities, such as a bicornuate or septate uterus, can also have a genetic component, interfering with implantation and growth.
Personal Health Factors You Can Control
Focusing solely on your mother’s history overlooks the significant role of your own health and current lifestyle, which are the most common controllable factors. Maternal age is a major driver of miscarriage risk, as the quality of eggs declines over time. For instance, the risk increases from around 10% for those under 35 to approximately 45% for those over 40.
Uncontrolled chronic health conditions are another concern, including poorly managed diabetes or thyroid disease. High blood sugar levels or untreated thyroid dysfunction can create an environment that is not supportive of a healthy pregnancy. Maintaining a body mass index (BMI) outside of the healthy range—either underweight or overweight—has also been linked to a higher risk. Lifestyle choices like smoking, excessive caffeine intake (over 200 milligrams per day), and heavy alcohol use are all associated with elevated risk.
When to Seek Preconception Genetic Counseling
If you have concerns about your family’s history, a consultation with a healthcare provider or genetic counselor before conception can be informative. These experts will take a detailed family medical history to identify patterns of inherited disease or recurrent pregnancy loss. A strong indicator for seeking counseling is a known family history of recurrent pregnancy loss, defined as two or more consecutive losses.
Preconception testing may be recommended if a genetic link is suspected, often involving a blood test called karyotyping for both prospective parents. This test analyzes the structure of the chromosomes to check for balanced translocations. Blood tests for inherited thrombophilias, or clotting disorders, may also be included in the workup for couples with a history of recurrent loss. This proactive approach helps to identify and manage any underlying genetic or medical issues before a future pregnancy begins.