When experiencing a miscarriage, many expectant mothers feel guilt, anxiety, or even lose faith in pregnancy. However, natural miscarriage is not uncommon and most cases have signs that can be traced. This article introduces 6 common miscarriage symptoms and causes, explains how to differentiate implantation bleeding from various types of abnormal bleeding, and further covers the criteria for diagnosing recurrent miscarriage as well as high-risk groups, to help you better prepare for your next pregnancy.
What is miscarriage? What are the symptoms?
Definition of Miscarriage
Miscarriage generally refers to spontaneous miscarriage, meaning that the fetus stops developing and is expelled from the uterus before the completion of 20 weeks of pregnancy, also commonly “second trimester miscarriages”.
Spontaneous miscarriage is actually not uncommon. Statistics show that up to 31% of pregnancies end in spontaneous miscarriage before the 12th week, with many women experiencing this without ever realizing it. The vast majority of miscarriages occur in the first trimester, i.e., before 12 weeks of pregnancy, accounting for over 80% of all miscarriages. Miscarriages occurring between weeks 12 and 20, referred to as "second-trimester miscarriage," are relatively less common, typically occurring in fewer than 1% of pregnancies. Generally speaking, after the 16th week of pregnancy, placental function becomes more stable and fetal organ development becomes more complete, significantly lowering the risk of miscarriage.
Common Symptoms of Miscarriage
Recognizing common miscarriage symptoms can help expectant mothers detect abnormalities early, allowing them to seek timely medical care, stabilize the fetal condition, and reduce the risk of miscarriage. Below are 5 common symptoms:
1. Vaginal Bleeding
This is one of the most easily noticeable symptoms. The amount of bleeding during a miscarriage varies widely and is particularly related to the gestational age, often accompanied by the passage of blood clots or tissue. If the amount of bleeding increases, or the color changes from brown or pink to bright red, or clots are present, it is recommended to seek medical evaluation as soon as possible.
2. Lower Abdominal Pain or Cramping
Miscarriage-related pain typically presents as crampy, similar to the sensation of uterine contractions during menstruation, especially during the expulsion of pregnancy tissue, and can range from mild to severe. Uterine contractions may cause a dull ache in the lower abdomen or pelvis. If the pain persists or gradually worsens, especially when accompanied by bleeding, increased vigilance is warranted.
3. Sudden Disappearance of Pregnancy Symptoms
Common pregnancy symptoms such as nausea, vomiting, and breast tenderness that suddenly weaken or even completely disappear within a short period of time are not necessarily abnormal; however, it is still recommended to schedule an early follow-up visit with an ultrasound to confirm whether fetal development remains stable.
4. Passing Tissue or Clots
If blood clots along with grayish-white, pink, or red tissue-like material are passed vaginally, this may indicate embryonic or gestational sac tissue. In this case, it is recommended to carefully preserve the expelled tissue and bring it to a physician for examination, to help determine whether a miscarriage has occurred and enable early management.
5. Cervical Shortening or Dilation
If a prenatal ultrasound reveals a shortened or dilating cervix, this may indicate that a miscarriage is occurring. Further evaluation by a physician is needed to determine whether this represents an inevitable or incomplete miscarriage.
Implantation Bleeding or Miscarriage? 3 Key Points to Help You Tell the Difference
"I'm experiencing bleeding in early pregnancy — is it implantation bleeding or a miscarriage?" This is one of the most common concerns for expectant mothers. In fact, light spotting during this period is not uncommon and is often a normal part of the implantation process. If bleeding occurs, you can observe the following 3 key points to help you initially assess whether increased vigilance is needed, and whether you should consider seeking medical confirmation as soon as possible.
1. Timing of the Bleeding
Implantation bleeding usually occurs 6 to 12 days after ovulation, roughly a week before your period is expected. When the fertilized egg implants into the uterine lining, it may irritate small blood vessels, causing light bleeding. Some may mistake this for an early period, but it is typically just part of the implantation process.
However, if bleeding suddenly appears after pregnancy has progressed to weeks 6 through 12, this warrants particular attention, as it may be related to miscarriage or other abnormalities.
2. Color and Amount of Bleeding
The amount of implantation bleeding is usually minimal — it may present as spotting or streaks of blood, with a pale pink or light brown color. This type of bleeding typically resolves within one to two days and does not cause noticeable discomfort. However, if the blood is bright red or dark red in color and increases in volume, approaching or even exceeding a normal menstrual flow, this warrants increased vigilance — especially if the bleeding lasts more than three days, or if blood clots or tissue-like material are passed, as these may well be signs of miscarriage. In such cases, immediate medical evaluation is recommended.
3. Abdominal Pain or Other Symptoms
Implantation bleeding generally does not come with abdominal pain, and even when it does, it is usually just mild discomfort or bloating that does not significantly interfere with daily activities. However, particular caution is warranted if the bleeding is accompanied by other unusual symptoms, especially the following:
- Severe lower abdominal cramping or spasms
- Persistent lower back pain
- Noticeable uterine contractions
- Weakening of pregnancy symptoms
6 Common Causes of Natural Miscarriage
Miscarriage is one of the greatest concerns for many expectant mothers. According to the Mayo Clinic, over half of natural miscarriages are associated with chromosomal abnormalities, which are difficult to prevent. However, some miscarriages are influenced by maternal health, lifestyle habits, or external factors, and understanding these in advance along with regular prenatal check-ups may help reduce the risk of miscarriage. Below are 6 common causes of miscarriage:
1. Chromosomal Abnormalities
The risk of miscarriage increases with maternal age, particularly for pregnant women over 35 years old. This is mainly because older mothers have a higher likelihood of carrying a fetus with chromosomal abnormalities. When there is a problem with the number or structure of chromosomes in the fertilized egg or embryo — such as balanced translocations, abnormal arrangements, or errors during cell division — this may affect normal embryonic development, leading to pregnancy loss. If a woman has experienced multiple miscarriages, her doctor may recommend related testing, such as embryonic chromosome analysis or parental chromosome testing, to help clarify the cause and prepare for a future pregnancy.
2. Uterine Structural Abnormalities
Abnormalities in uterine structure may affect embryo implantation or normal development, thereby increasing miscarriage risk. Common uterine abnormalities include:
- Uterine septum: A dividing membrane within the uterine cavity that disrupts blood flow and hinders implantation
- Fibroids and adenomyosis: May compress the uterine cavity, limiting the space available for embryo development
- Intrauterine adhesions: A condition that tends to occur after multiple uterine surgeries, affecting the integrity of the uterine lining
3. Endocrine Issues
Conditions such as progesterone deficiency, polycystic ovary syndrome (PCOS), hyperprolactinemia, or an overactive or underactive thyroid can destabilize embryo implantation and affect its development, increasing the risk of miscarriage. It is recommended to arrange hormone and thyroid function testing during pregnancy preparation or early pregnancy, so that adjustments can be made to improve pregnancy stability.
4. Infections
Certain bacteria, viruses, or parasites can affect fetal development through the placenta, potentially increasing miscarriage risk. These types of infections often have no noticeable symptoms and can be difficult to detect, which makes screening during pregnancy preparation or early pregnancy especially important, helping to identify issues early and avoid harm to the embryo. More common sources of infection include:
- Chlamydia: A type of sexually transmitted infection
- Toxoplasmosis: May come from undercooked meat or cat feces
- Rubella, Listeria, and other viral or bacterial infections
5. Immune System Abnormalities
In some women, the immune system malfunctions and mistakenly identifies the embryo as foreign, triggering an attack response that impairs embryo implantation or placental function. The most common condition is Antiphospholipid Syndrome (APS), which causes blood clots to form around the embryo, preventing the fetus from properly receiving nutrients and oxygen and increasing the likelihood of miscarriage or abnormal fetal development.
6. Lifestyle Stress and Unhealthy Habits
Excessive stress and unhealthy lifestyle habits can both increase miscarriage risk. Expectant mothers need to pay particular attention to the following 3 points during pregnancy:
- Smoking and excessive alcohol consumption: May impair placental oxygen supply, increasing the risk of abnormal or impaired fetal development
- Staying up late and overexertion: Can easily disrupt endocrine and immune function, making it harder for the body to maintain a stable pregnancy environment
- Chronic stress or significant emotional fluctuations: Elevated levels of stress hormones (such as cortisol) may interfere with embryo implantation and stable development
Signs of an Unhealthy Embryo: How to Identify Risks
An unhealthy embryo most commonly results in fetal arrest (stopped development) or early miscarriage. Sometimes the body doesn't produce an immediate, clear warning sign, and many people only discover during a routine ultrasound that the fetus has stopped growing. 5 key signs to watch out for:
1. Delayed Embryonic Growth, or Size Inconsistent with Gestational Age
If the ultrasound shows the embryo is smaller than expected for its gestational age, or if there is no clear embryonic tissue visible within the gestational sac, it may indicate arrested development. Doctors usually advise monitoring for a few more days before confirming embryo shrinkage.
2. Absence or Weak Fetal Heartbeat
By 6–7 weeks gestation, and no later than 8 weeks, a fetal heartbeat should be detectable by ultrasound. If no heartbeat is detected past this point, or if a previously detected heartbeat is later lost, this may indicate embryonic demise, and the doctor will assess whether further observation or intervention is needed based on gestational age and other findings.
3. Abnormal Changes in hCG Levels
hCG is a key marker for confirming pregnancy. Under normal circumstances, it rises steadily throughout early pregnancy. A slow rise, sudden plateau, or unexpected decline in hCG levels may indicate unstable implantation, or that development has already stopped.
4. Abnormal Discharge After Implantation
Watch out for early pregnancy discharge that is brown or red, especially if accompanied by lower abdominal discomfort, lower back pain, or a sensation resembling the onset of a period.
What Is Recurrent Miscarriage?
Recurrent miscarriage, also known as repeated pregnancy loss, refers to two or more consecutive spontaneous miscarriages before 20 weeks of pregnancy, during the stage when the embryo has not yet stabilized. Common presentations include an observed gestational sac on ultrasound that, after at least two weeks of monitoring, still shows no embryo with a heartbeat, or an embryo that had a detected heartbeat before development subsequently stopped.
Although this may sound concerning, recurrent miscarriage is not an insurmountable problem — in most cases a specific cause can be identified, and with proper diagnosis and treatment, a successful pregnancy is still achievable.
High-Risk Groups for Recurrent Miscarriage
If you fall into any of the following categories, you are considered high-risk for recurrent miscarriage. It is recommended to consult a doctor before trying to conceive to evaluate if further testing or monitoring is needed:
- History of two or more early miscarriages. Risk increases with a history of miscarriage:
- After one miscarriage, miscarriage risk in the next pregnancy slightly increases to 14–21%.
- After two miscarriages, the risk rises to about 24–29%.
- As maternal age increases, the risk of miscarriage does indeed rise, and this applies not only to embryos with chromosomal abnormalities but also to chromosomally normal embryos, whose miscarriage rate likewise increases.
- Acquired or congenital uterine abnormalities account for 10 to 50% of recurrent miscarriages, and include congenital uterine malformations, fibroids, adenomyosis, endometrial polyps, and intrauterine adhesions.
- Family history of genetic disorders, immune system diseases, or chromosomal abnormalities.
- Chronic conditions such as hypertension, diabetes, polycystic ovary syndrome (PCOS), thyroid disorders, or hyperprolactinemia.
- Family history of genetic disorders or chromosomal abnormalities. Chromosomal number or structural abnormalities are the most common cause of sporadic early pregnancy loss — across multiple studies, such abnormalities account for at least 50% of miscarriage cases.
What Tests Are Needed for Recurrent Miscarriage? These 4 Tests Help Identify Possible Causes
If you have experienced two or more natural miscarriages, it is recommended to consult a doctor before your next pregnancy to discuss whether further testing is needed, to help clarify potential causes and build confidence for future pregnancies. Below are commonly recommended tests:
1. Chromosomal Testing
Chromosomal structural abnormalities, such as balanced translocations, are a common cause of miscarriage. Even if both partners appear healthy and have no noticeable symptoms, they may still carry these hidden genetic conditions, which can affect normal embryo development and increase miscarriage risk. For couples planning to conceive, doctors usually recommend that both partners undergo chromosomal testing first, analyzing chromosome structure via a blood sample, which helps detect potential risks early and reduce the likelihood of miscarriage.
2. Hysteroscopy / Ultrasound Examination
This type of examination is mainly used to confirm whether the uterine structure is normal — conditions such as a uterine septum, fibroids, or intrauterine adhesions may all affect embryo implantation or stable development. Hysteroscopy allows direct observation of the inside of the uterus, while ultrasound helps assess uterine thickness and the condition of the muscle layer, giving doctors a more comprehensive understanding of whether the uterine environment is suitable for pregnancy preparation.
3. Autoimmune and Coagulation Function Tests
Antiphospholipid antibodies, anticardiolipin antibodies, and antibodies related to systemic lupus erythematosus (SLE) and other autoimmune conditions are key markers that may indicate blood clotting abnormalities that affect placental blood supply. If test results show abnormalities, the doctor may, depending on the situation, recommend low-dose aspirin or anticoagulants to help stabilize the pregnancy.
4. Hormone and Thyroid Function Tests
Whether the endocrine system is stable affects whether the embryo can successfully implant and continue developing. Below are 4 key indicators recommended for testing:
- Progesterone: Helps maintain early pregnancy and supports stable embryo implantation and development.
- Prolactin: If levels are too high, this may interfere with ovulation or embryo implantation.
- Thyroid function: Thyroid hormone levels that are too high or too low may destabilize pregnancy.
- Ovarian function: Assesses ovarian reserve status and fertility potential, which is also important for pregnancy planning.
How Can IVF Effectively Reduce the Risk of Recurrent Miscarriage?
For women who have experienced multiple miscarriages, the underlying causes of recurrent miscarriage can often be a source of confusion and frustration. Among all known causes, chromosomal abnormalities are among the most common, especially in the early, unstable stage of embryo development. However, with advances in reproductive medicine, IVF combined with preimplantation genetic testing for aneuploidy (PGT-A) can identify chromosomally normal embryos with higher developmental potential before transfer, significantly reducing the risk of miscarriage.
Interested in IVF? Book a Consultation with TFC Taipei Reproductive Center
Led by Dr. Chii-Ruey Tzeng, known as the "Father of Taiwan's IVF," TFC Taipei Reproductive Center has over 40 years of expertise in reproductive medicine**, and has received the prestigious ASRM Star Award six times**, reflecting internationally recognized professionalism. The TFC team of physicians has an average of over 20 years of experience, bringing extensive clinical expertise. TFC's IVF success rate approaches 70%, and it is the only fertility clinic in Taiwan awarded the SNQ National Quality Mark.
TFC features a high-grade cleanroom positive-pressure laboratory, paired with advanced embryo culture technology, including a Time-Lapse imaging system and AI -assisted embryo selection, to continuously monitor embryo development without disturbance, creating a stable and safe culture environment. A team of senior embryologists, combined with systematic analysis, helps physicians select embryos with greater potential, improving implantation stability and pregnancy success rates.
In addition, TFC offers Traditional Chinese Medicine (TCM), psychological counseling, and nutrition clinics, which can be arranged individually based on personal needs — from constitutional conditioning and emotional support to dietary optimization, creating a more holistic mind-body state suited to pregnancy, both inside and out, for a more stable and reassuring treatment journey. If you are trying to conceive, or facing the challenges of recurrent miscarriage, we welcome you to consult TFC Taipei Reproductive Center, where our professional team can help you find renewed confidence and hope.
