Patient's question:
Medical history: At 3 months of pregnancy, an ultrasound revealed fetal demise. Dilation and curettage (D&C) was performed.Doctor's answer:
The causes of miscarriage include:(1) Embryonic (or fetal) factors:
1. Abnormal embryonic development is the most common cause of early miscarriage, accounting for approximately 50–60% of cases due to chromosomal abnormalities.
2. Placental abnormalities, such as inadequate trophoblast development, villous degeneration, or low placental attachment, can disrupt fetal-placental circulation, leading to miscarriage.
(2) Maternal factors:
1. Acute infections may cause fetal death due to pathogens or toxins invading the placenta, or lead to miscarriage due to high fever or poisoning-induced uterine contractions.
2. Severe anemia or heart failure may cause fetal hypoxia and death.
3. Endocrine disorders, such as luteal insufficiency, can impair decidua development, affecting embryo growth.
4. Uterine malformation, fibroids, or abnormalities may hinder embryonic development.
5. Sometimes, cervical incompetence (relaxation of the internal os) may fail to withstand the pressure of the growing fetal sac, resulting in late miscarriage.
6. Severe emotional stress, trauma, or sexual intercourse may also cause miscarriage, but these are often contributing factors, with the primary cause typically being embryonic defects.
(3) External factors: Toxic substances that can lead to miscarriage include cadmium, lead, organic mercury, DDT, and other radioactive materials. These toxins may directly affect fetal somatic cells or indirectly influence the fetus through the placenta, causing miscarriage.
(4) Immunological factors: Maternal rejection of the fetus due to immune incompatibility between the mother and fetus may lead to miscarriage. Identified immunological factors include:
- Spousal histocompatibility antigens
- Fetal antigens
- Blood group antigens
- Maternal cellular immune regulatory imbalance
- Lack of maternal (blocking antibodies) during pregnancy
- Deficiency of maternal cytotoxic antibodies against paternal lymphocytes
(5) Maternal-fetal blood type incompatibility: Blood type incompatibility between the mother and fetus often causes late miscarriage, such as ABO and Rh blood type mismatches.
It is recommended to:
- Test endocrine levels and anti-embryonic antibodies using electrochemical luminescence on days 3–5 of the menstrual cycle.
- Perform vaginal examination on days 3–5 after menstruation.
- Undergo dynamic digital hysterosalpingography and 4D vaginal ultrasound.