Abortion of the cervix

Termination of pregnancy before 28 weeks of pregnancy or when the fetus weighs less than 1000g is called miscarriage. Miscarriage that occurs before 12 weeks of pregnancy is called early pregnancy miscarriage, and miscarriage that occurs between 12 weeks and less than 28 weeks of pregnancy is called late miscarriage. Miscarriage is divided into spontaneous abortion and induced abortion. The incidence of spontaneous abortion accounts for about 15% of all pregnancies, most of which are miscarriages in the early stages of pregnancy. There are also two types of miscarriage: missed miscarriage and habitual miscarriage.

1. Genetic factors

In the early stages of spontaneous abortion, 50% to 60% of test tube embryos have chromosomal abnormalities, most commonly abnormalities in the number of sex chromosomes, followed by abnormalities in the chromosome structure. Abnormalities in quantity include trisomy, triploidy and single X, and abnormalities in structure include sex chromosome breakage, inversion, absence and substitution. Most test tube embryos with chromosomal abnormalities result in miscarriage. Very few of them may grow into fetuses again, but they may also have some functional abnormalities or malformations after birth. If a miscarriage has occurred, the only material of pregnancy is sometimes an empty gestational sac or a decaying test tube embryo.

2. Environmental factors

There are many external adverse factors that affect reproductive function, which may directly or indirectly harm the test tube embryo or fetus. Excessive exposure to some harmful compounds (such as arsenic, lead, benzene, indoor formaldehyde, chloroprene, butylene oxide, etc.) and physical factors (such as radiation, noise and high temperature, etc.) can cause miscarriage.

3. Pregnant mother factors

(1) Systemic diseases Acute illness during pregnancy and high fever can cause uterine contractions and lead to miscarriage; bacterial toxins or viruses (herpes simplex virus, rubella virus, etc.) enter the fetal blood circulation through the embryo, causing the fetus to die and causing miscarriage. In addition, pregnant women suffering from severe anemia or heart failure can cause fetal hypoxia and may also cause miscarriage. If a pregnant woman suffers from chronic nephritis or hypertension, the fetus may be blocked and cause miscarriage.

(2) Male reproductive organ diseases Pregnant women with uterine malformations (such as didelphys, uterine septum and uterine hypoplasia) and pelvic tumors (such as uterine fibroids) may affect the development of the fetus and cause miscarriage. Relaxation of the internal cervical os or moderate to severe cervical lacerations can easily lead to late-stage miscarriage due to placental abruption.

(3) Endocrine imbalance, hypothyroidism, severe uncontrolled diabetes, and luteal insufficiency can all lead to miscarriage.

(4) Traumatic pregnancy, especially abdominal surgery in early pregnancy or trauma in late pregnancy, can cause uterine contractions and lead to miscarriage.

4. Insufficient endocrine function of the embryo

In the early stages of pregnancy, in addition to the luteinizing hormone in the uterus and ovaries that secretes estrogen, the embryonic trophoblast also slowly produces estrogen. After 8 weeks of pregnancy, the embryo gradually becomes the main site for the production of estrogen. In addition to estrogen, the embryo also produces other growth hormones such as β-chorionic gonadotropin, embryonic lactogen and estrogen. In the early stages of pregnancy, the growth hormone level decreases, and pregnancy cannot be repeated, resulting in miscarriage.

5. Immunity Factors

Pregnancy is like allogeneic transplantation. There is a complex and unique medical immunological relationship between the test tube embryo and the pregnant mother, which makes the test tube embryo non-resistant. If the immune systems of the mother and child are not compatible, the pregnant mother may resist the test tube embryo and cause miscarriage. The relevant immune factors mainly include the father's tissue compatibility antigens, fetal specific antigens, blood type antigens, and maternal cytokine imbalance.