Threatened Prematurity

Introduction Premature birth: In the mid-late pregnancy, sensitive pregnant women can feel uterine contractions. This kind of unfixed intermittent time and irregular duration of contractions are not the contractions of the uterus, but the physiological manifestations of the uterus. Braxton-Hick's contractions. If the uterine contraction intermittent time is within 10 min, there is a tendency to gradually shorten, the contraction duration is 20 to 30 s, and there is a tendency to gradually prolong, which can be considered as a manifestation of threatened preterm labor. Sometimes accompanied by vaginal discharge, cervical dilatation or premature rupture of membranes.

Cause

About 30% of preterm births have no obvious cause. Common incentives are:

1. Pregnant women:

(1) excessive expansion of the uterus: twin or multiple pregnancies, too much amniotic fluid can make the intrauterine pressure high, early delivery and premature birth.

(2) Cervical stenosis: In anatomy, there is no true sphincter-like arrangement in the uterine neck. The connective tissue is mainly composed of collagen fibers, which is elastic and has a sphincter-like effect on the cervix. In the second trimester, the uterine isthmus extends to form the lower uterus. The internal cervix is relaxed and the amniotic cavity pressure is gradually increased. The cervix is passively dilated. The amniotic sac bulges toward the neck tube. The membrane is broken due to tension changes or infection factors. Premature rupture of premature rupture of membranes.

(3) combined with acute or chronic diseases: such as viral hepatitis, acute nephritis or pyelonephritis, acute appendicitis, viral pneumonia, high fever, rubella and other acute diseases; heart disease, diabetes, severe anemia, hyperthyroidism, hypertension, Chronic diseases such as asymptomatic bacteriuria.

(4) combined with uterine malformations: (such as double-horned uterus, mediastinal uterus), cervical relaxation, uterine fibroids.

(5) Pregnancy comorbidity: pregnancy with chronic nephritis, pregnancy with heart disease, pregnancy with hepatitis and pregnancy with lupus erythematosus, etc. On the one hand, due to medical complications, the mother can cause systemic ischemia and hypoxia, and the placental perfusion is also insufficient. Inducing premature birth; on the other hand, the severity of the disease poses a danger to the mother and causes iatrogenic preterm birth for the safety of the mother.

(6) Pregnancy complications: placenta previa, early placental stripping, pregnancy-induced hypertension syndrome, intrahepatic cholestasis of pregnancy.

(7) Smoking, drug abuse, alcoholism, severe malnutrition.

(8) Others: such as long-distance travel, climate change, residential plateau, family migration, emotional fluctuations and other mental and physical burdens; direct abdominal impact, trauma, sexual intercourse or surgical stimulation.

2, fetal placenta:

(1) Early placenta and placenta were stripped early.

(2) too much or too little amniotic fluid, multiple pregnancy.

(3) fetal malformation, fetal death, abnormal fetal position.

(4) premature rupture of membranes, chorioamnionitis.

an examination

Related inspection

Obstetric B-ultrasound system fetal ultrasound examination

diagnosis:

Uterine contraction and progression of labor only means that the pregnancy is coming to an end. As for whether it is a premature birth, the key is to determine the gestational age and the size of the fetus. Clinically, the gestational age and estimated fetal size can be estimated from the following aspects:

1. Clinical calculation: Learn more about the previous menstrual cycle, ask about the last menstrual date, the start of early pregnancy reaction and the start time of fetal movement; according to the gynecological examination during early pregnancy, the size of the uterus is consistent with the menstrual month; refer to the current pubic uterus length and The abdominal circumference is calculated as the gestational age.

2. The cervical map predicts preterm birth according to the length of the cervix and the size of the cervix. There are two ways:

(1) Finger test: including anal examination and vaginal examination, foreign vaginal examination is more. At 25 to 31 weeks of gestation, the length of the cervical canal was found to be 1 cm; when the opening of the cervix was able to accommodate the fingertips (1 cm), premature birth often occurred several weeks later.

(2) B-ultrasound: If B-ultrasound is found: 1 cervix retraction, the internal mouth to the outer neck tube is 1cm long; 3 fetal membrane bulges into the neck tube (ie, the anterior amniotic sac is prominent); 4 lower uterus thinning.

3, ultrasound examination: fetal head diameter, head circumference, abdominal circumference, femur length and gestational age and weight are closely related. The gestational age and fetal size can be estimated from the ultrasound measurements. The measurement of double top diameter is more accurate and less error, such as 85mm, 96% fetal weight 2500g; the reliability of femur length measurement is about 90%, such as 6.8cm, fetal weight 2500g.

Differential diagnosis

When the pregnancy enters the late stage, the sensitivity and contractility of the uterus gradually increase, and the contraction often occurs after exertion and fatigue. However, the rest is short-lived, which is different from the clinical manifestations of threatened preterm labor. As for the inevitable premature birth, it needs to be differentiated from the fake array. The characteristic of false contraction is that the contraction interval is long and irregular, the duration is short and not constant, and the contraction strength does not increase, often appearing at night and disappearing in the early morning. This contraction only causes slight pain in the lower abdomen, the length of the cervical canal is not shortened, and the cervix is not significantly dilated, which can be inhibited by sedatives.

The material in this site is intended to be of general informational use and is not intended to constitute medical advice, probable diagnosis, or recommended treatments.