Which pregnant women are prone to early birth?

Pregnant women may occasionally experience some adverse reactions in the late stages of pregnancy. They should take good care of their bodies and relax themselves. If there are any signs of premature birth, they should go to the hospital in time to wait for delivery and stop walking around. This is especially important for patients who already suffer from vaginal bleeding or infectious diseases, as they are more likely to give birth prematurely.

1. Those with a history of previous premature birth and/or late miscarriage: The risk of recurrent premature birth in pregnant women with a history of premature birth is 6 to 8 times that of pregnant women without a history of premature birth.

2. History of cervical surgery and cervical insufficiency: Those with a history of cervical conization, LEEP, repeated artificial abortions, dilated cervix, uterine malformations, etc. have an increased risk of premature birth. Pregnant women with cervical insufficiency or cervical length <30mm during 14-28 weeks of pregnancy have an increased rate of premature birth and late miscarriage.

3. In multiple pregnancies, the premature birth rate is generally 50% for twin pregnancies and 75% for triplets.

4. Inflammation of the reproductive tract, such as bacterial vaginosis, Trichomonas vaginitis, chlamydia infection, gonorrhea, syphilis, etc.

5. Urinary tract infection, asymptomatic bacteriuria.

6. Systemic infectious diseases.

7. Vaginal bleeding.

8. Too much/too little amniotic fluid.

9. Those who become pregnant after receiving assisted reproductive technology.

10. Pregnant women have complications, such as hypertension, diabetes, thyroid disease, asthma, etc.

11. People with bad habits such as smoking, drinking or taking drugs.

12. Pregnant women <18 years or >35 years.

13. Body mass index < 19, poor nutritional status, and standing time > 40 h/week.

14. Regular uterine contractions occur repeatedly, such as ≥ 4 times/h.

15. During the 22-34th week of pregnancy, the fetal fibronectin (fFN) is positive in the posterior vaginal fornix secretions.

16. Other factors: such as lack of routine prenatal care, floating population, etc.

There are four main causes of premature birth: (1) Inflammation, which often occurs before 32 weeks (40%); (2) Decidua basalis bleeding (placental abruption) (40%): it can occur at any gestational age; (3) Over-distension of the uterus, cervical insufficiency (10%) (twins, polyhydramnios, uterine malformations, etc.); (4) Endocrine changes leading to premature labor: it often occurs after 32 weeks (25%), prematurely activating the fetal hypothalamic-pituitary-adrenal system.

Pathogenesis

Clinical studies have confirmed that more than 90% of premature births between 24 and 28 weeks are related to infection, 80% of premature births before 30 weeks are due to infection, and only 15% of premature births between 34 and 36 weeks are due to infection. There are four main routes of intrauterine infection: ① ascending infection from the lower reproductive tract; ② spread through the placenta via hematogenous transmission; ③ retrograde spread from the abdominal cavity through the fallopian tube; ④ invasive procedures, such as amniocentesis, percutaneous fetal blood sampling, chorionic villus sampling, and umbilical cord blood puncture.

Among them, ascending infection through the vagina and cervix is ​​the main route. The pathogens are mainly bacteria, most of which originate from the vagina. The main pathogens are: Group B Streptococcus, Escherichia coli, Ureaplasma, Bacteroides, Gardnerella vaginalis, Fusobacterium, and Mycoplasma hominis. Most of them are conditional pathogens with relatively low virulence, and viral infections are rare.