Overview
Induced labor is defined as the termination of pregnancy after 12 weeks of gestation by inducing uterine contractions artificially for either maternal or fetal reasons. Depending on the week of pregnancy at the time of induction of labor, it can be categorized into mid-term induction of labor (14 to 28 weeks) and late-term induction of labor (after 28 weeks).
Preparation for induction of labor
Various factors are involved in the success of induced labor. Cervical ripeness is an important factor in determining the success of induction of labor. If the cervix is not ripe, induction of labor is not always successful. If the cervix is ripe, most of the labor can be delivered vaginally.
1. Cervical score
In 1964, Bishop developed a scoring system to determine the suitability of a pregnant woman for elective induction of labor. The Bishop score is now recognized as a common method of estimating cervical ripeness. He believed that a score of ≥7 indicates cervical ripeness, and the higher the score, the more ripe the cervix is, and the more likely it is to be successful in inducing labor. The higher the score, the more mature the cervix is and the easier it is to induce labor. If the score is below 6, cervical ripening should be promoted.
2. Methods of promoting cervical ripening
The cervix is mainly composed of epithelium, smooth muscle, hoof tissue, glands and stroma. The degree of cervical ripening is not necessarily proportional to the week of gestation, but is related to the biological changes of the cervical tissues. After pregnancy, the cervical tissue undergoes changes, which are evident with the progression of pregnancy and reach a peak during labor and delivery, and are typified by: a marked decrease in collagen fibers and laxity in the form of a meshwork; vascular rage and congestion; leukocyte accumulation attached to the wall, and the presence of large numbers of leukocytes and fibroblasts in the mesenchyme. Cervical ripening may be the result of a variety of techniques, such as estrogen, progesterone, relaxin and prostaglandins.
Methods of inducing labor
The ideal method of inducing cervical ripening is similar to the natural process of ripening, does not cause excessive uterine contractions, does not affect uterine blood flow, and does not jeopardize the safety of the fetus or the mother. There are various methods to promote cervical ripening, and there is no single perfect and highly effective method. At present, the commonly used methods are divided into two categories: non-pharmacological and pharmacological:
1. Non-pharmacological methods
① Artificial membrane stripping (basically not used); ② Artificial rupture of membrane (not effective when used alone); ③ Water bladder or Foley’s urethra (not routinely used); ④ Moisture-absorbing dilatation or Lamicel rod (seldom used); ⑤ Nipple stimulation (not commonly used); ⑥ Needle therapy (basically not used).
2. Pharmacologic therapy
① Hysteronin, a small dose of low concentration intravenous drip; ② prostaglandin PGE2 (routinely used); ③ PGE2 gel intracervical administration (rarely used); ④ PGE2 vaginal controlled-release tablets – probenecid (commonly used); ⑤ Misoprostol (not routinely used); ⑥ vaginal placement of Misoprostol; ⑦ Carbapenem suppository (basically not used); ⑧ Mifepristone (not used for late induction of labor).
Pre-induction examination
The examinations to be done for induced labor are:
1. Detailed inquiry about medical history, including past history, bleeding history, history of liver and kidney diseases, menstrual history, history of pregnancy and childbirth and the passage of this pregnancy.
2. General and gynecological examination and routine leukorrhea test.
3. Measurement of body temperature, pulse, blood pressure, blood and urine tests, liver and kidney function tests, chest X-ray, and electrocardiogram if necessary.
4. Severe cervicitis or excessive secretion should be treated first, and can be performed only after the condition improves; antibiotics should be given before the operation to prevent infection. If necessary, culture of secretion and drug sensitivity test should be done.
5. Those with large gestation, cervical dysplasia, small uterine opening and long cervical canal need to be given certain drugs before operation.
6. Ultrasound for placenta localization if necessary, contraindicated for those with hypoplastic placenta.
Indications, programs and contraindications for inducing labor in the middle stage of pregnancy
Mid-term pregnancy (middle pregnancy) refers to the end of the 14th to 27th week of pregnancy. The fetus is larger in the middle stage of pregnancy, the skeleton has been formed, and the cervix is immature, so it is more difficult to induce labor and prone to serious complications.
1. Induction of labor by water bladder
(1) Indications and contraindications Applicable to: pregnancy in 13 ~ 27 weeks require termination of pregnancy; due to some diseases, it is not suitable to continue pregnancy; no sex within 3 days; body temperature does not exceed 37.5 ℃; no inflammation of the reproductive organs. It can be applied to pregnant women with liver and kidney diseases due to the absence of drug side effects. Water bladder induction of labor is prohibited in the following cases: acute stage of various systemic diseases; acute exacerbation of chronic inflammation, such as vaginitis, severe cervical erosion, pelvic inflammation; repeated vaginal bleeding during pregnancy or ultrasound suggestive of placenta praevia; keloidal uterus; stillbirth or expired miscarriage.
(2) Clinical application After the patient urinates, take the lithotomy position of the bladder, routinely disinfect the towel, dilate the vagina with a vaginal speculum, disinfect the vagina and cervical canal, clamp the anterior lip of the cervix with a cervical forceps and gently pull it outward. The prepared water bladder (No. 16-18 catheter, double-layer condom) was clamped with a long curved forceps and sent into the uterine cavity through the external cervical os, placing it between the uterine wall and the fetal sacs until all the water bladder was placed into the uterine cavity. Strict asepsis was observed during the procedure to avoid contact of the water bladder with the vaginal wall. Then saline at room temperature is injected into the uterine cavity through the catheter, and 300-500 ml of saline is injected into the catheter according to the size of the gestation month. the end of the catheter is tied with a silk thread and wrapped with gauze and then placed in the vagina. Generally 12 to 24 hours after placing the water bladder can cause contractions. Mechanism: the use of mechanical stimulation of pressure to cause contractions, dilate the mouth of the uterus and achieve the purpose of inducing labor. The success rate is about 90%. Although the water bag method of inducing labor is old, but the required instruments are simple, the operation technique is easy to master, the effect is good, no adverse drug reactions. Infection is the most common and dangerous complication of water balloon induction of labor, so antibiotics should be given to prevent infection after surgery. Now most of the clinical joint drug use. It has been reported that small water bladder combined with levano and misoprostol is used to induce labor in middle pregnancy with high success rate, which can shorten the time of fetal expulsion, shorten the time of pain, and reduce the amount of postpartum hemorrhage.
2. Induction of labor with Levano
(1) Indications and contraindications Indications for inducing labor by intra-amniotic injection of Levano: termination of pregnancy at 16-27 weeks; fetal malformation or stillbirth; inappropriate for continuation of pregnancy due to certain diseases such as rheumatic or congenital heart disease, tuberculosis, hypertension, anemia, hyperthyroidism, schizophrenia, temporal lobe epilepsy in the stable stage and advanced tumors, etc.; mild inflammation of the reproductive tract, recurrent vaginal bleeding or recent vaginal bleeding in pregnancy; mild inflammation of the reproductive tract, repeated inflammation of the genital tract, or repeated inflammation of the reproductive tract. vaginal bleeding or a small amount of vaginal bleeding in the recent past, in order to prevent the upward infection, it is not suitable for those who operate vaginally to induce labor, it can be done as intra-amniotic injection of drugs; the body temperature does not exceed 37.5 ℃. It should be noted that it is forbidden in the acute stage of pregnant women suffering from various systemic diseases and liver and kidney diseases.
The indications of levano amniotic cavity induction of labor are basically the same as that of water bag induction of labor, but pregnant women with liver and kidney diseases should not be used. It is mainly used to induce labor at 13 to 15 weeks of pregnancy.
(2) Clinical application Levano is a strong bactericidal agent, with antibacterial effect on a variety of gram-positive and negative bacteria. It can also be used for inducing labor in middle pregnancy. According to the route of application, it can be divided into extra-placental injection method and intra-amniotic injection method. Extra-fetal membrane injection method of operation: pregnant women urinate and take the bladder in the lithotomy position, routine disinfection of the towel, vaginal speculum dilation of the vagina, exposure of the cervix, with iodophor cotton balls to disinfect the vagina and cervical canal, with cervical forceps clamp the anterior lip of the cervix, with a toothless tweezers will be 14 or 16 rubber catheter slowly inserted into the uterine cavity (between the fetal membranes and the uterine wall), up to the depth of the uterine cavity of about 2 / 3, in the event of bleeding, should be changed to send in the direction of the catheter. When the catheter is in place, slowly inject 100mg of Levano solution (diluted with 50ml of water for injection). After the injection, the end of the catheter is folded and tied tightly, wrapped in sterile gauze and placed in the vagina, and the catheter is removed in 24 hours. Mechanism: Levano extra-placental administration, in addition to the drug itself causes contractions, cervical catheter also produces local mechanical stimulation to achieve the role of promoting cervical softening and ripening to promote the expulsion of the fetus placenta.
Amniotic cavity injection method of operation: pregnant women empty the bladder supine on the operating table, the operator for abdominal examination, ask the fetal back and limb position, in the bottom of the uterus and the pubic symphysis between the midline next to the fetal limb side of the 2 transverse fingers as the puncture site. Routine disinfection and spreading of towel, with 7 ~ 9 with core lumbar puncture needle from the selected puncture point vertical puncture, there is a sense of falling into the amniotic cavity, pull out the core of the needle, see the amniotic fluid overflow or empty syringe back to see the amniotic fluid, connected to the 5 ml of levano has been pumped syringe, and then a small amount of amniotic fluid suction, to confirm that the needle is in the amniotic cavity, the liquid can be slowly injected, remove the syringe, insert the core of the needle, pull out the needle after the puncture point with sterilized gauze After the needle is withdrawn, the puncture point is covered with sterilized gauze and compressed for several minutes, and fixed with adhesive tape. If there is bright red blood or bloody amniotic fluid overflow from the blood sinus of the placenta or uterine wall in the needle puncture, the puncture needle should be moved upward or downward until there is clarified amniotic fluid overflow, and if necessary, another site should be selected for re-puncture. Generally, the needle can be inserted 1 or 2 times, and repeated puncture should be avoided to avoid infection, hematoma, or even amniotic fluid embolism. Mechanism: In addition to drug stimulation of uterine smooth muscle contraction, it can also kill the fetus, cause degeneration and necrosis of the meconium and placental tissue, and produce endogenous prostaglandins, which can further enhance contraction, soften the cervix, promote cervical ripening and cause abortion. Levano intra-amniotic injection for inducing labor is simple, inexpensive, safe and effective, with few serious complications, low infection rate and high success rate, its success rate of inducing labor reaches 96.4%, which is one of the most commonly used methods of inducing labor at present.
3. Mifepristone with misoprostol to induce labor
(1) Indications and contraindications ① Indications The termination of pregnancy at 15 to 27 weeks without contraindications; due to certain diseases, it is not suitable to continue the pregnancy; premature rupture of membranes, the failure of other methods of induced abortion; body temperature of not more than 37.5 ℃. ② contraindications Acute stage of various systemic diseases; acute inflammation of the reproductive organs or acute attacks of chronic inflammation, such as vaginitis, severe cervical erosion, pelvic inflammatory disease; maternal liver and kidney disease; asthma, hypertension, heart disease, epilepsy, glaucoma, thrombocytopenia and severe anemia; uterine deformities, cervix hard or scarred, etc.; gastrointestinal function abnormalities or electrolyte disorders. Mifepristone is contraindicated in pregnant women with adrenal disease, diabetes mellitus, abnormal liver function and hormone-related tumors, such as obvious uterine fibroids, breast cancer, ovarian cancer.
(2) Clinical application Mifepristone is a progesterone receptor antagonist, used in mid-pregnancy induction of labor directly on the uterine arteries on the estrogen and progesterone receptors, affecting the uterine arteries to the placenta blood supply, improve the sensitivity to endogenous prostaglandins, and endogenous prostaglandin synthesis can be increased, resulting in the metaphysis of tissue denaturation, edema, hemorrhage, necrosis, trophoblast cell apoptosis, the metaphyses and the chorionic villus membrane separated from the placenta fetal membranes discharge, and the uterine cervix collagen, the uterus and the uterus. At the same time, it can cause the collagen fibers of the cervix to degrade and undergo dissolution, causing the cervix to soften and dilate. Misoprostol is a synthetic PGE2 analog, which can soften the connective tissue of the cervix, degrade the collagen, and also cause uterine smooth muscle contraction. The combination of mifepristone and misoprostol shortens the induction of labor, reduces retained placental membranes, and decreases the clearance rate. In addition, in the case of maintaining the same dosage of Mifepristone, Misoprostol different ways of administration, the adverse reactions and dosage is not the same, to vaginal administration of adverse reactions less, the dosage is small; sublingual than oral effect is better, faster onset of action, but chills and fever and other adverse reactions, and the taste is poorer.
4. Levano with misoprostol to induce labor
(1) Indications and contraindications ① Indications The pregnancy is 15 to 27 weeks to terminate without contraindications; due to certain diseases, it is not suitable for the continuation of pregnancy; premature rupture of membranes, the failure of other methods of inducing labor; body temperature does not exceed 37.5 ℃. ② contraindications Acute stage of various systemic diseases; acute inflammation of the reproductive organs or acute attacks of chronic inflammation, such as vaginitis, severe cervical erosion, pelvic inflammatory disease; maternal liver and kidney disease; asthma, hypertension, heart disease, epilepsy, glaucoma, thrombocytopenia and severe anemia; uterine deformities, cervix hard or scarred, etc.; gastrointestinal function abnormalities or electrolyte disorders. Mifepristone is contraindicated in pregnant women with adrenal disease, diabetes mellitus, abnormal liver function and hormone-related tumors, such as obvious uterine fibroids, breast cancer, ovarian cancer.
(2) Clinical application Levano with Misoprostol to induce labor is a practical experience accumulated in recent years, which effectively solves the problems of passive dilatation of the cervix and long duration of labor induced by Levano, and improves the success rate of induced labor. Methods: Levano was injected into the amniotic cavity by puncture, and misoprostol was placed in the posterior vaginal vault immediately after the operation. Mechanisms: The intra-amniotic cavity injection of Rivanol is used for inducing labor in middle pregnancy with high success rate and few adverse reactions. It achieves the purpose of termination of pregnancy by stimulating uterine contraction, but after the delivery of the fetus and the placenta, necrotic fetal membranes are easy to be retained in the uterine cavity, which prolongs the time of vaginal bleeding and increases the amount of hemorrhage. Misoprostol has obvious excitatory effect on uterine smooth muscle and cervical dilatation, which can strengthen uterine contraction force and discharge the residues in the uterine cavity.
5. Fetal extraction by cesarean section
(1) Indications The pregnancy needs to be terminated due to systemic diseases in the 14th to 27th week of pregnancy, and the condition of the pregnant woman herself is not suitable for any other kind of induced abortion in the middle term; those who have failed to induce labor by water bladder or other methods; those whose body temperature is below 37.5℃. However, it is contraindicated in cases where the pregnant woman’s general condition is extremely weak and she is unable to perform the operation, and in cases where there is an infected lesion on the abdominal wall or serious skin disease.
(2) Clinical application Cesarean section refers to the use of surgical methods to directly open the uterine cavity to terminate pregnancy, because of its traumatic and complex operation is only used in cases where other methods of inducing labor can not be used or where the pregnancy needs to be terminated as soon as possible (e.g., pathological obstetrics or rupture of the uterus with a premonitory rupture). The indications for inducing labor should be strictly controlled, and the contractions should be actively prevented and controlled.