Post-term pregnancy

　　The complex causes of prolonged pregnancy have not been clarified yet. The evaluation of the factors that may lead to delivery can be many, including progesterone blockade, oxytocin stimulation, and fetal adrenal cortex hormone secretion, etc. Any single factor causing these hormone imbalances can lead to prolonged pregnancy. Therefore, prolonged pregnancy may be related to the following factors: an imbalance in the ratio of estrogen and progesterone; oral fetal malformation, such as anencephaly, related to insufficient secretion of fetal adrenal cortex hormones, genetic factors, etc.

　　The pathogenesis of prolonged pregnancy can be divided into 4 points:

　　① In cases of malpresentation, due to the weak stimulation of the fetal presenting part on the cervical internal os and the lower segment of the uterus, it is easy to have prolonged pregnancy.

　　② Anencephaly teratoma without polyhydramnios, due to the absence of the hypothalamus in the fetus, causes the hypothalamus-adrenal cortex axis to develop poorly. The adrenal cortex hormones and the precursor of estrone, 16α-hydroxysulfated dehydroepiandrosterone, produced by the fetal adrenal cortex, and the small and irregular fetus are not enough to stimulate the cervical internal os and the lower segment of the uterus to cause uterine contractions, and the gestational age can last up to 45 weeks.

　　③ Lack of placental sulfatase, a rare sex-linked recessive genetic disease, seen only in male fetus cases, where the fetal placental unit cannot convert the less active dehydroepiandrosterone into estradiol and estrone, leading to prolonged pregnancy. If the level of estrogen in the plasma does not increase after injecting dehydroepiandrosterone into the pregnant woman, it can be diagnosed.

　　④ Insufficient secretion of endogenous prostaglandins and estradiol, with an increased level of progesterone. Prolonged pregnancy is caused by an imbalance in the ratio of estrogen and progesterone, leading to a dominant role of progesterone, inhibiting prostaglandins and oxytocin, causing the uterus not to contract and delaying labor.

　　Prolonged pregnancy can also lead to macrosomia and difficult labor in the fetus. Moreover, this condition can increase the perinatal mortality rate of the fetus. The incidence of prolonged pregnancy is approximately 4-14% (average 10%), and all medical statistics show that the probability of complications in the fetus increases significantly after 42 weeks of pregnancy, especially many problems occur during the process of delivery and shortly after birth. One report indicates that the perinatal mortality rate of a fetus born at 40 weeks is 1.5 per thousand, while if it is delayed to 44 weeks, the perinatal mortality rate will increase to 6.9 per thousand.

　　Fetal asphyxia and meconium aspiration are the most common complications, with other complications including shoulder dystocia, macrosomia, cesarean section, and early-onset neonatal seizures. In prolonged pregnancy, 15-20% of the amniotic fluid may contain meconium, and 2-10% may have macrosomia (fetal weight exceeding 4,000 grams). Therefore, both parents and medical staff should have a correct understanding of prolonged pregnancy and appropriate treatment.

　　Prolonged pregnancy has a significant impact on both the fetus and the pregnant woman. Pathological changes in the placenta can lead to fetal distress or macrosomia, causing difficult labor, both of which increase the perinatal mortality rate and the incidence of neonatal asphyxia. For the mother, fetal distress, malpresentation, and prolonged labor can significantly increase the rate of cesarean sections. Due to fetal meconium stained amniotic fluid, fetal skin, amniotic membrane, and umbilical cord, the fetus is born with low scores and a high mortality rate. There are mainly the following 6 common symptoms.

　　①Pregnancy duration ≥42 weeks.

　　②The fetal movements are less than before.

　　③The fundal height and abdominal circumference are larger or smaller than the gestational age.

　　④The ultrasound indicates a decrease in amniotic fluid.

　　⑤The fetal heart electronic monitor NST test shows abnormalities.

　　⑥The urine estrogen/24-hour value is low.

　　In the first half year before pregnancy, it is necessary to record each menstrual cycle in time to be able to predict a more accurate expected date of delivery. After 2 months of amenorrhea, it should be checked in the hospital, and regular prenatal examinations should be carried out regularly, especially at least once a week after 36 weeks of pregnancy. After pregnancy, implement the three-level management of maternal and child health care, promote the use of maternal and child health care handbooks, choose delivery methods that are beneficial to both mother and child, and plan to terminate pregnancy in a timely manner to reduce the incidence of post-term pregnancy. Accurately diagnose post-term pregnancy, and obstetricians should take early induction measures for all pregnancies reaching 41 weeks based on careful verification of the expected date of delivery, combined with B-ultrasound amniotic fluid monitoring, fetal heart monitoring, etc., in order to reduce the perinatal morbidity and mortality rate caused by post-term delivery and fetal overripeness.

　　Pregnant women can also self-test fetal movements. If the number of fetal movements within 12 hours is less than 20 times, it indicates abnormal fetus; if it is less than 10 times, it indicates that the fetus is in great danger, and immediate medical treatment should be sought. If a pregnant woman is diagnosed with post-term pregnancy, she should be diagnosed and induced by a doctor in a timely manner.

　　Pregnancy is an important and special period in a woman's body, and enough attention should be paid to post-term pregnancy. The main methods to check post-term pregnancy are to verify the expected date of delivery and judge placental function.

　　(i)Verifying the expected date of delivery

　　Accurately verify the expiration of the expected date of delivery, if the regular menstrual cycle is not accurate, the calculated expected date of delivery is not reliable, so attention should be paid to:

　　①Inquire in detail about the changes in regular menstrual periods, and whether there are any contraceptives taken that may delay the ovulation period.

　　②Calculate the expected date of delivery based on the ovulation period when the basal body temperature before pregnancy increases.

　　③For couples living apart, the expected date of delivery should be calculated based on the date of sexual intercourse.

　　④Estimate based on the time when the early pregnancy reaction first appeared (appearing at 6 weeks of pregnancy).

　　⑤For those who have undergone gynecological examination in the early pregnancy, the expected date of delivery should be calculated according to the size of the uterus at that time.

　　⑥When hearing the fetal heart through a stethoscope on the abdominal wall, the gestational age is at least 18-20 weeks.

　　⑦B-ultrasound examination: Determine the gestational sac diameter in the early pregnancy, and measure the fetal biparietal diameter, femur length, etc. in the second trimester and later, and calculate the expected date of delivery based on the change of amniotic fluid volume in the late stage.

　　⑧The uterus conforms to the size of a full-term pregnancy, the cervix is mature, the amniotic fluid level gradually decreases, the weight of the pregnant woman no longer increases or slightly decreases, and it should be considered as post-term pregnancy.

　　(ii)Judging placental function

　　①Fetal movement counting: Due to the different levels of activity among fetuses, the number of fetal movements felt by different pregnant women varies greatly. It is generally believed that the cumulative number of fetal movements within 12 hours should not be less than 10 times, so if the number is less than 10 times within 12 hours or decreases by more than 50% each day, and cannot recover, it should be considered as poor placental function and the fetus is experiencing oxygen deficiency.

　　②Determine the urine estriol and creatinine (E/C) ratio: The E/C ratio is determined by a single urine test. Under normal circumstances, the E/C ratio should be greater than 15. If the E/C ratio

　　③Fetal monitor detection: Non-stress test (NST) twice a week. A reactive NST indicates that the fetus is not experiencing hypoxia. An NST without a reaction requires a contraction stress test (CST). If CST shows multiple late decelerations in fetal heart rate, it indicates that the fetus is hypoxic.

　　④Ultrasound monitoring: 1-2 times of B-ultrasound monitoring per week to observe fetal movement, fetal muscle tone, fetal respiratory-like movement, and amniotic fluid volume. The diameter of the amniotic fluid shadow area

　　⑤Postpartum examination of the fetus and its accessories. Good placental function is manifested as 'post-term macrosomia', while the other part is manifested as small-for-gestational-age, yellow skin, green hands and feet, calcified placenta obstruction, less amniotic fluid, and sticky amniotic fluid.

　　Pregnancy and postpartum physiological conditions are special for pregnant women. During pregnancy, the blood of the internal organs and meridians is all focused on the Chong and Ren meridians to nourish the fetus. It is necessary to avoid spicy and hot foods such as alcohol, dried ginger, pepper, chili, and dog meat to prevent injury to the Yin and fluid and affect pregnancy; in the later stages of pregnancy, due to the gradual growth of the fetus, it is easy to cause Qi stasis, so it is best to eat less flatulent and astringent foods such as sweet potatoes and potatoes. After childbirth, there is often deficiency and blood stasis, and at the same time, it is necessary to breastfeed the baby, so it is best to eat easily digestible and nutritious protein-rich foods.

　　Pregnant women with prolonged pregnancy can engage in exercise to induce labor to alleviate the symptoms of prolonged pregnancy. For example, breast massage. If the pregnant woman starts daily with a moist, warm soft cloth applied to the breasts from the 39th week of pregnancy and gently massaged, this will stimulate the pituitary gland to secrete oxytocin, thereby reducing the incidence of prolonged pregnancy to 5%. It is important to alternate between the two breasts, with 15 minutes of hot compress and massage alternation, three times a day, each for an hour. Walking can help the fetus descend into the pelvis, relax the pelvic ligaments, and prepare for delivery. It is best for the mother to walk, massage, and talk to the baby while walking. Walking can be scheduled twice a day, each for about 30 minutes, or three times a day, each for 20 minutes. It is best to choose a tranquil environment for walking, away from pollutants, and not to walk near highways. Pre-natal exercises are very popular abroad. Exercises not only help the fetus enter the pelvis but also increase the elasticity and resilience of the pelvic floor muscles. Climbing stairs can exercise the muscle groups of the thighs and buttocks, and help the fetus enter the pelvis, so that the first stage of labor comes as soon as possible.

　　If the expected delivery date has passed by more than a week without any signs of labor, it is even more important to actively seek medical examination. The doctor should assess the fetus's size, amniotic fluid level, placental function, fetal maturity, or diagnose the pregnancy as prolonged through an ultrasound.

　　(一)Pre-natal treatment

　　Prolonged pregnancy has been diagnosed. If any of the following conditions occur, immediate termination of pregnancy should be considered:

　　①Cervical condition mature.

　　②Fetus weighing ≥4000g or IUGR.

　　③Total fetal movement count within 12 hours

　　④Continuous low E/C ratio.

　　⑤Insufficient amniotic fluid (amniotic fluid dark area)

　　⑥Complications of moderate or severe pregnancy-induced hypertension (PIH).

　　The method of terminating pregnancy should be determined according to the situation. For those with mature cervix, artificial rupture of membranes should be performed, and delivery can be carried out vaginally under strict monitoring if the amniotic fluid is abundant and clear. For those with immature cervix, cervical ripening drugs, oxytocin, or prostaglandin preparations can be used for induction; in cases of poor placental function or signs of fetal distress, cesarean section should be performed as soon as possible to end labor regardless of the maturity of the cervix.

　　(Two) Intrapartum Management

　　In cases of prolonged pregnancy, although the fetus has sufficient reserve capacity to ensure normal antenatal monitoring tests, the significant increase in uterine contraction stress during labor exceeds its reserve capacity, leading to latent fetal distress or even death. This should be fully recognized. Timely application of fetal monitors, timely detection of problems, and emergency measures should be taken to choose cesarean section in a timely manner to end labor and save the fetus. Indications for cesarean section include:

　　①Induction failure.

　　②Long labor with unsatisfactory descent of the presenting part of the fetus.

　　③Signs of fetal distress during labor.

　　④Dysmaturity of the pelvis and the head.

　　⑤Large for gestational age (LGA).

　　⑥Breech presentation with mild pelvic narrowing.

　　⑦Elderly primiparous women.

　　⑧Insufficient, thick, and meconium-stained amniotic fluid after membrane rupture.

　　To avoid fetal hypoxia during labor, oxygen should be given to the mother in a timely manner, intravenous glucose infusion should be performed, and fetal heart monitoring should be carried out. For suspected fetal anomalies, B-ultrasound examination should be performed, and all preparations for fetal rescue should be made. In cases of prolonged pregnancy, fetal distress and amniotic fluid meconium staining are often present, and corresponding preparations should be made during delivery. It is required to use a vacuum aspirator or a suction catheter to remove the secretions from the fetal nasopharynx before the fetal shoulder is delivered. For those with fetal meconium exceeding the vocal cords after delivery, the contents of the trachea should be aspirated under direct laryngoscopy, and detailed records should be made. The incidence and mortality rate of overdue infants are high, and neonatal asphyxia, dehydration, hypovolemia, and metabolic acidosis should be detected and treated in a timely manner.

　　(Three) Prognosis

　　Overdue infants may have symptoms such as emaciation and loose skin, and severe cases may produce aspiration pneumonia and hypoxic brain damage, manifested as difficulty breathing, groaning, cyanosis, or convulsions. The longer the overdue period, the higher the mortality rate, and survivors may have neurological sequelae. Therefore, when the pregnancy exceeds 42 weeks, the mother should see a doctor in a timely manner. The doctor will decide on the plan to terminate the pregnancy according to the actual situation, such as induction or cesarean section, etc.