overdue pregnancy
Introduction
Introduction to expired pregnancy Pregnancy reaches or exceeds 42 weeks and is called an expired pregnancy. Its incidence is about 5-12% of the total number of pregnancies. Fetal perinatal morbidity and mortality in expired pregnancies have increased. At present, scholars generally believe that expired pregnancy is a high-risk pregnancy, and its perinatal mortality is significantly higher than normal gestational pregnancy, and the longer the expiration, the higher the mortality. basic knowledge Probability ratio: 2.1% of pregnant women Susceptible people: good for pregnant women Mode of infection: non-infectious Complications: dystocia, oligohydramnios, meconium aspiration syndrome, intrauterine distress, fetal growth restriction, giant
Cause
Expired pregnancy cause
Low estrogen levels (35%)
Although the mechanism of labor is very complicated, the level of estrogen in blood is closely related to labor. Expired pregnancy may be related to the low level of blood estrogen, but in a large number of expired pregnancies, there is no estrogen level lower than normal. Direct proof of pregnancy.
Placental sulfate lipase deficiency (20%)
Placental sulfatase deficiency is a rare concomitant recessive genetic disease. This disease was reported by Ryan in 1980. Although the fetal adrenal gland produced a sufficient amount of 16-OH-DHEAS, In the absence of placental serotonase, it is not possible to convert this less active dehydroepiandrosterone into estradiol and estriol, resulting in an overdue pregnancy.
The head basin is not called (20%)
In the expired pregnancy, some of the fetuses are large, the fetal head is not in the basin, and the cervix is not stimulated by the proper stimulation, which delays the onset of labor. This is the reason why it is more common.
Genetic (5%)
A small number of women have a longer gestation period, and several fetuses have expired pregnancies. There are fashions in a family, indicating that this tendency may be related to heredity.
Pathogenesis
The growth and development of any organism has a normal to aging process, and the placenta is no exception. From normal pregnancy to expired pregnancy, the placenta also has some signs of aging, but not all placenta will appear in the expired pregnancy. Performance, however, the frequency of abnormal performance increases.
Under normal circumstances, the placenta is fully developed at the fifth pregnancy month. It can supply oxygen and various nutrients adequately for fetal growth and development. When it is 36 weeks pregnant, its growth function has reached At the peak, although some of the placenta still maintain a good functional state, most of them, the growth rate is slower, and the growth rate is slower after the full term of pregnancy. After 42 weeks of gestation, except for a few placenta, the growth has been Stop, aging performance is increasingly obvious.
1. Changes in placenta to the naked eye: The placental infarct area and calcification of the placenta are more than normal placenta, and the individual placenta is smaller than normal, especially in the case of the fetus is too mature, and the fetal surface of the placenta sometimes has yellow staining.
2. Microscopic observation, mainly the reduction of villus vasculature, so the flow of villus perfusion is reduced, and there are secondary nodules and interstitial fibrosis; due to mild ischemia of the placenta, there are cytotrophoblasts in mild or medium Degree hyperplasia and thickening of basal membrane of trophoblast cells. Under electron microscope, it has been reported that the microvilli on the surface of the syncytium cells is significantly reduced, the vesicles in the syncytium cells are reduced, the endoplasmic reticulum vacuoles, mitochondria, Golgi complex and secretory granules. Reduce the thickening of the trophoblastic basement membrane.
The cessation of placental growth means that the supply of oxygen and nutrients is no longer increasing and there is a tendency to decrease. The placenta is in a state of chronic insufficiency, accounting for 5% to 12% of all pregnancies, and in the range of 20% to 40%. The above changes can be seen in the placenta examination of the death of the child. The most important effect on the fetus is chronic hypoxia, and 60% to 70% of the newborns who die after delivery are caused by chronic hypoxia (Minning et al., 1982).
Interestingly, recent Smith and Barkel (1999) found that placental apoptosis (programmed cell death) in 41-42 weeks of gestation was significantly higher than the placenta between 36 and 39 weeks of gestation, which may provide a new direction for the study of expired pregnancy. .
3. The fetus is thin and weak. The fetus with the above changes in placenta is different from the normal fetus. It is thin and small. Cliford (1957) divided these newborns with dysmaturity syndrome into 3 levels:
Grade I: Due to the lack of subcutaneous fat, the limbs are slender, the skin is dry and wrinkled, such as parchment, fetal fat and lanugo, nail length, neonatal malnutrition, but no meconium pollution, skull is hard, But the face reaction is still alert.
Level II: Neonatal performance is grade I, but with amniotic fluid containing meconium, meconium can stain the surface of the skin, placenta, membrane and umbilical cord, but no yellow staining.
Grade III: Neonatal performance is grade I. In addition to meconium contamination, neonatal nails, yellowish skin, placenta, membranes and umbilical cord surfaces are stained yellow-green.
4. Pathophysiology: The overdose pregnancy with placental lesions, the main pathophysiological changes of the fetus is a progressive process of chronic hypoxia and dystrophic disorders. The pathophysiological changes can be summarized as follows: 1 placenta is usually after 41 weeks of gestation Growth stopped; 2 placenta may have degenerative changes; 3 fetal growth stopped; 4 oxygen and nutrient supply decreased; 5 fetal-placental unit function pathological tendency increased; 6 meconium contamination rate increased; 7 amniotic fluid volume decreased; Internal distress and perinatal mortality increased.
Although the pregnancy has expired but the placental function has not been attenuated, the greatest risk is that the fetus is too large, the fetal weight 4000g or 4500g compared with the 40-week pregnancy, the incidence is significantly increased, the fetal malformation problem is expired Pregnancy is also noted, because fetal malformations in expired pregnancies are also higher than normal pregnancy, according to Ahn and Phelan (1989), the deformity rate is 2.5%, which is more common in nervous system malformations.
Fetuses with expired pregnancies are often over-mature. Over-ripe children are independent of the concept of expired pregnancies. They refer to a group of pathological conditions in which the fetus develops more than normal in the uterus. Clifford (1954) divides over-mature children into 3 degrees. Once: amniotic fluid; second degree: skin stained green; third degree: skin is yellow-green, 41-43 weeks gestation, the incidence of over-mature children is 10%, up to 33% in 44 weeks, over-ripe children are thinner, Zhang The eyes are "alert", so the face is like the old man, the skin is wrinkled, especially the bottom of the palm of the hand is more obvious, and often has peeling of the sheet, the nail is longer, it is very important that the over-ripe child is more prone to suffocation, meconium Perinatal mortality is significantly increased by inhalation and brain damage.
One of the reasons for oligohydramnios is the reduction of fetal renal blood flow in expired pregnancy (Veille et al., 1993). The reduction of amniotic fluid and the reduction of fetal amniotic fluid swallowing is reduced by the amount of urine, and the decrease in urine output is the cause of too little amniotic fluid, Frimmer et al. 1990) Ultrasound diagnosis was performed on 38 cases of 42-week pregnant women. The hourly fetal bladder volume was measured continuously. It was found that the reduction of urine output is the cause of oligohydramnios. Because some amniotic fluid is derived from the secretion of placenta, the placenta source is not excluded. The possibility of reduction is that when the oligohydramnios is too small, the umbilical cord is easily stressed, resulting in intrauterine distress. LJeveno (1984) reported 727 cases of fetal distress in the production of expired pregnancy, and the fetal heart rate showed three abnormal changes: 1 sustained deceleration, 3/4 Emergency cesarean section belongs to; 2 mutation slowdown: 3 baseline jump, fluctuation more than 20 times / min, and combined with oligohydramnios, the author believes that the above changes are not due to placental dysfunction, but the result of umbilical cord compression of oligohydramnios .
5. The impact of fetal babies
(1) Fetal growth restriction: The definition of fetal growth restriction is that the birth weight is lower than the standard birth weight of the same sex in the gestational age by 2 standard deviations (2SD), and one third of the expired pregnancy and stillbirth is due to fetal growth. Limit, Divon et al (1998) and Clausson et al (1999), analysis of nearly 700,000 births from 1987 to 1995, fetal growth restriction in 42 weeks of expired pregnancy is an important cause of stillbirth, in the unexpired term Fetal growth restriction during pregnancy is also a major cause of stillbirth.
Alexander et al (2000) analyzed 355 outdated gestational infants 42 weeks and weight third percentile, compared with 14 520 infants weighing more than the third percentile, and found that growth-limited infants regardless of mortality Or the morbidity rate increases.
(2) Placental dysfunction: The organ of the human body generally has the same survival life and life span, and the function of the placenta is to maintain the growth and development of the fetus, so the placenta has the same period of existence as the pregnancy, theoretically the growth of the fetus Mature, the function of the placenta has been completed, clinically found that the incidence of intrauterine hypoxia in the 42 weeks of pregnancy increased, therefore, it can be inferred that the placental function has some degree of decline in some aspects.
As early as the 1950s, Clifford (1954) proposed the theory of placental aging in expired pregnancy, but in the following 40 years, the basis of placental morphology could not be found, Larsen et al (1995), Smith and Barker (1999) found 41 ~ Compared with the placenta of 36 to 39 weeks of gestation, the apoptosis of the former is significantly increased. The apoptosis is the normal process of cell death. It is a physiological process, combined with the fact that the placenta is a finite living organ. Death can be considered as a sign of aging of organs.
One of the main functions of the placenta is oxygen exchange between the mother and the child. If the umbilical venous oxygen saturation is reduced, it will indirectly prove that the placental oxygen exchange function is reduced. Since the oxygen partial pressure is the only stimulating factor of erythropoietin, the red blood cells are measured. The production factor can indirectly presume blood oxygen saturation and indirectly measure placental function. Jazayeri (1998) measured 124 cases of umbilical cord blood erythropoiesis during normal delivery of 37-43 weeks of pregnancy, and found that cord blood erythropoiesis increased after 41 weeks of gestation.
After 42 weeks of gestation, the weight of the fetus still increases, at least 42 weeks of gestation (Nahum et al., 1995). The increase in fetal weight requires the placenta to transport nutrients, but gas exchange and nutrient transport are not the same mechanism, and the transport mechanism of different nutrients is also Different, so the fetal weight can still increase in 41 to 42 weeks and does not contradict the damage of oxygen delivery function after 41 weeks.
Prevention
Overdue pregnancy prevention
First of all, we must correctly calculate the expected date of delivery - pregnant women should be clear about the date of the last menstrual period; pregnant women with irregular menstruation can be calculated according to the early pregnancy reaction and the date of fetal movement, or combined with the gynecological examination of the uterus in early pregnancy, comprehensive analysis and judgment; B-ultrasound, Can help to infer the expected date of delivery.
Close monitoring - Once the pregnancy is determined to be out of date, you should closely observe the survival of the fetus in the uterus, pay attention to the risk of death of the fetus due to lack of oxygen, the simplest method is several fetal movements, pregnant women should be raised from 38 weeks of gestation The habit of fetal movement, if the number of activities of the fetus in less than 10 hours is less than 10 times, it should be paid attention to. In addition, it can also go to the hospital for fetal heart rate monitoring and placental function examination.
Complication
Expired pregnancy complications Complications dystocia oligohydramnios meconium aspiration syndrome fetal intrauterine distress fetal growth restriction giant
Overdue pregnancy during childbirth, often due to decreased amniotic fluid, large fetus, hard skull, poor plasticity, prone to dystocia, affecting the fetus, prone to placental aging, degeneration, directly affect fetal oxygen and nutrient supply, in severe cases Death due to suffocation due to lack of oxygen.
1. Too little amniotic fluid: over-ripe children are prone to oligohydramnios. The sheep pool is 1cm as the diagnostic criteria for oligohydramnios (Trimmer, 1990). The amount of amniotic fluid decreased from 38 weeks after pregnancy, and decreased significantly to 40 weeks. At 42 weeks, the prevalence of oligohydramnios was 88%.
During the pregnancy, the amniotic fluid decreased gradually after 38 weeks of gestation, more obvious after 40 weeks. After 42 weeks, the expired pregnancy often combined with oligohydramnios, which reflected the status of placental function and explained the seriousness of meconium contamination. Because amniotic fluid is reduced, meconium discharge is more viscous than normal in the dilution of a small amount of amniotic fluid. If inhaled, the neonatal meconium aspiration syndrome is more serious; in addition, the possibility of umbilical cord compression is also increased.
2. Intrauterine distress: the placenta of expired pregnancy, due to gradual degradation, placental function decline, the saturation of oxygen in the fetal umbilical vein blood decreases, so the oxygen and nutrients supplied to the fetus gradually decrease, and the more mature the fetus, the hypoxia The worse the tolerance, so when the uterus contraction is strong, the expired fetus is prone to distress and even death in the uterus.
3. Fetal growth restriction: Due to the aging of part of the expired pregnancy, the incidence of fetal growth restriction in the overdue pregnancy is much higher than that of the fetus delivered during the normal gestation period.
4. Huge children: In the case of expired pregnancy and placental function is not limited, the fetus continues to grow and develop, so the incidence of weight 4000g is not lower than the normal gestational age.
Symptom
Expired pregnancy symptoms Common symptoms Uterine height is lower than the number of weeks of pregnancy Pregnant women are not pregnant due to abdominal pain Late pregnancy or labor... Cord blood circulation disorder
There are mainly the following 6 common symptoms.
1 pregnancy period 42 weeks.
2 fetal movement decreased compared with the previous.
3 The height of the bottom of the palace, the abdominal circumference is larger or smaller than the gestational age.
4 ultrasound prompts the reduction of amniotic fluid.
5 fetal heart rate electronic monitor NST test abnormalities.
6 urinary estriol / 24 hours value is low.
Examine
Overdue pregnancy check
First, determine the placental function 1. Fetal movement count; 2. hPL measurement; 3. Urinary E3 ratio determination; 4. B-ultrasound, including double apical meridian, placental function grading, amniotic fluid volume, etc.; 5. Amniocentesis; 6. NST , OCT test, etc.
Second, the fetal electronic monitor detection.
Third, B-ultrasound detection has become an important tool for predicting the expectation period of pregnant women. The measurement content is mainly crown-rump length, double top diameter, long femur, time comparison in B-ultrasound, early pregnancy The most accurate time; in the early pregnancy with the head and hip length (mm) projection, the expected delivery period is within ±4 days; to 16 to 26 weeks, the double-diameter and femur length are used to calculate the expected date of delivery, the accuracy is about ± 1 week, after which, Accuracy is within ±2 to 3 weeks.
Fourth, amniocentesis.
V. Determination of estrogen In the third trimester of pregnancy, the levels of estrogen in the blood and urine of pregnant women are significantly increased. By the end of pregnancy, it is 1000 times that of non-pregnancy, and E3 accounts for 90% of the total amount of estrogen. Therefore, the E3 content in urine can be measured. Understand the function of the placenta, under normal circumstances, the daily total amount of E3 in pregnant women should be above 15mg. For example, if the amount of E3 in the urine is reduced to 10mg or below in 24h, the placental function is reduced, but the pregnant woman should collect 24h urine volume and carry it for inspection. Inconvenience, later changed to E / C ratio method (C is creatinine), because the amount of creatinine secretion is very constant, so you can use a single urine to determine the ratio of estriol to creatinine, the normal situation should be >15, such as A ratio of <10 also indicates a decrease in placental function.
Plasma free E3 determination also helps to determine placental function, its abnormal performance is often before the change of E3 in urine. If the plasma free E3 value is <4ng/ml, the Apgar low score is the majority when the newborn is delivered, although the E3 concentration in saliva is The concentration of E3 in the blood is 1/1000, but the change is consistent with the blood E3 concentration. Because saliva is convenient to carry, in the mid-1980s, radioimmunoassay was used to measure the E3 concentration in saliva to reflect the report of placental function, but no matter which one The E3 determination method is not as good as NST and B ultrasound, which can directly reflect the fetal condition. It is currently used less clinically. However, there are still some units in the expired pregnancy for the determination of E3 value of blood or urine, which still has certain significance in clinical practice. .
Sixth, placental lactogen (HPL) determination, with the development of the placenta and blood levels increased, reached the peak at 35 weeks of pregnancy, once the placenta was delivered, 7 hours after the blood has not been measured HPL, HPL blood concentration can reflect the size of the placenta And functional status, available in the premature pregnancy to understand the fetus, but because of its large range of variation, and can not reflect the real-time fetal situation, it is rarely used clinically.
Diagnosis
Diagnostic diagnosis of expired pregnancy
diagnosis
Verify the expected date of delivery
Accurately verify that the expected date of delivery is expired. If the menstrual cycle is not accurate, the estimated expected date of delivery is not reliable. Therefore, it should be noted that:
1 Inquire about the regular menstrual variation in detail, and whether or not to take birth control pills to delay the ovulation period.
2 According to the ovulation period of basal body temperature increase before pregnancy, the expected date of birth is estimated.
3 The couples are separated and should be extrapolated based on the date of sexual intercourse.
4 Estimated based on the onset of early pregnancy response (appearing at 6 weeks of gestation).
5 gynecological examinations were performed in the early pregnancy, according to the size of the uterus at that time.
6 When the fetal heart is heard through the abdominal wall with the earpiece, the gestational age is at least 18-20 weeks.
7B type ultrasound examination, the gestational sac diameter was measured in early pregnancy, the fetal head and hip length, the double top diameter, the femur length were measured after the second trimester, and the expected delivery period was calculated according to the change of amniotic fluid volume.
8 The uterus meets the size of the full-term gestational age, the cervix is mature, the amount of amniotic fluid is gradually decreasing, and the weight of the pregnant woman is no longer increased or slightly reduced, and should be regarded as an expired pregnancy.
Judging the function of the placenta
1 fetal movement count: Due to the different activities of each fetus, the number of fetal movements of different pregnant women varies greatly. It is generally believed that the cumulative number of fetal movements within 12 hours shall not be less than 10 times, so less than 10 times within 12 hours or more than 50% daily. However, it can not be recovered, it should be regarded as dysfunction of the placenta, and the fetus has hypoxia.
2 Determination of urinary estriol and creatinine (E / C) ratio: E / C ratio was measured by single urine. The E/C ratio should be greater than 15 under normal conditions. If the E/C ratio is <10, the placental function is reduced.
3 fetal monitor test: no stress test (NST) twice a week, NST response type suggests that the fetus is not hypoxic, NST non-reactive type need to do uterine contraction stress test (CST), CST repeated fetal heart Late deceleration, suggesting that the fetus has hypoxia.
4 Ultrasound monitoring: B-mode ultrasound monitoring 1-2 times a week to observe fetal movement, fetal muscle tone, fetal respiratory movement and amniotic fluid volume. The amniotic fluid dark area <3cm, suggesting that the placental function is incomplete, <2cm fetal risk. Color ultrasound Doppler examination can still determine fetal placental function and fetal safety by measuring fetal umbilical blood flow.
5 postpartum examination of the fetus and appendages, the performance of the placenta is good as "expired giants", the other part of the performance is a small sample, skin yellowing, green hands and feet, placental calcification infarction, less amniotic fluid, thick.
Differential diagnosis
Root nucleus gestational age, hPL measurement, urine E3 ratio measurement, B-ultrasound, amniocentesis, NST, OCT test and other normal pregnancy identification.
