Multiple pregnancies

　　Multiple pregnancies are not common, but some people may still experience multiple pregnancies. So, why do pregnant women have multiple pregnancies? In fact, there are many reasons for multiple pregnancies, and the following are some common reasons.

　　One, Age and Number of Pregnancies

　　Age has no significant effect on the incidence of monozygotic twins, but the incidence of multifetal twins increases significantly with age. The more times a woman gives birth, the higher the incidence of multiple pregnancies.

　　Two, the Application of Ovulation-inducing Drugs

　　Multiple pregnancies are a major complication of drug-induced ovulation. They are related to individual response differences and excessive dosage. During the treatment with human menopausal gonadotropin (HMG), ovarian hyperstimulation is likely to occur, leading to multiple ovulations, increasing the chance of multiple pregnancies by 20% to 40%.

　　Three, Genetic Factors

　　Multiple pregnancies have a familial tendency. If one of the couple has had multiple deliveries in the family, the incidence of multiple pregnancies increases. Monozygotic twins are not related to heredity. Dizygotic twins have a clear hereditary history. If a woman herself is one of the dizygotic twins, the probability of delivering multiple fetuses is higher than that of her husband being one of the dizygotic twins, indicating that the mother's genotype has a greater impact than the father's.

　　4, Endogenous gonadotropins

　　The occurrence of spontaneous dizygotic twins is related to a higher level of follicle-stimulating hormone (FSH) in the body. Mastin et al. (1984) found that the level of FSH in the early follicular phase of blood from women delivering multiple fetuses is significantly higher than that from women delivering singletons. The rate of dizygotic twins increases one month after the woman stops taking birth control pills, which may be due to an increase in the secretion of gonadotropin by the pituitary gland, leading to the maturation of multiple primordial follicles.

　　Multiple pregnancies have an impact on both the mother and the fetus.

　　1, Complications in pregnant women

　　1, Anemia

　　Pregnant women with multiple pregnancies have an increased need for iron and folic acid, and the relative dilution of blood is caused by the significantly increased plasma volume compared to singleton pregnancies, leading to anemia. Anemia in multiple pregnancies is 2.4 times higher than that in singleton pregnancies. Anemia during pregnancy can have adverse effects on both the mother and the fetus, such as anemia cardiopathy, gestational hypertension, fetal growth retardation, fetal distress in utero, postpartum hemorrhage, and puerperal infection, etc.

　　2, Pre-eclampsia

　　The incidence of gestational hypertension in multiple pregnancies reaches 40%, which is four times higher than that in singleton pregnancies. It often occurs early and is more severe. Due to the increased blood volume and uterine tension in pregnant women with multiple pregnancies, it is easier to have complications such as placental abruption and heart failure in pregnant women.

　　3, Polyhydramnios

　　The incidence of polyhydramnios in multiple pregnancies is about 10%, and the incidence of monozygotic twins is four times higher than that of dizygotic twins. When polyhydramnios occurs, attention should be paid to exclude malformations of the nervous system and fetal digestive tract, etc.

　　4, Complications during delivery

　　⑥A singleton multiple pregnancy is not an indication for cesarean delivery. Delivery methods can be chosen under the guidance of a doctor according to individual circumstances. However, multiple pregnancies are prone to the following complications:

　　①Due to the excessive expansion of the uterus in multiple pregnancies, the uterine muscle fibers are excessively stretched, which is easy to cause uterine contraction weakness during labor, leading to prolonged labor and an increased risk of postpartum hemorrhage.

　　②When there is an excessive amount of amniotic fluid, due to increased intrauterine pressure, it is easy to have an early rupture of membranes and umbilical cord prolapse.

　　③In cases of multiple pregnancy, each fetus is usually smaller than a singleton fetus, and it is easy to have abnormal fetal position. After the first fetus is delivered, the second fetus has a larger range of movement, and it is easy to turn into a transverse position.

　　④During delivery, after the first fetus is delivered, the uterine cavity volume suddenly decreases, and the placental attachment area abruptly shrinks, so placental abruption may occur, directly threatening the life of the second fetus and the safety of the mother.

　　⑤When the first fetus is breech and the second fetus is in vertex position during delivery, if the first fetal head has not been delivered yet and the second fetal head has already descended into the pelvic cavity, it is easy to have a neck lock between the two fetal heads, causing dystocia, although this is rarely seen in clinical practice. This situation often occurs in cases where the fetus is small and the pelvic cavity is large, or in cases of multiple fetuses in a single amniotic sac or in cases where the second fetus has an early rupture of membranes.

　　Second, perinatal complications

　　The perinatal mortality rate in twin pregnancies is high, related to preterm birth, fetal growth restriction, fetal malformation, and umbilical cord abnormalities. Twin pregnancies with monochorionic placentas have the risk of developing their special complications, such as twin-to-twin transfusion syndrome, loss of twins, reversed arterial perfusion in twins, etc.

　　1. Twin-to-twin transfusion syndrome

　　Vascular anastomosis in twin placentas: The rate of vascular anastomosis in monochorionic twin placentas is as high as 85%-100%. It includes three types: arterial-to-arterial, venous-to-venous, and arteriovenous anastomosis. The superficial part of the fetal surface of the placenta is mostly anastomosed in an arterial-to-arterial manner, and a few are venous-to-venous anastomosis. In the deep part of the placental tissue, the arterial-to-venous anastomosis of the placental lobes exists with a difference in blood pressure. About 15% of monochorionic twin pregnancies occur twin-to-twin transfusion syndrome (TTTS). The recipient fetus shows increased blood volume, polyhydramnios, enlargement of the heart or heart failure with edema; while the donor fetus shows reduced blood volume, oligohydramnios, and growth restriction. Without intervention, the mortality rate of severe twin-to-twin transfusion syndrome can reach 80-100%.

　　2. One fetus death in multiple pregnancies

　　In the early pregnancy, if one fetus of twins dies in utero, it has not been found to have any effect on the survivors. However, in the late pregnancy, if one fetus dies in utero, there is a possibility of late miscarriage, 90% of which occur within 3 weeks. Literature reports that coagulation function abnormalities may occur around 4 weeks after fetal death, but in clinical actual monitoring, the occurrence of coagulation function abnormalities is still rare. It needs to be reminded that in clinical observations, the risk of intrauterine fetal death in surviving fetuses in the late pregnancy increases, which may be related to placental thrombosis affecting abnormal placental function (there is still a lack of scientific research evidence), so strict and intensive surveillance is needed. In twins with multiple placentas, the prognosis of survivors is mainly affected by gestational age; while in monochorionic twins, the risk of one fetus dying in utero and the other fetus dying in utero is about 20%, and the risk of brain injury in surviving fetuses is about 25%.

　　3. Reversed arterial perfusion in multiple pregnancies

　　It is a complication of monochorionic twins. One fetus has a cardiac arrest, while the other fetus still receives partial blood perfusion from the cardiovascular system of the other fetus. The occurrence of this situation is very low, but the risk of intrauterine fetal death is very high due to factors such as intrauterine heart failure in the recipient fetus. Usually, umbilical cord ligation is used to separate the twins.

　　4. Inconsistent growth in multiple pregnancies

　　It refers to a weight difference of ≥20% between two fetuses in the same pregnancy. It may be related to placental factors (such as abnormal placental development like small size), chromosomal abnormalities, and twin-to-twin transfusion syndrome, among which 4% of the causes are due to inconsistent fetal gender.

　　5. Complete hydatidiform mole and coexisting fetus

　　One fetus has a normal placenta, while the other is a complete hydatidiform mole. Approximately 60% of women with multiple pregnancies coexisting with a normal fetus and a complete hydatidiform mole will require chemotherapy due to persistent trophoblastic tumors. There is no ideal treatment method at present, but the serum HCG of pregnant women and respiratory symptoms should be monitored.

　　The symptoms of multiple pregnancies are relatively obvious, and pregnant women with multiple pregnancies often have a family history, pre-pregnancy use of ovulation-inducing drugs, or a history of multiple embryo transfer in vitro fertilization. Early pregnancy reactions are often severe and last longer, and the uterine volume is significantly larger than that of a single pregnancy. In the late pregnancy, due to the excessively large uterus, the diaphragm may rise, the stomach may be full, breathing may be difficult, walking may be inconvenient, varicose veins in the lower limbs and edema, and other symptoms of compression.

　　The occurrence of multiple pregnancies is not common. Natural multiple pregnancies are not preventable, but behaviors that artificially promote multiple pregnancies, such as taking ovulation-inducing drugs, should be avoided and prohibited.

　　Multiple pregnancies refer to a situation where a single pregnancy has two or more fetuses, and the examination mainly includes two categories: obstetric examination and auxiliary examination.

　　1. Obstetric examination

　　The following situations should be considered for multiple pregnancies:

　　①The uterus is larger than the gestational age.

　　②Multiple limbs and two or more fetal heads can be felt in the abdomen during the middle and late stages of pregnancy.

　　③The uterus is larger, and the fetal head is smaller, not proportional.

　　④Two different frequencies of fetal heart sounds can be heard at different locations, or count the fetal heart rate for 1 minute at the same time, and the two sounds differ by 10 or more.

　　2. Auxiliary examination

　　①Ultrasound examination

　　Two fetal sacs can be seen in the early stage of pregnancy; in the middle and late stages of pregnancy, according to the ultrasound images of the fetal skull and spine, the accuracy rate of B-ultrasound diagnosis reaches 100%. The diagnosis of amniotic membrane mainly relies on ultrasound examination before 14 weeks of pregnancy: the gestational sacs are far apart in the early pregnancy, and if there is one amniotic cavity in each gestational sac, it is a hydatidiform multifoetal pregnancy; if there is a 'lambda' or 'multiplex' sign at the junction of the amniotic membranes, it is a hydatidiform multifoetal pregnancy. If two amniotic cavities are observed in one gestational sac, or two yolk sacs are displayed simultaneously in one amniotic cavity, it is a monochorionic multifetal pregnancy with amniotic membranes. If only one yolk sac is displayed in one amniotic cavity, it is a monochorionic single amniotic multifetal pregnancy. Multifetal pregnancies with different fetal genders in the middle trimester are usually monochorionic (multifetal). The diagnosis of chorionicity in the early pregnancy is very important for perinatal health care in the future.

　　②Doppler fetal heart sound stethoscope

　　After 12 weeks of pregnancy, two fetal heart sounds of different frequencies can be heard.

　　When the doctor informs the expectant mother that she may be carrying twins, the reaction of most pregnant women is shock. As a result, you will also receive more care and need to take more care of yourself than in a single pregnancy.

　　A healthy diet and adequate rest are very important because pregnant women need to consume more physical energy. It is best to increase the quantity and quality of nutrition and pay attention to a reasonable distribution of basic nutrients. If there is significant edema, it is appropriate to increase the intake of protein, and in necessary cases, intravenous administration of albumin preparations should be considered, and a low-salt diet should be followed. Iron and folic acid should be supplemented regularly to prevent anemia; after the middle stage of pregnancy, attention should be paid to rest, avoid sexual intercourse, and make preparations for delivery 4 weeks in advance.

　　If you are still working, it is best not to work full-time and to leave the workplace earlier than planned based on your specific circumstances. Try to arrange your work well and avoid overexertion. Taking care of yourself is the best way to take care of your baby. Multiple pregnancies are more physically demanding than single pregnancies, and your needs in many aspects will increase.

　　Eat more. Women with multiple pregnancies must eat more - at least an extra 1254 kilojoules of food per baby per day. Pregnant women need more protein, minerals, vitamins, and essential fatty acids. Maintaining weight is very important. During multiple pregnancies, your weight is more likely to increase. For women with normal weight, it is recommended to gain 15.75 to 20.25 kilograms during multiple pregnancies. However, many pregnant women cannot reach this weight because their bodies are too burdened.

　　Supplement iron. Iron supplementation is very important. Women with multiple pregnancies often suffer from iron deficiency anemia.

　　Do a check-up before exercising. During multiple pregnancies, swimming and walking are possible. However, before exercising, it is necessary to discuss the safety of this exercise with a doctor. Try to avoid strenuous exercise, stop excessive exertion immediately, and ensure the health of the pregnant woman.

　　Multiple pregnancies should be treated differently at different stages, mainly divided into pregnancy and delivery treatment. The following will introduce them specifically.

　　The main treatment method during pregnancy is

　　Regular prenatal examinations are important. Multiple pregnancy is a high-risk pregnancy, and the outcome of the mother and child is closely related to prenatal care. Once diagnosed, proper care and management should be done, nutrition should be strengthened, and sufficient protein, iron, vitamins, folic acid, calcium, etc. should be supplemented. Try to avoid overexertion. After 30 weeks of pregnancy, more bed rest should be taken, and active prevention of pregnancy complications and the occurrence of premature delivery should be avoided. Ultrasound monitoring of fetal intrauterine growth and development should be carried out.

　　If one of the fetuses dies in the early stage of pregnancy, the dead fetus can be completely absorbed. If the fetus dies at 3 months of pregnancy, it can be compressed into a paper-like fetus and does not require treatment; if the fetus dies in the late stage of pregnancy, it usually does not cause maternal damage, but if there is a small amount of thrombin released into the maternal body, it can cause intravascular coagulation, and the maternal coagulation function should be monitored.

　　The polyhydramnios syndrome is divided into five stages according to ultrasound diagnosis. Stage I can adopt dynamic observation, and stage II-IV can adopt selective feticide, fetal镜下胎盘血管交通支凝固术, umbilical cord blood coagulation or ligation, amniotic fluid reduction surgery, amniotic septum ostomy, etc. Fetal镜下激光阻断胎盘血管交通支 is recognized as an effective treatment method. However, attention should also be paid to the complications related to fetal intracavity treatment.

　　The main treatment method during the delivery period is

　　Multiple pregnancy can often be delivered vaginally, and it is necessary to prepare blood transfusion, intravenous fluid therapy, and emergency equipment for the rescue of pregnant women, and to master the techniques of neonatal resuscitation and resuscitation.

　　1. Indications for Termination of Pregnancy

　　①Combined with acute polyhydramnios, causing symptoms of compression, such as dyspnea, severe discomfort, etc.

　　②Maternal complications, such as preeclampsia or eclampsia, do not allow continued pregnancy.

　　③Fetal malformation.

　　④Reached the due date without labor, the placental function gradually declines or amniotic fluid decreases.

　　2. Mode of Delivery

　　Considering factors such as the age of the pregnant woman, parity, gestational age, fetal presentation, history of infertility, and obstetric complications/complications, vaginal trial of labor is generally recommended, and the indications for cesarean section are appropriately relaxed.

　　(1) Vaginal Trial of Labor

　　Choose multiple fetuses with cephalic presentation or the first fetus in cephalic presentation and the second fetus in breech presentation. The total weight of the two fetuses is between 5000g and 5500g, and the estimated weight of the second fetus is not more than 200-300g more than the first fetus.

　　(2) Indications for Cesarean Section Delivery

　　①Abnormal presentation of the fetus, such as the first fetus in shoulder presentation or breech presentation.

　　②Uterine contraction weakness leading to prolonged labor, with poor effect after treatment.

　　③Fetal distress that cannot be delivered vaginally in a short period of time.

　　④Severe complications that require immediate termination of pregnancy, such as preeclampsia, placental abruption, or cord prolapse.

　　⑤Fusion anomalies that cannot be delivered vaginally.

　　3. Treatment During Labor

　　During labor, pay attention to uterine contractions, labor progress, and fetal heart rate changes. If uterine contractions are weak, low-dose oxytocin can be administered slowly. After the first baby is delivered, immediately clamp the umbilical cord on the placental side to prevent blood loss from the second baby. At the same time, the assistant will fix the second baby in a longitudinal position on the abdomen and listen to the fetal heart rate. If there is no vaginal bleeding and the fetal heart rate is normal, wait for natural childbirth, which usually takes about 20 minutes for the second baby to be delivered. If there is still no uterine contraction after waiting for 10 minutes, artificial membrane rupture or low-dose oxytocin infusion can be administered to promote uterine contraction. If cord prolapse or suspected placental abruption or abnormal fetal heart rate is found, immediately use forceps or breech extraction to deliver the baby as soon as possible.

　　4. Prevention and Treatment of Postpartum Hemorrhage

　　During labor, open a venous access, prepare for intravenous infusion and blood transfusion. After the second baby is delivered, immediately give oxytocin to promote uterine contraction. After delivery, closely observe the uterine contraction and the amount of vaginal bleeding, especially the delayed bleeding within 2-4 hours after delivery. Antibiotics may be used to prevent infection if necessary.