Abdominal pregnancy

　　1. Etiology

　　Primary abdominal pregnancy is very rare, and the cause of its occurrence is unknown. However, some scholars believe that the peritoneal epithelium may transform into mesonephric tubular epithelium, especially when there is ectopic endometrium in the peritoneum or pelvis, which allows the fertilized egg to implant and develop into primary abdominal pregnancy.

　　Secondary abdominal pregnancy mostly occurs in the rupture or post-abortion fallopian tube pregnancy, where the pregnancy material comes from the rupture or fimbriae, but part of it still adheres to the affected area. The villi of the implantation site survive and adhere to the nearby peritoneum or organs, continuing to develop into abdominal pregnancy. A few cases occur after the rupture of ectopic ovarian pregnancy, and for those who have had cesarean sections and become pregnant again, the cesarean section incision may rupture, with the fetus wandering outside to the abdominal cavity, or other causes of uterine incisions, uterine abdominal fistula, etc., which can also lead to rare abdominal pregnancy. Due to the different attachment site of the placenta in abdominal pregnancy from that in the normal uterus, the blood supply is very poor, and therefore the fetus also develops poorly, with only 5% to 10% surviving to full term. The rest die in the abdominal cavity at different gestational ages, with their soft tissues absorbed and bones remaining, or mummified and petrified. There are also cases of secondary infection forming abscesses,溃破 into surrounding tissues, such as the umbilical cord of the mother, intestines, vagina, etc., resulting in the excretion of fetal hair and bone fragments, which are quite helpful for diagnosis.

　　Second, pathogenesis

　　There are two factors that promote the primary implantation of the ovum in the peritoneum:

　　1. The coelomic epithelium has the ability to transform and can develop into tissue similar to the paramesonephric duct epithelium. The decidual reaction on the posterior abdominal wall of the uterus is often considered as evidence of the possibility of transformation of the coelomic epithelium;

　　2. The implantation of endometrium on the peritoneal surface is conducive to the implantation of the ovum.

　　Secondary abdominal pregnancy is more common than primary abdominal pregnancy. It refers to tubal pregnancy abortion or rupture, where the gestational fluid flows into the abdominal cavity, implants on the surface of the peritoneum or other organs, or continues to grow and develop in the abdominal cavity with blood supply without completely detaching from the fallopian tube. Secondary abdominal pregnancy can also occur secondary to pregnancy within the ovary or uterus. Natural rupture, such as spontaneous rupture or uterine peritoneal fistula due to defects in the uterus (such as cesarean section, cesarean section for fetal extraction, and uterine fibroid resection scar), or uterine diverticulum or underdeveloped primordial uterus, etc., can lead to the gestational material being squeezed into the abdominal cavity through the orifice or fistula. It continues to grow and develop into abdominal pregnancy.

　　It can be complicated by infection, fever, abdominal abscess, and peritonitis.

　　An abdominal abscess refers to the localized accumulation of pus in a certain space or location within the abdominal cavity, which is caused by tissue necrosis and liquefaction, and is wrapped by intestinal loops, visceral organs, abdominal wall, omentum, or mesentery, etc. It includes subdiaphragmatic abscess, pelvic abscess, and interintestinal abscess.

　　Peritonitis is the inflammation of the parietal peritoneum and visceral peritoneum of the abdominal cavity, which can be caused by bacterial, chemical, and physical injuries, and can be divided into primary peritonitis and secondary peritonitis according to the pathogenesis. Acute purulent peritonitis involving the entire abdominal cavity is called acute diffuse peritonitis.

　　In recent years, the incidence of ectopic pregnancy has shown an increasing trend. This is an important issue facing us. Although the exact etiology of the disease is not yet fully clear, many factors related to it are very clear. Reducing its high-risk factors can achieve the purpose of prevention.

　　1. Strengthen the publicity and social governance of the prevention and treatment of sexually transmitted diseases.

　　1. When placing an intrauterine contraceptive device or performing other intrauterine procedures such as induced abortion, strict adherence to operational procedures and infection prevention measures is crucial.

　　2. In the case of pelvic soft tissue infection, it should be treated early, and a complete cure should be achieved in one session.

　　3. Actively treat endometriosis.

　　4. After using ovulation-inducing drugs, if early pregnancy is suspected or assisted conception is successful, it is necessary to timely exclude ectopic pregnancy and twin pregnancy.

　　5. Publicize the hazards of smoking and prohibit drug abuse.

　　The diet of patients with intra-abdominal pregnancy should be light and easy to digest, with an emphasis on eating more vegetables and fruits, and a reasonable diet should be balanced. In addition, patients should also pay attention to avoiding spicy, greasy, and cold foods.

　   1. Treatment

　　The management of intra-abdominal pregnancy is relatively complex. Due to the accumulation of experience and the improvement of surgical methods, Stevens et al. (1993) reported that the maternal mortality rate has decreased from 20% to 5% in the past 20 years.

　　The presence of intra-abdominal pregnancy can lead to infection, abscesses, and sinus tracts. Therefore, once the diagnosis is confirmed, surgical treatment should be considered. The main key to surgery is the management of the placenta, as improper management can result in excessive bleeding at the placental attachment site and organ damage. Therefore, the method of management should be decided based on the placental attachment site, whether the fetus is dead, and the duration of death.

　　If the fetus located in the abdominal cavity is not removed by surgery, the following situations may occur: ①Residual fetal bones, absorption of soft tissue; ②Formation of adipocere; ③Formation of stone fetus or calcification; ④Infection, necrosis, and abscess formation of fetal tissue; ⑤If the fetal tissue remains in the abdominal cavity for a long time, it may penetrate into the bladder and rectum, forming abdominal fistulas and other conditions.

　　Some authors advocate the use of methotrexate to destroy the remaining placenta. The mechanism of action is that methotrexate can destroy the trophoblastic tissue, reduce the blood supply of the placenta, promote its degeneration and necrosis, and HCG can be reduced to normal levels. The disadvantages of using methotrexate are that the destroyed placental tissue left in the abdominal cavity is a good culture medium for bacteria, and there is a possibility of concurrent infection, leading to peritonitis, abdominal wall wound dehiscence, pelvic abscess, sepsis, and even death in severe cases. In cases where methotrexate is not used, although the absorption of the placenta is slower, the recovery period of the patient is delayed, but the complications are fewer.

　　1. Blood transfusion must be prepared before surgery, and intestinal preparation must be done well.

　　2. If the fetus is alive or has died recently, remove the fetus, tie and cut the umbilical cord at the attachment site of the umbilical cord on the placental surface, and leave the placenta in the abdominal cavity. At this time, the placental implantation area is closely adhered to the abdominal organs or tissues, with rich blood sinusoids, and bleeding can occur during separation. The retained placenta may be organically absorbed. If it is not absorbed, consider the surgical treatment plan in the future.

　　3. If the fetus has been dead for a long time, such as for several weeks or several months, and the placental implantation area is not large, the placenta has atrophied, and most of the blood sinusoids have closed, it can be tried to remove the entire placenta. Generally, there is not much bleeding.

　　4. If the placenta is planted on the omentum, the omentum can be removed along with it, but if it is planted in the pelvic cavity, it is strictly forbidden to forcibly remove it, as the bleeding is difficult to control. There have been reports that scholars who plant the placenta at the pelvic floor first perform percutaneous femoral artery pelvic angiography and then perform internal iliac artery embolization, followed by surgery to significantly reduce the amount of bleeding. If massive bleeding occurs during surgery, this method can also be used to stop bleeding.

　　In recent years, there have been reports that placental retention during surgery has caused infection, abscess, poor wound healing, and intestinal obstruction. There have also been reports of maternal pyelonephritis and even persistent preeclampsia for 99 days until the placenta was removed and cured. However, compared with the risk of massive hemorrhage during surgery, most scholars still hold the opinion of postoperative placental management. If the placenta is retained in the abdominal cavity, the decrease of serum β-HCG can be observed, and most of them decrease rapidly, but Belfar et al. (1986) reported that the absorption time of the placenta can last up to 5 years.

　　II. Prognosis

　　Abdominal pregnancy is rare, but sometimes serious, with a maternal mortality rate of about 10%, a fetal mortality rate of about 50%, and a fetal malformation rate of about 20%.