Many pregnant women require emergency treatment for complications, especially surgical emergencies, and often involve imaging procedures, including ultrasound, x-ray imaging and computed tomography and magnetic resonance imaging. Often medical personnel, patients and families are very concerned or worried about the safety of these physical radiations to the fetus. Therefore, it is necessary to establish a standard and effective cognitive system for imaging during pregnancy to help both doctors and patients properly understand the true risks of imaging during pregnancy and the benefits it may provide for clinical diagnostic management, which is essential for the rational use of imaging during pregnancy. I. Ultrasound Over the past 30 years, ultrasound has become an essential tool in obstetrics. Ultrasound is a form of energy, and studies have shown that ultrasound can adversely affect the neurological, immunological, hematological, developmental and genetic aspects of animal fetuses. 2009 Torloni et al. conducted a meta-analysis of 41 studies on fetal growth and development after ultrasound exposure during human gestation and showed that ultrasound exposure during pregnancy was associated with adverse maternal or perinatal outcomes, childhood disability or neurodevelopmental abnormalities, childhood malignancies, childhood intellectual abnormalities, or psychiatric morbidity were not associated with each other. The available evidence suggests that ultrasound during pregnancy is safe (Level B evidence). II. radiological imaging Some women have already received X-rays for some reason, such as a physical examination, before a pregnancy has been confirmed, while others require radiological examination to determine clinical management due to complications during pregnancy, such as suspected influenza A (H1N1) virus infection or surgical emergency abdomen. At this point, objective scientific evidence is needed to analyze the need for these examinations and their pros and cons. (i) Effects of radiation on fetal growth and development Most information on radiation-induced damage to human embryos comes from studies of the offspring of survivors of the atomic bombings in Hiroshima and Nagasaki, Japan. This group was exposed to large doses of radiation in utero, and the resulting effects fall into four main categories: spontaneous abortion, teratogenicity, carcinogenicity, and mutation induction. The estimated average absorbed dose to the fetus during various radiological imaging examinations is shown in Table 1. Therefore, the analysis of the effects of radiation on the fetus during pregnancy should be combined with the timing of exposure and absorbed dose. The absorbed dose of the organism to X-ray radiation is measured in rads (rad) 1. spontaneous abortion: embryos less than 2 weeks old (after fertilization) may be at risk of blastocyst implantation failure after receiving a radiation dose of 10 rad; however, this risk does not increase if the embryo survives. 2. Malformations: The main fetal malformations caused by high doses of X-rays are central nervous system abnormalities, especially microcephaly and mental retardation. Many survivors of the atomic bombings in Japan during World War II had microcephaly in their offspring after intrauterine exposure to the absorbed dose. Of course, this dose far exceeds the amount of radiation absorbed during an ordinary radiological examination, but it still suggests potential damage to the fetus from X-rays. Fetuses between 4 and 22 weeks of menopause are most susceptible to malformations (microcephaly, microphthalmia, mental retardation, developmental delays, and behavioral defects) from ionizing radiation, and this teratogenic effect is completely different from that of embryos before 2 weeks of embryonic age and fetuses after 20 weeks. If the absorbed dose after radiation does not exceed the teratogenic threshold, the risk of fetal malformation is not significantly increased (level B evidence). The lowest absorbed dose that can produce teratogenic effects is not well known. Therefore, non-essential radiological examinations should be performed with caution or postponed from 2 to 20 weeks after fertilization. The first case of childhood malignancy induced after intrauterine radiation was reported in 1956, but this correlation was not widely recognized until the early 1960s. It is generally accepted that the background risk of lethal malignancies in children (i.e., general population) has an incidence of 5/10,000, while the relative risk of developing childhood malignancies after intrauterine exposure to radiation doses is 2. The Oxford University Childhood Cancer Study showed that the relative risk of developing cancer in fetuses exposed to radiation in early, middle, and late pregnancy was 3.19, 1.29, and 1.30, respectively, suggesting that early pregnancy The carcinogenic risk after exposure is significantly higher than that of those exposed during mid- and late-pregnancy. The 2004 guidelines of the American College of Obstetricians and Gynecologists do not specify what information or risk estimates should be provided to patients when they inquire about the risk of radiation cancer during pregnancy, but merely describe the event as “very small” and do not recommend termination of pregnancy. (ii) Use of iodine enhancers during pregnancy In vivo studies in animals have not shown teratogenic effects of iodine-containing contrast agents during pregnancy. Studies have confirmed that in human amniotic fluid fetal imaging, direct injection of iodine-containing ionized contrast into the amniotic cavity may cause neonatal hypothyroidism, whereas intravenous injection of nonionic contrast does not affect neonatal thyroid function. The American College of Radiology guidelines state that there is no definitive conclusion on the risks of intravenous iodine-containing contrast in human pregnancy and recommend that it be used only when absolutely necessary and after informed consent has been obtained from the patient. The most recent Food and Drug Administration (FDA) guidelines require MRI instruments to be labeled as “No safety assessment has been established” for fetal MRI examinations. Fetal safety concerns relate to both teratogenic and acoustic damage. 1. Teratogenicity: No relevant research data in humans have been seen to show that maternal exposure to MRI magnetic fields below Dessla) can have long term effects on the offspring. Although animal studies have shown no effect on fetal development in pregnant rats after continuous exposure to 4 tesla magnetic fields on day 9 of gestation, a few studies have suggested that exposure to magnetic fields during early pregnancy may have teratogenic effects on the animal fetus, with possible teratogenic mechanisms including thermal effects from changes in magnetic resonance gradients and non-thermal effects from biologically structured electromagnetic field interactions. Although the results of animal studies are not necessarily applicable to humans, caution is needed for fetal MRI examinations in early pregnancy in humans. 1991 guidelines from the National Radiological Protection Agency (NRP) in the UK state that MRI examinations should not be performed in early pregnancy. Because early pregnancy is a time of high incidence of spontaneous abortion, if spontaneous abortion occurs after an MRI examination, the patient may mistakenly believe that it is due to MRI. In clinical practice, MRI in early pregnancy is usually required for maternal pathology rather than for prenatal fetal diagnosis, so MRI should only be chosen when it is relevant to clinical management decisions in early pregnancy. The 2007 U.S. radiation safety guidelines state that “MRI can be used safely at any time during pregnancy as long as the patient accepts the risks and benefits of MRI”. 2. Hearing impairment: Although MRI scanner coils can produce high frequency noise, clinical and experimental evidence suggests that the risk of fetal hearing impairment is negligible after MRI examinations. 3, the use of contrast enhancers in MRI examinations: animal experiments have shown that high doses and repeated intravenous injections of gadolinium have teratogenic effects. Gadolinium can pass through the placenta and is presumed to be excreted via the fetal kidney into the amniotic fluid. The 2007 U.S. Radiation Safety Guidelines recommend that intravenous gadolinium should be avoided during pregnancy for the safe use of MRI and should only be considered when absolutely necessary. It should be considered only when absolutely necessary. In addition, pregnant women must be informed of the advantages and disadvantages of using gadolinium and must give their informed consent. 1. Suspected acute appendicitis: The clinical diagnosis of appendicitis in pregnancy is sometimes very difficult, and ultrasound, CT and MRI can be used for the imaging diagnosis of suspected appendicitis. In a study including 42 cases of suspected appendicitis in pregnancy, the sensitivity of ultrasound diagnosis was up to 100%, the specificity 96%, and the accuracy 98%. Another study suggested that the accuracy of CT in the diagnosis of appendicitis in pregnancy was up to 100%. Currently, ultrasound is considered to be the preferred test, and if the ultrasound result is negative, further CT examinations should be performed. In recent years, MRI has become a valuable diagnostic tool due to the absence of radioactivity. 51 cases of pregnant women with clinically suspected appendicitis were examined by MRI, which showed that the overall sensitivity of MRI in diagnosing acute appendicitis during pregnancy was 100% and the specificity was 93.6%. 2, suspected influenza A (H1N1): pregnant women are at high risk of attack by influenza A (H1N1) virus, with a higher rate of death than the general population. The virus mainly involves the lungs, the appropriate application of imaging means for the early identification of severe / critical illness is very important. mollura et al. study shows that the fatal H1N1 influenza virus infection of the chest radiographs and CT scans have specific performance: radiographs can show the lungs around the lamellar shadow, CT shows the lungs around the hairy glass-like cloudy shadow, these imaging tests are indicative of the presence of bronchial Peripheral injury. Even if the nasopharyngeal swab H1N1 virus rapid antigen test is negative, these imaging manifestations still suggest H1N1 virus infection. Therefore, the majority of scholars believe that CT is the general population or pregnant women suspected and confirmed cases of the preferred chest examination program. 3, suspected renal colic: the incidence of pregnancy combined with obstructive urinary stones is about 1/3300, ultrasound can detect 60% of urinary stones and is the preferred test. If the ultrasound result is negative, other imaging tests such as non-enhanced spiral CT or intravenous pyelogram should be considered. 4. Trauma: In most cases, fetal heart monitoring and ultrasound are sufficient to assess the condition of trauma during pregnancy, but CT should be performed when clinical or ultrasound suggests visceral injury with intra-abdominal hemorrhage. For those whose vital signs are unstable after trauma, MRI examination is time-consuming, so it is not suitable for urgent and critical cases. 5. Suspected pulmonary embolism: Pregnancy-related pulmonary embolism mostly occurs in postpartum patients with preterm labor, cesarean delivery and multiple pregnancies. In all trimesters, the absorbed X-ray dose of fetal exposure from CT pulmonary angiography is much lower than the dose from ventilation and perfusion imaging, so it is the imaging technique of choice for suspected pulmonary embolism during pregnancy. Table 2 lists the current consensus opinions of international mainstream academic institutions on imaging during pregnancy. The maximum cumulative absorbed safe dose that the fetus can receive should not exceed 5 rad. Patient-physician communication on imaging during pregnancy 1. Is it safe for my child?”. The clinician must answer this question. When answering this question, the clinician must choose the language carefully to help the pregnant woman understand that the real risk is actually small, but should also make her aware that even if the risk is small, it is still increased. For example, the total risk of spontaneous abortion, malformations, mental retardation, and childhood malignancies in the general population is approximately 286/1000, and if the fetus receives an amount of radiation, the adverse effects increase by only 0.17/1000 from the background risk, or only one radiation-induced adverse outcome per 6000 fetuses exposed to radiation. However, if these data are listed to patients, the only words that pregnant women may hear are “risk”, “miscarriage”, “mental retardation” and “childhood malignancy,” to name a few, presenting a challenge for physicians to communicate well during patient counseling. The term “safe” is relative, but clinicians need not shy away from using it. If a pregnant woman needs radiological imaging, the ACR recommends that “medical personnel should inform the patient that X-rays are relatively safe and clearly communicate the need for and benefits of X-rays to the patient, and let the patient know that the absorbed dose for a single examination is well below the safety threshold. Understanding of background risks: Clinicians help patients understand the existence of background risks as an essential part of safety counseling, meaning that birth defects can occur naturally in the general population of pregnant women even in the absence of any causal factors. The current natural incidence of fetal malformations in the general population is approximately 4 to 6 percent, so physicians can never promise that a fetus will not develop any birth defects. The amount of fetal uptake after a single X-ray is unlikely to cause fetal damage, but if an abnormality occurs in a fetus born after a radiograph, parents often blame the abnormality on the radiological examination, making it difficult to accept the idea that there is a background risk of fetal malformation itself, which may lead to medical disputes. Therefore, the doctor’s consultation must be complete, scientific and logical. It should also be recorded objectively in the medical record. 3. Reasonable reminders: Diagnostic X-ray examinations during pregnancy are generally considered safe, and clinicians should give appropriate reminders in the face of patients’ anxiety. Good communication can increase mutual trust between the doctor and the patient. Therefore, the indication for the test, the means of the test, and the possible consequences must be drawn up in the record and the patient’s fully informed consent must be obtained. 4. Counseling for termination of pregnancy: Hammer-Jacobsen proposed the “Danishrule” in 1959, which recommends termination of pregnancy if the fetus absorbs more than the dose of radiation. To date, no study has justified termination of pregnancy on the basis of radiation dose from a single clinical radiological examination. In clinical practice, some pregnant women may inappropriately choose to terminate their pregnancies due to misconceptions about radiation exposure or concerns about malformations in their children. Although low-dose radiation exposure may increase the chance of childhood leukemia, termination of pregnancy as a means of preventing leukemia would require the abortion of 1999 exposed fetuses to prevent 1 case of leukemia. Therefore, the ACOG guidelines clearly state that “X-ray exposure during pregnancy is not an indication for therapeutic abortion”. In counseling pregnant women who have been exposed to X-rays or patients who have been unintentionally exposed to radiation and have not yet determined whether they are pregnant, obstetricians should provide patients with an objective assessment of the degree of risk to the fetus from the absorbed dose of radiation in an objective and scientific manner to help patients make a well-informed choice about whether to continue with their pregnancy. VII. Summary The complication of certain diseases in pregnant women can cause serious adverse effects on the mother and child that go well beyond the potential risks associated with low-dose radiological examinations. Clinicians should not hesitate to recommend radiological testing if it is directly related to the patient’s further diagnosis and treatment. However, non-emergency x-ray examinations at 2 to 20 weeks after fertilization should be avoided as much as possible because this is the most sensitive period for the development of the fetal central nervous system. It is the responsibility of the medical staff to give proper and objective counseling to the patient before performing radiological examinations. Good communication helps to reduce patient anxiety and correct misconceptions, reducing doctor-patient disputes. Ultrasonography is considered safe throughout pregnancy and should be the preferred modality for imaging during pregnancy.