Do you have to terminate pregnancy after X-ray or CT during pregnancy?

Do you have to terminate pregnancy after X-ray or CT during pregnancy?

Do you have to terminate pregnancy after X-ray or CT during pregnancy? Everyone's physique is different. Some people vomit during pregnancy, and some people can't do some radiological examinations. Very strange! Actually, it's common sense. Do you have to terminate pregnancy after X-ray or CT during pregnancy?

Do you have to terminate pregnancy after X-ray or CT during pregnancy? 1 Real case: renal colic during pregnancy, giving up baby CT.

This is a real case: in a local hospital, a pregnant woman who was pregnant for 6 months suddenly suffered from renal colic. Kidney calculi was suspected by urology department, but no abnormality was found by B-ultrasound. The patient's low back pain was aggravated and could not be diagnosed. After discussion, CT examination is necessary. A simple examination problem has risen to the field of protecting adults or children because of the particularity of patients. Finally, out of ignorance and fear of X-ray ionizing radiation (harmful to human body when reaching a certain dose, different from the non-ionizing radiation generated by mobile phones and microwave ovens in life), patients and their families decided to have a CT scan of the abdomen and pelvis and decided to give up the baby in the belly.

As a radiologist, I have to say that this is a sad story. What is more sad is that this kind of story is often staged everywhere.

In recent decades, due to the needs of illness, pregnant women need to undergo radiation examination more and more. Statistics show that in recent ten years, radiation examination has increased by 107%, but pregnant women, their families and even medical staff do not know enough about it, and many pregnancies have been wrongly terminated!

Do pregnant women have to terminate their pregnancy as long as they take X-rays or do CT?

In fact, during most X-ray and even ct examinations after pregnancy, the uterus is not directly irradiated, and the radiation received by the fetus is very small. Because the fetus is well protected by the mother, including skin, subcutaneous fat, uterine wall, amniotic fluid and so on. For example, when doing a head CT scan, the radiation of the fetus is even zero. Of course, at this time, the abdomen must be protected with lead clothes. Let's take an extreme example. In the commonly used clinical radiology examination (excluding PET-CT), serious radiation comes from the direct irradiation of X-ray or CT in abdomen and pelvis. For example, in the story introduced at the beginning of this article, the radiation amount is relatively high, which is 25mSv (but the current CT technology can be completely lower than this value). Can I have a baby at this time?

Routine inspection of radiation dose belongs to low-risk exposure.

Usually, when diagnosing and treating a certain disease or guiding a certain medical behavior in medicine, a large number of experiments are needed to obtain enough evidence to give. However, in this case, it is impossible to carry out human experiments. However, according to a large number of clinical observations and the analysis of some nuclear radiation time in history, many countries in the world have put forward their own guiding opinions at present. For example, the National Radiation Protection and Measurement Committee of the United States has suggested that when the fetal radiation dose is less than 50mGy (which can be approximately equal to mSv), the risk can be ignored. Radiological examination for diagnostic purposes does not mean termination of pregnancy.

Note that it is 50mGy, and the abdominal and pelvic CT scan mentioned above is 25mSv, which is half of this dose. In clinical examination, almost all diagnostic X-ray examinations are lower than this value, such as taking the chest position, and the radiation dose to the fetus is 0.002mSv, which is almost negligible. Even for CT scans, most examinations are lower than this dose, such as common chest CT scans. What is the concept that the radiation dose of the fetus is only 0.2mSv? Most people who live on the earth still have to receive radiation from the universe, even if they have never set foot in the hospital. The dose is 2.4 ~ 3. 1 msv per year. Most people think that when the radiation dose received by the general population is less than 50mSv, it belongs to low-risk radiation. So unnecessary radiation, but don't be too afraid.

There is another situation, that is, I found myself pregnant in the month of X-ray or CT examination, and then many people think that the child is too fragile at this time to give birth. This idea is also wrong. In the month of pregnancy, if the X-ray or CT examination has no effect on the fetus within 30 days from the first day of the last menstruation, that is to say, either the child runs away or the child stays.

If necessary, non-ionizing radiation inspection is preferred.

Of course, during pregnancy, if necessary, imaging examinations without ionizing radiation, such as B-ultrasound and magnetic resonance imaging (MRI), should be preferred. Both have been proved to be correct for the fetus. But in some special cases, when B-ultrasound and MRI can't solve the problem, CT can be carefully selected, such as appendicitis, pulmonary embolism, renal colic and trauma. At this time, we will evaluate the radiation dose, but it must be noted that most of the doses used in clinical X-ray and ct examinations are aimed at the fetus.

Do you have to terminate pregnancy after X-ray or CT during pregnancy? Common misunderstandings and guidelines of imaging examination during pregnancy.

At present, there are often the following misunderstandings in imaging examination during pregnancy: ① Radiological examination such as X-ray during pregnancy will greatly increase the risk of miscarriage and fetal malformation, and pregnancy should be terminated; ② Never do positron emission tomography (PET)/CT examination during pregnancy, otherwise it will lead to fetal defects.

The American College of Obstetrics and Gynecology (ACOG) issued the guidelines for imaging examination during pregnancy on 20 16. The suggestions are as follows:

① Ultrasound and magnetic resonance imaging (MRI) have no risk of ionizing radiation and are relatively safe examinations during pregnancy, but they are only recommended for related clinical problems or when they bring medical benefits to patients;

② Except for a few cases, the radiation exposure dose caused by X-ray examination, CT scanning and PET/CT is far lower than that caused by fetal damage. If these examinations are necessary supplements to ultrasound or MRI, or are more conducive to disease diagnosis, they should not be rejected.

③ Only when the clinical benefits outweigh the risks, it is recommended that pregnant women use gadolinium as MRI contrast agent (that is, MRI enhancement examination).

Risk analysis of imaging examination during pregnancy

The risk of pregnancy imaging examination to fetus is related to gestational age and ionizing radiation dose (table 1). Higher doses of radiation can lead to birth defects, growth restriction and mental retardation of the fetus, among which 8~ 15 weeks of pregnancy has the greatest impact on the central nervous system. In addition, the fetus will be exposed to certain' natural background radiation' during pregnancy, and its dose is about 1mGy. High dose ionizing radiation (> > 1Gy) in early pregnancy may lead to the risk of embryo death.

X-ray examination

When the radiation exposure dose of the fetus is less than 50 Gy, no research shows that there are risks such as growth restriction, fetal malformation and abortion, and the fetal dose range of most diagnostic X-ray examinations is far below 50 Gy (Table 2). In addition, it is not clear whether intrauterine ionizing radiation is carcinogenic, but it is unlikely.

Therefore, intentionally or unintentionally taking X-rays during pregnancy, there is no need to terminate pregnancy. However, if X-ray examination is carried out many times, it is necessary to consult with radiologists and obstetricians to calculate the total radiation dose of the fetus and evaluate the possible impact on the fetus.

CT plain scan and enhanced scan

CT uses X-ray beams to scan a certain thickness of the inspection site from multiple directions. Similar to X-ray examination, the risk of CT examination is related to gestational age and radiation dose, and the radiation dose to the fetus depends on the scanning location, scanning layers and layer spacing. If pregnant women undergo head CT examination, the radiation dose to the fetus is only1.0 ~10mgy; However, if pelvic CT examination is performed, the radiation exposure dose of the fetus can be as high as 50mGy. Therefore, if pelvic CT examination is necessary, we should fully communicate with radiologists and technicians to minimize the radiation dose without affecting the examination effect.

Enhanced CT examination is often used for further diagnosis, and the commonly used contrast agent is meglumine diatrizoate (ionic monomer iodine). Meglumine diatrizoate can enter fetal tissue through placenta. If the abdomen is exposed to X-rays many times during radiography, it may have adverse effects on the fetus. However, in previous animal and human experiments, there is no clear evidence to show the specific damage of iodine contrast to the fetus. Therefore, if there are clear indications in clinic, we should not refuse to use CT plain scan plus enhanced examination, but should fully weigh the advantages and disadvantages and use it carefully.

Plain and enhanced MRI examination

There is no risk of ionizing radiation in MRI examination, and the safety of MRI plain scan is relatively certain. Gadolinium is a commonly used contrast agent in MRI enhancement examination, and the risk of its use during pregnancy is still controversial. Gadolinium is water-soluble and can enter fetal circulation and amniotic fluid through placenta. Free gadolinium is toxic. Although its chelates have been used in clinic, large and repeated doses of gadolinium still have teratogenic effects, and should only be considered if the advantages outweigh the disadvantages.

PET/CT

The radiation dose of PET/CT depends on the physical and biochemical characteristics of radioisotopes. Usually, the fetal radiation exposure dose of PET/CT examination is 10~50mGy.

But not all radioisotopes are safe to use during pregnancy. For example, 13 1I can easily cross the placenta, causing adverse effects on fetal thyroid, with a half-life of 8 days. Therefore, 13 1I should not be used for pregnancy diagnosis and treatment.

Because PET/CT has unique advantages in the diagnosis of tumor characterization and recurrence, if pregnant women have clinical indications after full evaluation, they should inform patients and their families of their illness, "choose the lesser of the two evils", choose isotopes that are less harmful to the fetus for PET/CT examination, and use them in small doses as far as possible without affecting the examination effect.

summary

We advise women to avoid unnecessary radiation exposure during pregnancy. If you really need to undergo diagnostic imaging examination, if the radiation exposure dose is less than the fetal teratogenic dose, you don't have to worry too much; If the radiation exposure dose is greater than the fetal teratogenic dose, it may directly affect the germ cells to further form embryos.