1, the application of antibacterial drugs in pregnant women during pregnancy, the mother in addition to maintaining their own needs, but also to supply the needs of fetal growth and development, and to prepare for delivery. Therefore, a series of anatomical and physiological changes have to occur in all organs of the body, increasing the chances of bacterial infection. Antimicrobial drugs are one of the common drugs used during pregnancy. When choosing antimicrobial drugs, attention should be paid to the effects of the drugs on both the mother and the fetus, and the drugs should be reasonably applied according to the pharmacological characteristics of the pregnant woman and the fetus. (1) Changes in pharmacokinetics of pregnant women According to the physiological characteristics of pregnant women, the absorption, distribution, elimination and metabolic processes of drugs in the body are changed to a certain extent, especially the distribution and elimination processes have a greater impact. ① Absorption process During pregnancy, gastric acid secretion decreases, gastrointestinal peristalsis slows down, intestinal tension decreases, and the rate of gastrointestinal elimination slows down, so the absorption of oral drugs may be reduced, delayed and the peak blood concentration reduced, but the final bioavailability achieved does not change much, so the effect of absorption process is not too important. ② Distribution process Pregnant women have increased plasma volume, 40%-50% more than before pregnancy, and reduced plasma protein amount, and the blood concentration is lower than normal per capita under the condition of using common dose. In particular, when gentamicin is applied to women who have delivered by caesarean section, the blood concentration can be about 50% lower than that of non-pregnant women at the same dose. Therefore, the dose of the drug should be increased appropriately according to the situation. During pregnancy, blood volume and metabolism increase, blood flow increases, renal blood flow and glomerular filtration rate increase by 30%-50% compared with pre-pregnancy, and creatinine clearance increases, so that the elimination of gentamicin, butanamycin, etc. and most penicillins and cephalosporins, which are mainly excreted through the kidneys, is accelerated and blood concentration is reduced. The dose of these drugs should be slightly higher than the usual dose according to the situation. However, in patients with nephropathy of pregnancy toxemia, the elimination half-life of the drugs may be prolonged and the accumulation of drugs in the body should be noted. ④ Metabolic process During pregnancy, due to physiological changes liver load increases, the application of certain drugs are prone to liver damage, when tetracycline reaches more than 2g per day, serious steatosis can occur and lead to death: the incidence of liver damage is significantly higher when erythromycin is applied to pregnant women. The incidence of serum aminotransferase elevation can be up to 9.9% when pregnant women take it for more than 3 weeks, and the incidence of subclinical reversible hepatotoxicity can be up to 10-15%. Therefore, the above-mentioned hepatotoxic antibacterial drugs should be avoided during pregnancy. (2) The effect of antibacterial drugs on the fetus Some of the more toxic antibacterial drugs can enter the fetal circulation through the placenta, making the fetus an indirect drug victim. Therefore, the reasonable choice of antimicrobial drugs during pregnancy is an important issue related to the safety and health of the fetus. The effects of antimicrobial drugs on the fetus are divided into the following categories: ① Absolutely contraindicated antibacterial drugs during pregnancy is prohibited tetracycline antibiotics, because tetracycline easy through the placental barrier into the fetal body tissues, and calcium complexes synthesis complexes, deposited in the fetal whole body bones, and persist, so that delayed bone development, as well as the formation of milk teeth yellow staining, enamel development and abnormal formation of milk teeth. In animal tests. Tetracycline can cause limb deformities. Liver and kidney damage and increased stillbirths. Therefore, tetracycline antibiotics are prohibited for pregnant women: sulfa drugs are prohibited in the second trimester, because the use of sulfa in the second trimester can displace bilirubin from plasma proteins in newborns, increasing the concentration of free bilirubin, jaundice and nuclear jaundice. Methotrexate and etanercept should not be used in early pregnancy because they can inhibit folic acid metabolism and can be teratogenic. During pregnancy, especially near delivery, chloramphenicol is prohibited, because chloramphenicol can quickly penetrate the placenta, a short time to reach a peak in the fetal liver concentration is high, toxic to the hematopoietic system, can cause aplastic anemia, hemolytic anemia, more serious is caused by premature babies, neonatal “gray baby syndrome”. Gray mold is prohibited during pregnancy, because it can cause malformation or miscarriage when taken during pregnancy. ② relatively dangerous antibacterial drugs such as these mainly refers to the fetus has a certain impact, should be avoided in pregnancy, but when there are absolute clinical indications can be fully weighed the pros and cons to apply. These drugs include aminoglycosides, including gentamicin, kanamycin, streptomycin, tobramycin, butamycin, and neomycin. These aminoglycoside antibiotics can pass the placental barrier, and the concentration in the amniotic fluid is about 30%-60% of the maternal blood concentration on average, and the half-life is significantly longer in the fetus than in the mother. According to relevant data, the fetal blood concentration of gentamicin is equal to the maternal blood concentration, while the amniotic fluid concentration can be slightly higher than that of the mother. Because of the lack of fetal kidney clearance, it is very easy to cause poisoning, especially when the maternal renal insufficiency, more likely to cause kidney ear damage to the fetus, so in pregnant women who already have renal impairment of this class of drugs are prohibited. In addition, aminoglycoside antibiotics have a neuromuscular blocking effect, which may cause respiratory distress in the newborn after birth when applied during the maternity period. Metronidazole and 5-fluorouracil have been shown to be mutagenic, carcinogenic and teratogenic in animals. Quinolones such as flufenoxate, ciprofloxacin, and ofloxacin act on DNA rotase, while some species can cause cartilage damage in animals, and should be avoided during pregnancy. Furazolidine and furazolidone applied in the second trimester (7-9 months) can cause hemolytic anemia in newborns lacking glucose 6-phosphate dehydrogenase and glutathione reductase in red blood cells. Rifampin is cytotoxic and can cause teratogenicity when applied during the third trimester. Polymyxins can cross the placental barrier and have destructive effects on biofilm, and are neurotoxic and nephrotoxic. Oral administration of erythromycin during pregnancy can cause elevated serum transaminases and cholestatic hepatitis in about 10% of pregnant women, which can cause damage to the fetus. Therefore, it should be avoided during pregnancy. (3) Antimicrobial drugs that can be used during pregnancy: penicillins, cephalosporins, macrolides (excluding erythromycin) and lincomycin and phosphomycin are not easily transmissible through the placenta and have no obvious toxicity or teratogenic effects, so they can be used when necessary during pregnancy.2 Application of antimicrobial drugs in breastfeeding women Most antimicrobial drugs can be secreted into breast milk through active or passive mechanisms, making the breastfed child an unintentional indirect The breastfed child may become an unintentional indirect user or victim of the drug. Therefore, it is important to be aware of the effects of drugs that may enter the breast milk of the breastfed child when administering drugs to the breastfeeding woman. The concentration of drugs entering breast milk is not only related to the dose of the drug, but also to the protein binding rate (drugs with low protein binding rate can easily enter breast milk), molecular weight (drugs with a molecular weight of 500 do not easily enter breast milk), pH (alkaline drugs can easily enter breast milk), lipid solubility and ionization (non-ionic drugs with high lipid solubility can easily enter breast milk), and the renal function of the breastfeeding woman (renal impairment can lead to an increase in the concentration of drugs in plasma and breast milk). (3) Therefore, some drugs can be used in breast milk. (3) Therefore, the concentration of some drugs in breast milk is almost equal to the plasma concentration, and the ratio of breast milk concentration to serum concentration is nearly 1.0. The concentration of some drugs in breast milk can be significantly greater than the plasma concentration, such as erythromycin, etc.: whether the drugs in breast milk can cause adverse reactions to the breastfed child is mainly related to the following factors: ① The concentration of antibacterial drugs in breast milk The concentration of antibacterial drugs in breast milk is greater than 50% of the maternal serum drug concentration Amikacin, ampicillin, carbenicillin, clindamycin, erythromycin, chloramphenicol, gentamicin, kanamycin, ramiphene, methicillin, streptomycin, sulfonamide, tetracycline, tobramycin, methicillin. Antibacterial drug milk concentration is less than 25% of the maternal serum drug concentration, generally does not produce a clinically significant are alloxycillin, aminotrans, cefazolin, cefmenoxime, cefoperazone, cefotaxime, cefoxitin, ceftazidime, cefuroxime, meloxicillin, nalidixic acid, furantoin, metronidazole, benzathiazole penicillin, penicillin G, etc.; ② infant drinking milk: drinking milk to absorb a large amount of drugs correspondingly more. ③ infant’s clearance ability: neonatal organism is not fully developed, poor metabolism and excretion of antibacterial drugs, prone to adverse reactions; ④ pharmacological effects: different antibacterial drugs have their own pharmacological effects, drugs that are easily transferred from the blood to the breast milk, and at the same time easily absorbed through the intestinal tract of the breast, prone to adverse reactions. The antimicrobial drugs that are commonly excreted in breast milk and can cause damage to the breast are tetracycline, the intake of which can cause damage to the breast teeth. The amount of sulfonamide in breast milk can be equivalent to 1/3 of the amount taken by the infant in 24 h. This amount can lead to nuclear jaundice. If the infant lacks glucose-6-phosphate dehydrogenase, it is abnormally sensitive to sulfonamides, chloramphenicol and furans in breast milk, which can cause hemolytic anemia. Metronidazole, quinolones breast milk content with bone dysplasia may. Erythromycin intravenous drip when the milk drug concentration is 4-5 times higher than the mother’s blood concentration. Streptomycin, kanamycin, especially in the mothers with renal impairment, milk drug concentration can increase 25 times, can cause renal damage to the breast, to ensure the health of the baby, mothers should avoid the application of the above antibacterial drugs, such as the condition requires the use, should stop breastfeeding. Penicillin and cephalosporins are safer for infants, so they can be used, but attention should be paid to allergic reactions.