The discovery of syphilis during pregnancy can be a worrying event. How does syphilis affect the pregnant woman and the fetus? How should it be treated? All are of great concern. I will now answer common questions about syphilis in pregnancy as follows. The purpose of syphilis treatment during pregnancy: In early pregnancy, treatment is to keep the fetus free from infection: in late pregnancy, treatment is to cure the infected fetus before delivery and to treat the pregnant woman as well. All pregnant women newly diagnosed with syphilis during pregnancy should be treated according to the appropriate syphilis staging. What medications can be used to treat syphilis in pregnancy? The principles of treatment are the same as for non-pregnant patients, except that tetracycline and doxycycline are prohibited and a quantitative non-syphilis spirochete serological test is done once a month after treatment to observe for recurrence and reinfection. A course of anti-syphilis treatment was given to patients with syphilis during pregnancy in the early 3 months of pregnancy and the last 3 months of pregnancy. For those who are allergic to penicillin and cephalosporins, since tetracyclines cannot be used during pregnancy and lactation, they can only be replaced by macrolides, e.g. erythromycin 500 mg, 4 times a day, for 15 days for early syphilis and 30 days for late syphilis and syphilis of unknown stage. It is important to note that erythromycin has poor efficacy in the treatment of syphilis and that clinical and serological follow-up should be intensified after treatment. After cessation of breastfeeding, retreatment with doxycycline is indicated. Erythromycin does not cross the placenta and has no therapeutic effect on the fetus. How soon after treatment of syphilis in pregnancy should I be retested? After early syphilis treatment, the syphilis seropositivity should be checked once a month before delivery, and if the seropositivity titer does not drop by 2 dilutions within 3 months, the treatment should be repeated. After delivery, follow up should be done according to general syphilis cases. What are the possible effects of syphilis in pregnancy on the fetus? Because syphilis in pregnancy may cause fetal infection through the cord blood, miscarriage, stillbirth, and some fetal syphilis may occur. Therefore, pregnant women with syphilis in pregnancy should be followed up once a month with an ultrasound examination. The placenta, amniotic fluid and fetal development should be observed. How is the fetus of a pregnant woman with syphilis who has been adequately treated treated handled and followed up? When the baby is born, if the non-syphilis spirochete serological test and syphilis spirochete serological test are positive, it should be rechecked every 3 months; at 6 months, if it is negative and there is no clinical manifestation of fetal syphilis, fetal syphilis can generally be excluded. Syphilis spirochete serologic reactions generally turn negative 15 months after birth and are the main basis for retrospective diagnosis of fetal syphilis if they are still positive at 18 months of age. Infants born with negative non-syphilis spirochete serologic test and syphilis spirochete serologic test reactions should be reviewed at 1, 2, 3 and 6 months after birth, and syphilis can be excluded if they are still negative by 6 months of age and have no clinical manifestations of fetal syphilis. A gradual increase in titer during the follow-up period or the appearance of clinical signs of fetal syphilis should be treated immediately. Infants who are not eligible for follow-up may be treated for prophylactic syphilis. The prophylactic treatment regimen for infants is benzathine penicillin, 50,000 U/kg, 1 injection. Infants born with a non-spirochete serologic test titer greater than or equal to four times that of the mother or with clinical signs of fetal syphilis (regardless of syphilis serologic test results) should be treated for fetal syphilis and followed closely. How is the fetus of an untreated pregnant woman with syphilis managed and followed up? Infants born to pregnant women with syphilis who are not adequately treated or treated late in pregnancy or not treated with penicillin should be given prophylactic syphilis treatment and followed up if they have a negative non-syphilis spirochete serologic test, or if they are positive but have a titer less than four times that of the mother. However, if there are manifestations of fetal syphilis, they should be treated as fetal syphilis. Regardless of whether there are manifestations of fetal syphilis or not, their non-syphilis spirochete serologic test titer is greater than or equal to 4 times that of the mother, they should be treated as congenital syphilis and followed up.