A 24-year-old woman, gravida 1 para 0, comes to the office at 12 weeks gestation for an initial prenatal visit. She is feeling well and reports no nausea, cramping, or vaginal bleeding. The patient has no chronic medical conditions and has had no previous surgeries. She takes a prenatal vitamin daily. Pap test and sexually transmitted infection screening last year were normal. Family history is not significant. She drank 1 or 2 alcoholic beverages a week prior to pregnancy, but does not use tobacco or illicit drugs. The patient developed a skin rash and difficulty breathing after taking penicillin for streptococcal pharyngitis as a child. Blood pressure is 110/60 mm Hg and pulse is 78/min. BMI is 26 kg/m². Bimanual examination is consistent with a 12-week-sized uterus. Pelvic ultrasound reveals a singleton intrauterine pregnancy consistent with gestational age. Fetal heart rate is 160/min. Laboratory results from this visit are as follows: Which of the following is the most appropriate treatment for this patient?

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Explanation: 11ec2b69_bfc2_601a_8f63_2bb2a9dd562f_MD0005_00 Treponema pallidum crosses the placenta; a syphilis infection during pregnancy can result in vertical transmission, leading to adverse fetal outcomes including fetal growth restriction, intrauterine fetal demise, and congenital syphilis (eg, hepatomegaly, jaundice, rash, skeletal abnormalities). Therefore, all pregnant patients are screened at the initial prenatal visit with either the rapid plasma reagin or the VDRL test. Repeat screening can be performed in the early third trimester for high-risk patients. Those with a positive screening test require confirmatory testing with a treponemal-specific test (eg, fluorescent treponemal antibody absorption, microhemagglutination test for antibodies to T pallidum). Penicillin is the first-line therapy for the treatment of syphilis during pregnancy as it treats maternal disease, prevents vertical transmission, and treats fetal infection. Patients who have a penicillin allergy require penicillin desensitization prior to treatment. Penicillin desensitization typically involves incremental doses of either oral or intravenous penicillin followed by treatment with intramuscular penicillin G benzathine. To ensure an adequate response following treatment completion, repeat serologic titers are obtained in the third trimester (eg, 28-32 weeks gestation) and at delivery. A 4-fold or greater decrease in the serologic titer indicates treatment success; an inadequate response requires additional treatment. (Choices A and D) Azithromycin and erythromycin are second-line antibiotics for syphilis in nonpregnant patients. Although both are safe in pregnancy, neither crosses the placenta or treats fetal infection. (Choice B) Ceftriaxone is a second-line antibiotic for nonpregnant patients with syphilis. However, it is insufficiently studied for the treatment of syphilis during pregnancy. (Choice C) Doxycycline is a second-line antibiotic for nonpregnant patients with syphilis. It is contraindicated in pregnancy due to a risk of fetal tooth staining and abnormal fetal long bone development. Educational objective: Penicillin is the first-line antibiotic for patients with syphilis during pregnancy. Patients with a penicillin allergy require penicillin desensitization prior to initiating treatment. References: Syphilis during pregnancy: a preventable threat to maternal-fetal health. (http://www.ncbi.nlm.nih.gov/pubmed/27956203) The continuing threat of syphilis in pregnancy. (http://www.ncbi.nlm.nih.gov/pubmed/26871538)

A 24-Year-Old Woman, Gravida 1 Para 0, Comes to the Office