A 24-year-old woman, gravida 1 para 0, at 28 weeks gestation comes to the office for a routine prenatal visit. She reports active fetal movement and has had no vaginal bleeding, leakage of fluid, or contractions. The patient has no chronic medical conditions and has had no prior surgery. She does not use tobacco, alcohol, or illicit drugs. At her initial visit in the first trimester, prenatal testing results were as follows: The patient and her partner were treated with azithromycin, and the patient had subsequent negative C trachomatis testing a month later. Blood pressure is 118/74 mm Hg and pulse is 90/min. BMI is 34 kg/m². Fundal height is 28 cm and fetal heart tones are 130/min. A 1-hour glucose challenge, complete blood count, and C trachomatis test are ordered. Which of the following additional screening tests are indicated for this patient at today's 28-week gestation prenatal visit?

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Explanation: 11ec25c8_da88_86ca_bc81_0be444c79e74_MD0003_00 At the initial prenatal visit, all patients undergo HIV, hepatitis B virus, and syphilis screening because these sexually transmitted infections (STIs) can cause congenital infection with devastating fetal consequences, and vertical transmission is typically preventable with early identification and treatment. In addition, patients with risk factors (ie, high-risk patients) also require gonorrhea and chlamydia screening because these infections can cause preterm prelabor rupture of membranes and neonatal infection (ie, conjunctivitis). These risk factors include: Age <25 Prior STI High-risk sexual activity (eg, multiple partners, commercial sex work) Because these high-risk patients have an increased risk of new STI exposure, they also require repeat screening for all STIs in the third trimester. This high-risk patient tested positive for chlamydia in the first trimester, underwent treatment, and had negative repeat testing a month later. However, she requires repeat third trimester (ie, ≥28 weeks gestation) testing for all STIs (eg, C trachomatis, rapid plasma reagin assay, HIV) due to the risk of reinfection (eg, untreated or undertreated partner). (Choice A) Cervicovaginal fetal fibronectin (fFN) is secreted during labor and helps distinguish between preterm and false labor in patients with preterm contractions. However, asymptomatic patients such as this one do not undergo fFN testing due to high false-positive rates. (Choice B) Group B Streptococcus rectovaginal culture is typically collected at 36-38 weeks gestation (ie, near anticipated delivery) to identify patients at risk for neonatal transmission. Earlier testing is indicated in patients with risk factors for early delivery (eg, preterm labor, multiple gestation). (Choice D) An ultrasound for cervical length assesses the risk of preterm delivery in patients with preterm contractions, prior preterm delivery, or a shortened cervix identified on prior ultrasound. It is not typically performed in the third trimester due to normal cervical shortening. Educational objective: Sexually transmitted infections (STIs) in pregnancy can cause obstetric and fetal complications (eg, preterm prelabor rupture of membranes, congenital infection). Therefore, all patients undergo STI screening at the initial prenatal visit, and high-risk patients (eg, age <25, prior STI) require repeat screening in the third trimester. References: Sexually transmitted infections: recommendations from the U.S. Preventive Services Task Force. (http://www.ncbi.nlm.nih.gov/pubmed/27929270) Screening for syphilis infection in pregnant women: U.S. Preventive Services Task Force reaffirmation recommendation statement. (http://www.ncbi.nlm.nih.gov/pubmed/30193283)

A 24-Year-Old Woman, Gravida 1 Para 0, at 28 Weeks