A 34-year-old woman, gravida 3 para 2, at 12 weeks gestation comes to the office for a routine prenatal visit. The patient reports no nausea, vomiting, abdominal pain, or vaginal bleeding. The patient's 2 previous pregnancies were complicated by poorly controlled type 2 diabetes mellitus and resulted in term cesarean deliveries for fetal macrosomia. Both children are healthy. The patient has no other chronic medical conditions. She takes a prenatal vitamin daily, and her glucose levels are controlled with an insulin regimen. She does not use tobacco, alcohol, or illicit drugs. Family history is noncontributory. Blood pressure is 120/70 mm Hg and pulse is 68/min. BMI is 30 kg/m². Bedside Doppler examination reveals a fetal heart rate of 164/min. The patient requested a first-trimester combined test, and the results revealed normal-range nuchal translucency thickness, low pregnancy-associated plasma protein A, and an elevated β-hCG level. The results are discussed and the patient desires further management of these results. Which of the following is the best recommendation in management of this patient's laboratory findings?

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Explanation: 11ec2b69_c19c_9e83_8f63_63d381a3a4d5_MD0005_00 The first-trimester combined test is a screening test for aneuploidy and has a higher detection rate than second-trimester quadruple screening, with the additional advantage of an earlier diagnosis. It is comprised of ultrasound measurement of nuchal translucency thickness at 9-13 weeks gestation combined with measurement of first-trimester serum markers, β-hCG, and pregnancy-associated plasma protein A (PAPP-A). Although a positive result on a screening test (eg, low PAPP-A, elevated β-hCG) is concerning for aneuploidy (eg, trisomy 21), a definitive diagnosis can be made only by examining the fetal karyotype, which requires either chorionic villus sampling at 10-13 weeks gestation or amniocentesis after 15 weeks gestation. (Choice A) Diabetes mellitus does not affect the sensitivity or specificity of the first-trimester combined test; therefore, abnormal results require further evaluation. Although women with diabetes mellitus and elevated hemoglobin A1c values are at increased risk for congenital malformations (eg, neural tube defects), they are not at increased risk for aneuploidy. (Choice C) Repeating the first-trimester combined test does not increase sensitivity. (Choice D) This patient's first-trimester combined test results are suggestive of an increased risk of aneuploidy. However, the diagnosis of aneuploidy should be confirmed with karyotype analysis prior to pregnancy termination. Educational objective: The first-trimester combined test screens for aneuploidy by measuring nuchal translucency, β-hCG, and pregnancy-associated plasma protein A values. A positive result is confirmed by a diagnostic procedure, either chorionic villus sampling or amniocentesis, to evaluate fetal karyotype. References: Practice bulletin no.162: Prenatal diagnostic testing for genetic disorders. (http://www.ncbi.nlm.nih.gov/pubmed/26938573) Practice bulletin no. 163: Screening for fetal aneuploidy. (http://www.ncbi.nlm.nih.gov/pubmed/26938574)

A 34-Year-Old Woman, Gravida 3 Para 2, at 12 Weeks