A 36-year-old woman, gravida 1 para 0, at 10 weeks gestation comes to the office for her initial prenatal visit. The patient has had mild nausea throughout the pregnancy but can tolerate small meals. She reports no vaginal bleeding or cramping. The patient's partner has a history of male factor infertility due to low sperm count; this pregnancy is the result of an intrauterine insemination. She has no chronic medical conditions or previous surgeries. The patient has no history of abnormal Pap testing; her last Pap test was 2 years ago. She has a history of gonococcal cervicitis at age 23 but there was no evidence of tubal blockage during her infertility evaluation. The patient takes a prenatal vitamin, folic acid, and vitamin B₆ daily. She works as a high school history teacher and volleyball coach. Family history is noncontributory. The patient does not use tobacco, alcohol, or illicit drugs. Blood pressure is 98/60 mm Hg and pulse is 74/min. BMI is 23 kg/m². Cardiopulmonary examination is unremarkable. Pelvic examination reveals normal external genitalia, minimal physiologic cervical discharge throughout the vaginal vault, and a cervix with no lesions or friability. Bimanual examination reveals a retroverted uterus. Transvaginal ultrasound shows an intrauterine pregnancy with cardiac activity; crown-rump length is consistent with gestational age. In addition to routine prenatal laboratory testing, which of the following should be offered to this patient today?

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Explanation: 11ec2b69_c03d_d18d_8f63_9d979bea1724_MD0005_00 Cell-free fetal DNA testing (cffDNA) is used to screen for trisomies 13, 18, and 21 and sex chromosome aneuploidies. Noninvasive screening is routinely offered to patients at higher risk of fetal aneuploidy, including advanced maternal age (≥35) or previous pregnancy with aneuploidy. Cell-free DNA is of both maternal and fetal origin; fetal DNA is present in a large enough quantity to ensure an adequate fetal fraction for analysis at ≥10 weeks gestation. cffDNA analysis has a detection rate of 97% for trisomies 13, 18, and 21, which makes it the most sensitive screening method for these chromosomal abnormalities. The false positive rate (positive cffDNA, but unaffected fetus) is about 1%; causes include placental mosaicism, demised twin, and recent blood transfusions. Patients with a positive screening can undergo diagnostic testing (eg, chorionic villus sampling, amniocentesis) that directly analyzes the fetal genotype in chorionic villi or amniocytes. (Choice B) Hemoglobin A1c can be used to diagnose pregestational diabetes mellitus and is indicated in women with risk factors (eg, obesity, polycystic ovary syndrome). (Choice C) Universal screening for herpes simplex virus is not recommended. Serology is indicated in conjunction with a viral culture or PCR when a patient has vesicular, ulcerative lesions. (Choice D) Although school teachers are at increased risk for contracting parvovirus B19 infection, universal screening is not recommended. IgM serology is indicated only in patients with symptoms (eg, fever, rash, arthralgia) to diagnose a newly acquired infection. (Choice E) Quantitative serum β-hCG levels are indicated in pregnant patients with symptoms (eg, vaginal bleeding, pelvic pain) concerning for spontaneous abortion, hydatidiform mole, or ectopic pregnancy, particularly in early pregnancy. β-hCG levels are not indicated in patients who have an intrauterine pregnancy with cardiac activity because they do not affect management. Educational objective: Cell-free fetal DNA testing screens for trisomies 13, 18, and 21 and sex chromosome aneuploidies with high sensitivity. Due to the higher risk of chromosomal abnormalities in women of advanced maternal age (≥35), noninvasive prenatal screening with cell-free fetal DNA is routinely offered to these patients. References: Noninvasive prenatal testing. (http://www.ncbi.nlm.nih.gov/pubmed/25112487)

A 36-Year-Old Woman, Gravida 1 Para 0, at 10 Weeks