A 36-year-old woman, gravida 1 para 0, at 26 weeks gestation comes to the office for routine prenatal care. The patient reports good fetal movement and has no concerns. She initiated prenatal care at 12 weeks gestation and an ultrasound at that time was consistent with her last menstrual period. She declined all genetic testing. Anatomy ultrasound performed at 19 weeks revealed an estimated fetal weight consistent with 18 weeks gestation and an atrial septal defect. The patient has a history of depression for which she takes citalopram. She quit smoking cigarettes prior to conception and does not use alcohol or illicit drugs. Prepregnancy BMI was 23 kg/m² and her weight gain has been appropriate. Blood pressure is 138/89 mm Hg. Fundal height is 22 cm and fetal heart tones are heard by Doppler. An ultrasound reveals fetal head circumference, abdominal circumference, and estimated fetal weight at the 4th percentile. Normal amniotic fluid level and a fundal placenta are present. A biophysical profile is 8/8. Umbilical artery Dopplers are normal. Which of the following is the most likely cause of these fetal findings?

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11ec25c8_da2c_ab7e_bc81_ad71f403d9b6_MD0003_00 Fetal growth restriction (FGR) is an ultrasound-estimated fetal weight <10th percentile for gestational age. FGR can be symmetric or asymmetric. Symmetric FGR is a global, proportionate growth lag that affects fetal organs uniformly and begins during the first trimester. Causes of symmetric FGR include fetal chromosomal anomalies and first trimester/congenital infection (eg, toxoplasmosis, cytomegalovirus). In asymmetric FGR, abdominal growth restriction is more pronounced than growth restriction of the head as a result of fetal adaptation to chronic placental insufficiency. Maternal vasculopathy (eg, hypertension, pregestational diabetes) can cause inadequate utero-placental perfusion and chronic fetal hypoxia. In response, fetal redistribution of blood flow to vital organs (eg, brain, heart, placenta) occurs at the expense of less vital organs (eg, abdominal viscera), resulting in "head-sparing" FGR. This fetus has an estimated weight <10th percentile and a symmetric growth lag of the head and abdomen. The growth lag seen at the anatomy ultrasound suggests a process that started early in pregnancy. The atrial septal defect and this patient's age (>35) are suggestive of an underlying chromosomal abnormality (eg, trisomy 21). (Choice B) Intrauterine infection (eg, toxoplasmosis, cytomegalovirus) is an uncommon cause of symmetric FGR. Ultrasound typically reveals multiple abnormalities, including intracerebral calcifications and ventriculomegaly. In addition, intrauterine infection typically follows maternal illness, which was not seen in this patient. (Choice C) Inaccurate pregnancy dating can result in an erroneous diagnosis of FGR. This patient has accurate dating from a first-trimester ultrasound that is consistent with her last menstrual period. (Choices D and F) Maternal hypertension and tobacco use during pregnancy are associated with asymmetric FGR. (Choice E) Maternal depression is associated with an increased risk for cognitive delay and psychiatric illness (eg, depression, attention-deficit disorder) but is not associated with FGR. Citalopram, a selective serotonin reuptake inhibitor, is neither teratogenic nor associated with FGR. Educational objective: Symmetric fetal growth restriction (FGR) begins in the first trimester and is due to fetal conditions such as aneuploidy, congenital anomalies, and intrauterine infection. Asymmetric FGR occurs in the second and third trimesters and is due to maternal conditions that cause placental insufficiency (eg, hypertension). References: ACOG practice bulletin no. 134: fetal growth restriction. (http://www.ncbi.nlm.nih.gov/pubmed/23635765) Fetal growth restriction: current knowledge to the general obs/gyn. (http://www.ncbi.nlm.nih.gov/pubmed/22526452)

A 36-Year-Old Woman, Gravida 1 Para 0, at 26 Weeks