A boy is brought to the nursery shortly after birth. The patient was born at term to a 36-year-old primigravid mother via spontaneous vaginal delivery following a pregnancy complicated by chronic hypertension. Her only prenatal care was at 10 weeks gestation in the emergency department and was due to vaginal discharge and spotting. Ultrasound confirmed a 10-week intrauterine gestation. The mother was diagnosed with Chlamydia trachomatis and treated with azithromycin. The infant was born vigorous with Apgar scores of 7 and 9 at 1 and 5 minutes, respectively. The patient's measurements are charted below, and the examination is otherwise unremarkable. Which of the following is the most likely cause of this patient's findings?

Question

A boy is brought to the nursery shortly after birth.  The patient was born at term to a 36-year-old primigravid mother via spontaneous vaginal delivery following a pregnancy complicated by chronic hypertension.  Her only prenatal care was at 10 weeks gestation in the emergency department and was due to vaginal discharge and spotting.  Ultrasound confirmed a 10-week intrauterine gestation.  The mother was diagnosed with Chlamydia trachomatis and treated with azithromycin.  The infant was born vigorous with Apgar scores of 7 and 9 at 1 and 5 minutes, respectively.  The patient's measurements are charted below, and the examination is otherwise unremarkable.  Which of the following is the most likely cause of this patient's findings?

Quizplus · Accepted Answer

Explanation: 11ec25c8_d70c_0a09_bc81_d3a8fa324ba3_MD0003_00 Fetal growth restriction (FGR) is characterized by an estimated fetal weight <10th percentile or birth weight <3rd percentile for gestational age. Neonates who are small for gestational age (SGA) (ie, birth weight <10th percentile) are also considered growth restricted if maternal risk factors for poor fetal growth are present (eg, maternal hypertension, preeclampsia). FGR is characterized as: Symmetric, in which all growth parameters are small Asymmetric, in which weight is low but head circumference is normal ("head-sparing"), as seen in this patient. Whereas symmetric FGR is typically due to an insult early in pregnancy (eg, genetic condition, congenital infection), asymmetric FGR is most commonly caused by decreased blood flow and oxygen delivery to the fetus (ie, uteroplacental insufficiency) in the second/third trimester. Asymmetric FGR is "head-sparing" because nutrient delivery is preferentially redistributed to essential organs (eg, brain, heart). The most likely cause of uteroplacental insufficiency in this case is maternal chronic hypertension. Management of newborns with FGR includes prevention and treatment of associated complications such as hypoglycemia, polycythemia, hypothermia, and poor feeding. Catch-up growth is typically achieved by age 2, but long-term growth and neurodevelopment abnormalities can occur. (Choices A and D) Congenital infection (eg, cytomegalovirus) and teratogenic drug exposure (eg, warfarin) can cause symmetric FGR, which is not present in this patient with a normal head circumference. Untreated maternal chlamydial infection can be transmitted during delivery and cause neonatal conjunctivitis and pneumonia but does not affect fetal growth. In addition, azithromycin is not teratogenic. (Choice B) Inaccurate pregnancy dating can make all growth parameters appear falsely low relative to presumed gestational age. However, a first-trimester ultrasound is highly accurate in establishing dating. (Choice C) Constitutional SGA is a variant of normal growth in which a neonate is small in length and weight due to genetics (ie, small parents). In contrast, this patient has asymmetric growth parameters and risk factors for placental insufficiency (maternal chronic hypertension), making pathologic FGR more likely. Educational objective: Fetal growth restriction (FGR) is characterized by estimated fetal weight <10th percentile or birth weight <3rd percentile. Asymmetric FGR, in which head circumference is normal, is most commonly due to uteroplacental insufficiency (eg, maternal chronic hypertension) in the second/third trimester. References: Intrauterine growth restriction: antenatal and postnatal aspects. (http://www.ncbi.nlm.nih.gov/pubmed/27441006)

A Boy Is Brought to the Nursery Shortly After Birth