A 42-year-old woman comes to the office after a positive home pregnancy test. The patient has a history of irregular menses and had a positive home pregnancy test after she went 6 months without a menstrual period. Her medical conditions include chronic hypertension, for which she takes multiple medications, and type 2 diabetes mellitus, for which she stopped taking metformin a few months ago due to side effects. BMI is 38 kg/m². Temperature is 37.6 C (100 F), blood pressure is 138/88 mm Hg, and pulse is 90/min. The abdomen is soft and without rebound or guarding. The uterus is nontender and fundal height measures 24 cm. Ultrasound findings show a singleton fetus at 24 weeks gestation with bilateral small, underdeveloped kidneys and a bladder with minimal urine. The amniotic fluid index is 4 cm (normal: 5 cm). Which of the following is the most likely cause of this fetal presentation?

Question

A 42-year-old woman comes to the office after a positive home pregnancy test. The patient has a history of irregular menses and had a positive home pregnancy test after she went 6 months without a menstrual period. Her medical conditions include chronic hypertension, for which she takes multiple medications, and type 2 diabetes mellitus, for which she stopped taking metformin a few months ago due to side effects. BMI is 38 kg/m². Temperature is 37.6 C (100 F), blood pressure is 138/88 mm Hg, and pulse is 90/min. The abdomen is soft and without rebound or guarding. The uterus is nontender and fundal height measures 24 cm. Ultrasound findings show a singleton fetus at 24 weeks gestation with bilateral small, underdeveloped kidneys and a bladder with minimal urine. The amniotic fluid index is 4 cm (normal: >5 cm). Which of the following is the most likely cause of this fetal presentation?

Quizplus · Accepted Answer

11ec25c8_da8a_0d6d_bc81_bffc8c7feb93_MD0003_00 This patient's prenatal ultrasound shows bilateral small, underdeveloped fetal kidneys consistent with fetal renal hypoplasia. These fetal findings, in addition to the patient's history of chronic hypertension managed with multiple medications, are likely due to maternal use of an ACE inhibitor or angiotensin II receptor blocker (ARB), which are teratogens. During pregnancy, angiotensin II is required for both fetal renal development and maintenance of fetal glomerular filtration rate. Both ACE inhibitors (which prevent the conversion of angiotensin I to II) and ARBs (which block angiotensin II at the angiotensin II receptor type 1) decrease angiotensin II activity, resulting in defects in fetal renal development (eg, renal hypoplasia, dysgenesis). Hypoplastic kidneys are unable to produce urine; therefore, fetal ultrasound typically reveals a small fetal bladder with minimal urine. The lack of urine production is exacerbated by a decreased fetal glomerular filtration rate, causing oligohydramnios (ie, amniotic fluid index ≤5 cm). Because amniotic fluid is required for fetal lung development and protection against limb compression, fetuses with severe oligohydramnios are also at risk for pulmonary hypoplasia and facial or limb defects (ie, Potter sequence). Potter sequence Because of these risks, women of childbearing age should not be started on ACE inhibitors or ARBs if other options are available. Those taking an ACE inhibitor or ARB should stop these medications prior to pregnancy. (Choice A) Autosomal recessive polycystic kidney disease can present with oligohydramnios; however, fetal ultrasound typically reveals bilaterally enlarged, cystic kidneys rather than renal hypoplasia. (Choice B) Chromosomal aneuploidy (eg, trisomy 18) is more common in women of advanced maternal age and can cause renal defects (eg, horseshoe kidney); however, fetuses typically have anomalies affecting multiple organ systems (eg, cardiac defects, omphalocele) rather than isolated renal hypoplasia. (Choice D) Posterior urethral valves, membranes obstructing the urethra, can cause oligohydramnios due to decreased fetal urine output. However, the backup of urine typically causes a distended fetal bladder and bilateral hydronephrosis. Posterior urethral valves (Choice E) Uncontrolled pregestational diabetes mellitus typically causes cardiac (eg, septal defects, tetralogy of Fallot) and nervous system (eg, neural tube defects, sacral agenesis) defects that correlate with the severity of maternal hyperglycemia. Isolated fetal renal hypoplasia is uncommon. (Choice F) Vesicoureteral reflux, the retrograde travel of urine from the bladder to the ureter, typically causes enlarged fetal kidneys due to hydronephrosis. Educational objective: ACE inhibitors and angiotensin II receptor blockers are teratogens. The use of either medication during pregnancy can cause fetal renal hypoplasia (eg, bilateral, underdeveloped fetal kidneys) and oligohydramnios. References: Renin-angiotensin system blocker fetopathy. (http://www.ncbi.nlm.nih.gov/pubmed/26254838) The management of hypertension in women planning for pregnancy. (http://www.ncbi.nlm.nih.gov/pubmed/30371746)

A 42-Year-Old Woman Comes to the Office After a Positive