Snapshot A 35-year-old G3P0 woman at 30 weeks gestation presents to her obstetrician for a routine prenatal visit. She has had an unremarkable pregnancy with normal fetal ultrasounds. She has no medical conditions, but has been smoking throughout pregnancy. She denies the use of alcohol or drugs. Physical exam is significant for a fundal height of 25 cm and a normal fetal heart rate tracing. Ultrasound reveals a fetus with a head circumference consistent with 33 weeks gestation and an abdominal circumference consistent with 23 weeks gestation. Estimated fetal weight is at the 6th percentile for gestational age. Introduction Clinical definition Estimated fetal weight below the 10th percentile for a given gestational age Classified as symmetric intrauterine growth restriction (IUGR) proportional reduction in head, body, and length asymmetric IUGR preservation of head circumference and reduction in trunk and limb length Epidemiology Epidemiology of Symmetric vs Asymmetric IUGR Symmetric Asymmetric Risk factors Intrinsic factors genetic abnormalities congenital infections congenital heart disease Extrinsic factors chronic maternal disease (e.g., hypertension, renal failure, diabetes) pre-eclampsia smoking drug use alcohol use teratogenic drugs (e.g., ACE inhibitors, phenytoin, warfarin) Pathophysiology Caused by a global perturbation of fetal growth due to intrinsic fetal problems trisomy 18 renal agenesis infections ToRCHeS rubella infection toxoplasmosis caused by placental insufficiency secondary to intrinsic placental defects or decreased maternal blood flow to the placenta the fetus now selectively shunts blood flow to the most critical and needed areas (e.g., brain) and away from limbs and abdomen Prognosis increased neonatal mortality increased risk of pre-term birth increased risk of disease in adulthood type II diabetes mellitus obesity cardiovascular disease renal disease Worse prognosis with early onset and increasing severity of growth restriction Presentation Physical exam neonatal findings inspection thin, loose, and peeling skin decreased muscle mass decreased subcutaneous fat thin umbilical cord shrunken face larger than expected anterior fontanelle meconium-stained infant motion decreased or absent fetal movement maternal findings inspection fundal height discrepancy Imaging Ultrasonography indications to confirm the diagnosis in patients with a history and physical exam findings concerning for IUGR findings decreased fetal weight below 10th percentile of a given gestational age fetal biphysical profile amniotic fluid volume fetal movement and tone fetal breathing movement heart rate reactivity doppler velocimetry reduced or absent doppler flow measurements of head and abdominal circumference, biparietal diameter, and femur length Studies Labs screening for congenital infections genetic amniocentesis ultrasonography to detect fetal anomalies Differential Small for gestational age key distinguishing factor estimated weight less than the 10th percentile for a given gestational age Incorrect pregnancy dating key distinguishing factor ultrasound measurements for dating Oligohydramnios key distinguishing factor ultrasound findings demonstrating estimated weight less than the 10th percentile for a given gestational age Treatment Conservative close fetal monitoring indication in cases of asymmetric IUGR in order to identify fetuses at risk of intrauterine demise and neonatal morbidity in order to determine if pre-term delivery is needed modalities serial ultrasounds umbilical artery Doppler nonstress test and biophysical profile delivery indications in cases of severe IUGR with signs of non-reassuring fetal status if the fetus is close to term, administer steroids and deliver within 48 hours modalities cessarean delivery vaginal delivery Complications Maternal pre-eclampsia Perinatal death Premature delivery Hypoglycemia Polycythemia Impaired cellular immunity Hypocalcemia