Human Chorionic Gonadotropin (hCG) Measured in urine or blood blood test more sensitive Produced by syncytiotrophoblast of the placenta after implantation Used to detect pregnancy can see pregnancy on transvaginal ultrasound after hCG reaches 1,500-2,000 mIU/mL Urine Estriol Measured in maternal urine Produced by fetal adrenal gland maternal liver placenta Sign of fetal growth ↓ estriol is sign of fetal-maternal-placental dysfunction α-Fetoprotein (AFP) Measured in maternal serum ↑ AFP associated with open neural tube defects ↓ AFP associated with Down syndrome Lecithin/Sphingomyelin (L:S) Ratio Measured in amniotic fluid lecithin is a surfactant produced by fetal lungs used to determine maturity of fetal lungs L:S ratio > 2 indicates maturity L:S ratio < 2 administration of cortisol ↑ lecithin production fetus normally produces during the stress of vaginal delivery thyroxine also ↑ lethicin production insulin ↓ production First Trimester Screen (10-13 weeks) Serum labs serum free β-hCG or total hCG ↑ trisomy 21 ↓ trisomy 18 ↓ trisomy 13 pregnancy-associated plasma protein A (PAPP-A) ↓ trisomy 21 ↓ trisomy 18 ↓ trisomy 13 Imaging nuchal translucency measurement ↑ trisomy 21 ↑ trisomy 18 Quadruple Screen (15-22 weeks) Test for aneuploidy hCG ↑ trisomy 21 ↓ trisomy 18 alpha fetoprotein (AFP) ↓ trisomy 21 ↓ trisomy 18 dimeric inhibin A ↑ trisomy 21 no change or ↓ trisomy 18 unconjugated estriol ↓ trisomy 21 ↓ trisomy 18