Antenatal Visits and Investigations

A 28-year-old primigravida at 16 weeks of gestation attends her first antenatal visit. She is asymptomatic with a normal obstetric examination. Her booking blood tests show: Hb 11.2 g/dL, blood group O positive, negative infectious serology (HIV, HBsAg, VDRL, rubella IgM). She has no significant past medical history. What is the most appropriate next investigation at this visit?

A 28-year-old primigravida at 16 weeks gestation presents for routine antenatal care. Serum alpha-fetoprotein (AFP) is elevated at 2.5 MoM (multiples of median). She is anxious about fetal anomalies. What is the most appropriate next investigation?

A 28-year-old primigravida at 32 weeks of gestation is screened for anemia. Her hemoglobin is 9.5 g/dL. Which laboratory finding best distinguishes iron deficiency anemia from anemia of chronic disease in pregnancy?

A 32-year-old multigravida at 20 weeks of gestation presents for her routine antenatal visit. She reports no complaints. Obstetric examination is unremarkable. Her first-trimester combined screening (NT + biochemistry) showed a low risk for chromosomal abnormalities (risk 1 in 2500). She has no significant past medical history and is not diabetic. What is the most appropriate next investigation at this visit?

During routine antenatal care at 16 weeks of gestation, a 32-year-old woman undergoes the triple screen (maternal serum screening). Which is the most common chromosomal abnormality detected by this test in the Indian population?