A 61-year-old woman presents for a routine health visit. She complains of generalized fatigue and lethargy on most days of the week for the past 4 months. She has no significant past medical history and is not taking any medications. She denies any history of smoking or recreational drug use but states that she drinks "socially" approx. 6 nights a week. She says she also enjoys a "nightcap," which is 1–2 glasses of wine before bed every night. The patient is afebrile, and her vital signs are within normal limits. On physical examination, there is significant pallor of the mucous membranes. Laboratory findings are significant for a mean corpuscular volume (MCV) of 72 fL, leukocyte count of 4,800/mL, hemoglobin of 11.0 g/dL, and platelet count of 611,000/mL. Stool guaiac test is negative. She is started on oral ferrous sulfate supplements. On follow-up, her laboratory parameters show no interval change in her MCV or platelet level, and she reports good compliance with the medication. Which of the following is the best next step in the management of this patient?

Transfuse the patient with whole blood

Continue oral ferrous sulfate and supplement with omeprazole

Continue oral ferrous sulfate and supplement with ascorbic acid

A 36-year-old primigravid woman who recently immigrated to the United States presents to her gynecologist for the first time during the 28th week of her pregnancy. She hasn’t received any prenatal care or folic acid supplementation. The patient’s history reveals that she has received blood transfusions in the past due to “severe anemia.” Which of the following blood type situations would put the fetus at risk for hemolytic disease of the newborn?

Mother is A negative, father is B positive

Mother is AB negative, father is O negative

Mother is O positive, father is B negative

Mother is O positive, father is AB negative

Mother is B positive, father is O negative

A 27-year-old African-American woman, gravida 1, para 0, at 11 weeks' gestation comes to her physician for a prenatal visit. She feels more fatigued than usual but has no other symptoms. She has no history of serious illness. She takes no medications. Her mother has systemic lupus erythematosus. Her temperature is 37.2°C (98.9°F), pulse is 80/min, respirations are 18/min, and blood pressure is 120/75 mm Hg. Examination shows no abnormalities. Laboratory studies show: Hemoglobin 9.2 g/dL Hematocrit 27.5% Leukocyte count 6,000/mm3 Platelet Count 180,000/mm3 MCV 74 μm3 MCH 24 pg/cell Serum Na+ 138 mEq/L K+ 4.5 mEq/L Cl- 100 mEq/L HCO3- 25 mEq/L Urea Nitrogen 15 mg/dL Creatinine 1.0 mg/dL Total Bilirubin 0.4 mg/dL Iron 67 U/L Ferritin 98 ng/mL Which of the following is the most appropriate next step in management?

Measure anticardiolipin antibody titers

A 27-year-old woman, gravida 2, para 1, at 36 weeks' gestation comes to the physician for a prenatal visit. She feels well. Fetal movements are adequate. This is her 7th prenatal visit. She had an ultrasound scan performed 1 month ago that showed a live intrauterine pregnancy consistent with a 32-week gestation with no anomalies. She had a Pap smear performed 1 year ago, which was normal. Vital signs are within normal limits. Pelvic examination shows a uterus consistent in size with a 36-week gestation. Her blood group and type is A negative. Which of the following is the most appropriate next step in management?

Transabdominal doppler ultrasonography

A 29-year-old G1P0 presents to her obstetrician for her first prenatal care visit at 12 weeks gestation by last menstrual period. She states that her breasts are very tender and swollen, and her exercise endurance has declined. She otherwise feels well. She is concerned about preterm birth, as she heard that certain cervical procedures increase the risk. The patient has a gynecologic history of loop electrosurgical excision procedure (LEEP) for cervical dysplasia several years ago and has had negative Pap smears since then. She also has mild intermittent asthma that is well controlled with occasional use of her albuterol inhaler. At this visit, this patient’s temperature is 98.6°F (37.0°C), pulse is 69/min, blood pressure is 119/61 mmHg, and respirations are 13/min. Cardiopulmonary exam is unremarkable, and the uterine fundus is just palpable at the pelvic brim. Pelvic exam reveals normal female external genitalia, a closed and slightly soft cervix, a 12-week-size uterus, and no adnexal masses. Which of the following is the best method for evaluating for possible cervical incompetence in this patient?

Transvaginal ultrasound at 18 weeks gestation

Transabdominal ultrasound in the first trimester

Transvaginal ultrasound in the first trimester

Serial transvaginal ultrasounds starting at 16 weeks gestation

Transabdominal ultrasound at 18 weeks gestation

A 26-year-old woman presents to the women’s health clinic with a 9-week delay in menses. The patient has a history of grand mal seizures, and was recently diagnosed with acute sinusitis. She is prescribed lamotrigine and amoxicillin. The patient smokes one-half pack of cigarettes every day for 10 years, and drinks socially a few weekends every month. Her mother died of breast cancer when she was 61 years old. The vital signs are stable during the current office visit. Physical examination is grossly normal. The physician orders a urine beta-hCG that comes back positive. Abdominal ultrasound shows an embryo consistent in dates with the first day of last menstrual period. Given the history of the patient, which of the following would most likely decrease congenital malformations in the newborn?

Switching to another antiepileptic medication

Anemia in pregnancy for USMLE Step 2 CK: High-Yield OB/GYN Lessons

Physiology & Definition - The Dilution Effect

Pregnancy causes a greater expansion of plasma volume (↑ ~50%) compared to red blood cell (RBC) mass (↑ ~25-30%).
This disproportionate increase results in hemodilution, a physiologic decrease in hemoglobin (Hb) and hematocrit (Hct).
Anemia Thresholds (CDC):
- 1st Trimester: Hb < 11 g/dL
- 2nd Trimester: Hb < 10.5 g/dL
- 3rd Trimester: Hb < 11 g/dL

⭐ The nadir of physiologic anemia occurs in the late second trimester, coinciding with peak plasma volume.

Physiologic Changes in Pregnancy

Etiology & Diagnosis - Finding the Cause

Initial Workup: Start with a Complete Blood Count (CBC).
- Anemia: Hemoglobin <11 g/dL (1st/3rd trimester) or <10.5 g/dL (2nd trimester).
Classification by MCV:
- Microcytic (MCV <80 fL): Most common type.
  - Iron Deficiency Anemia (IDA): Check iron studies (↓ Ferritin, ↑ TIBC).
  - Thalassemia: Hemoglobin electrophoresis.
- Normocytic (MCV 80-100 fL):
  - Physiologic hemodilution, anemia of chronic disease.
- Macrocytic (MCV >100 fL):
  - Folate or Vitamin B12 deficiency.

⭐ Serum ferritin is the most sensitive and specific test for iron deficiency in pregnancy; a level <30 ng/mL is diagnostic.

Peripheral blood smear: microcytic hypochromic anemia

Screening & Workup - The Rightful Algorithm

Universal Screening: CBC at the initial prenatal visit & repeated at 24-28 weeks.
Anemia Thresholds:
- 1st & 3rd Trimesters: Hb < 11 g/dL
- 2nd Trimester: Hb < 10.5 g/dL

Peripheral blood smear: microcytic, hypochromic RBCs

⭐ High-Yield: Serum ferritin is the most sensitive and specific test for iron deficiency. A level < 30 ng/mL confirms iron deficiency anemia in pregnancy.

Management - Boosting the Blood

Iron Deficiency Anemia (IDA):
- First-line: Oral ferrous sulfate (325 mg daily).
- Take with Vitamin C to ↑ absorption.
- IV iron for malabsorption, PO intolerance, or severe anemia near term.
Folate/B12 Deficiency: Replete the deficient vitamin.
Packed RBC Transfusion: For Hgb < 7 g/dL, hemodynamic instability, or acute hemorrhage.

⭐ Fetal iron uptake is preserved even in severe maternal deficiency; the fetus effectively acts as an iron parasite.

Complications - Risks for Two

Maternal Risks:
- Impaired cardiac function → high-output failure (if Hb < 6 g/dL)
- Preeclampsia
- ↑ Postpartum hemorrhage (PPH) & infection risk
- Poor tolerance to blood loss at delivery
Fetal & Neonatal Risks:
- Low birth weight (LBW) & IUGR
- Preterm delivery
- Intrauterine fetal demise (IUFD)
- Lower iron stores → neonatal anemia

⭐ Maternal iron deficiency anemia, especially in the first two trimesters, is associated with an increased risk of autism spectrum disorder, ADHD, and intellectual disability in the child.

Fetus, red blood cells, and iron supplements

High‑Yield Points - ⚡ Biggest Takeaways

Physiologic anemia of pregnancy is the most common type, resulting from hemodilution (plasma volume ↑ > RBC mass ↑).

Iron deficiency is the most common pathologic cause; screen with a CBC at the first prenatal visit and again at 24-28 weeks.

Diagnostic thresholds: Hb <11 g/dL in the 1st/3rd trimesters, and <10.5 g/dL in the 2nd.

Low serum ferritin is the most sensitive and specific test for iron deficiency.

Treat with oral ferrous sulfate; parenteral iron is reserved for severe cases or malabsorption.

Folate deficiency causes megaloblastic anemia and increases the risk of neural tube defects.

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