# Clinical Cases: Pregnancy Physiology

## Case 1: Gestational Trophoblastic Disease (Molar Pregnancy)

### Clinical Image
![Molar Pregnancy](case_01_image.jpg)
*Source: [Wikipedia - Hydatidiform mole](https://en.wikipedia.org/wiki/Hydatidiform_mole) - CC BY-SA 3.0*

### Case Presentation
A 38-year-old G3P2 woman at 10 weeks gestation by last menstrual period presents with vaginal bleeding and severe nausea and vomiting. She reports that her symptoms of pregnancy have been much more severe than her previous pregnancies. Physical examination reveals a uterus palpable at 16-week size (large for dates), no fetal heart tones are detected by Doppler, and blood pressure is 148/94 mmHg. Laboratory studies show beta-hCG of 285,000 mIU/mL (markedly elevated for gestational age), TSH 0.1 mIU/L (suppressed), and free T4 elevated. Transvaginal ultrasound reveals an enlarged uterus filled with heterogeneous echogenic material containing multiple anechoic spaces giving a "snowstorm" or "bunch of grapes" appearance, with no identifiable fetus or gestational sac. Bilateral ovaries contain multiple theca lutein cysts (5-6 cm each). The diagnosis is complete hydatidiform mole. After evaluation shows no evidence of metastatic disease (chest X-ray negative), suction dilation and curettage is performed. Pathology confirms complete molar pregnancy (villi with diffuse trophoblastic hyperplasia, no fetal tissue, 46,XX karyotype - all paternal). Serial beta-hCG monitoring shows appropriate decline, reaching undetectable levels by 8 weeks. She is counseled to avoid pregnancy for 6 months during surveillance.

### Key Learning Points
- Molar pregnancy results from abnormal fertilization: complete mole (46,XX, all paternal chromosomes, no fetal tissue) versus partial mole (69,XXX or XXY, triploid, some fetal tissue present)
- hCG is produced by syncytiotrophoblast; markedly elevated hCG in molar pregnancy can cause hyperthyroidism (hCG shares structural similarity with TSH) and theca lutein cysts (hCG stimulates ovarian follicles)
- Risk of progression to gestational trophoblastic neoplasia requires post-evacuation surveillance with serial beta-hCG monitoring
- Complete moles have higher malignant potential (15-20%) than partial moles (1-5%)

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## Case 2: Patent Ductus Arteriosus in Premature Infant

### Clinical Image
![Patent Ductus Arteriosus](case_02_image.jpg)
*Source: [Wikipedia - Patent ductus arteriosus](https://en.wikipedia.org/wiki/Patent_ductus_arteriosus) - CC BY-SA 3.0*

### Case Presentation
A premature male infant is born at 28 weeks gestation to a mother who presented with preterm labor. The mother received antenatal betamethasone 24 hours before delivery. The infant weighs 1100 grams and requires surfactant administration and mechanical ventilation for respiratory distress syndrome. At 5 days of life, the infant has increasing ventilator requirements and develops metabolic acidosis. Physical examination reveals a continuous "machinery" murmur best heard at the left upper sternal border, bounding peripheral pulses, and a widened pulse pressure (systolic 65, diastolic 25 mmHg). An echocardiogram confirms a moderate-sized patent ductus arteriosus with left-to-right shunting and evidence of pulmonary overcirculation with left atrial dilation. Medical management is attempted with ibuprofen (a prostaglandin synthesis inhibitor) for 3 days. Repeat echocardiogram shows significant reduction in ductal flow. The PDA closes by day 10 of life, and the infant's respiratory status improves over the following weeks.

### Key Learning Points
- In fetal circulation, the ductus arteriosus shunts blood from the pulmonary artery to the descending aorta, bypassing the non-functional lungs
- The ductus normally closes after birth due to rising oxygen tension and falling prostaglandins; prematurity is associated with delayed closure
- A patent ductus arteriosus causes left-to-right shunting after birth (now that pulmonary vascular resistance is low), leading to pulmonary overcirculation and heart failure
- Prostaglandin synthesis inhibitors (indomethacin, ibuprofen) promote ductal closure by blocking prostaglandin E2, which maintains patency

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## Case 3: Physiologic Anemia of Pregnancy

### Clinical Image
![Blood Volume in Pregnancy](case_03_image.jpg)
*Source: [Wikipedia - Pregnancy](https://en.wikipedia.org/wiki/Pregnancy) - CC BY-SA 4.0*

### Case Presentation
A 26-year-old G1P0 woman at 28 weeks gestation presents for routine prenatal care. She reports mild fatigue but is otherwise asymptomatic. She has been compliant with her prenatal vitamins. Physical examination reveals a soft systolic flow murmur (grade 2/6) and mild dependent edema, both noted at previous visits. Fundal height is appropriate for gestational age. Laboratory studies obtained as part of routine 28-week testing show hemoglobin 10.8 g/dL (down from 12.5 g/dL at her first prenatal visit), hematocrit 33%, MCV 94 fL (normal), MCH normal, and ferritin 35 ng/mL (adequate iron stores). The peripheral blood smear is unremarkable. Her complete metabolic panel and urinalysis are normal. The patient is reassured that her findings are consistent with physiologic anemia of pregnancy and do not represent true anemia requiring intervention. She is counseled about the cardiovascular adaptations of pregnancy, including the 40-50% expansion of plasma volume that exceeds the 20-30% increase in red blood cell mass, resulting in hemodilution. The mild decrease in hemoglobin is expected and actually beneficial for uteroplacental perfusion by reducing blood viscosity. No additional treatment beyond continued prenatal vitamins is recommended.

### Key Learning Points
- Pregnancy causes a 40-50% increase in plasma volume but only a 20-30% increase in RBC mass, resulting in hemodilution and lower hemoglobin concentration
- Hemoglobin levels typically reach their nadir (approximately 11-12 g/dL) around 28-32 weeks gestation
- This "physiologic anemia" is beneficial, as reduced viscosity improves uteroplacental blood flow; hemoglobin <11 g/dL in the first trimester or <10.5 g/dL in the second trimester warrants investigation for true anemia
- Other normal cardiovascular changes include increased cardiac output (30-50%), decreased systemic vascular resistance, and innocent flow murmurs