STEPTRACKERREPRODUCTIVE | PATHOLOGY + PHYSIOLOGY + PHARMACOLOGY | HIGH-YIELD REVIEW

Pregnancy Pathology

Implantation in the wrong place, placentas that sit, separate or invade wrongly, and the hypertensive disorders of pregnancy.

FOCUS ON
Ectopic: ampulla, prior PID; amenorrhea + pain + bleeding, no intrauterine sac. Third-trimester bleeding: previa = painless; abruption = painful, rigid uterus, DIC; accreta = placenta won't separate (prior C-section). Preeclampsia: abnormal spiral artery remodeling → HTN + proteinuria after 20 weeks; seizures = eclampsia (MgSO₄); HELLP.
DISORDER
MECHANISM · RISK
FEATURES
CLUE · TREATMENT
Ectopic pregnancy
Implantation outside the uterus, usually the ampulla; tubal scarring (PID/chlamydia), prior ectopic, tubal surgery, IUD in place, ART, smoking
Amenorrhea, lower abdominal pain, vaginal bleeding; hCG lower or slower than expected; empty uterus on TVUS
Rupture → hemorrhagic shock · methotrexate or surgery
Spontaneous abortion
Chromosomal abnormalities (most), antiphospholipid syndrome, uterine anomalies, teratogens, uncontrolled diabetes
Loss before 20 weeks; bleeding, cramping
Recurrent loss → APS, septate uterus, parental translocation
Placenta previa
Placenta covers or is near the internal os; prior C-section, multiparity, advanced maternal age
Painless bright red bleeding in the third trimester
Ultrasound first — no digital exam
Placental abruption
Premature separation from the decidua; hypertension, cocaine, smoking, trauma
Painful bleeding, tender rigid uterus, fetal distress; bleeding may be concealed
DIC, hypovolemic shock · Couvelaire uterus
Placenta accreta spectrum
Defective decidua basalis (prior C-section scar, previa) → villi attach to (accreta), into (increta) or through (percreta) the myometrium
Placenta fails to separate → massive postpartum hemorrhage; percreta may invade bladder
Planned cesarean hysterectomy
Vasa previa
Fetal vessels cross the membranes over the internal os
Painless bleeding at rupture of membranes + fetal bradycardia
Fetal blood loss — emergency C-section
Preeclampsia
Shallow trophoblast invasion → spiral arteries not remodeled → placental ischemia → sFlt-1, soluble endoglin → maternal endothelial dysfunction
BP ≥ 140/90 after 20 weeks + proteinuria or end-organ damage (headache, visual change, RUQ pain, ↓ platelets, ↑ creatinine)
Delivery cures · labetalol, hydralazine, nifedipine · aspirin prevents in high risk
Eclampsia
Preeclampsia + cerebral endothelial injury
New-onset seizures
MgSO₄ · toxicity: ↓ reflexes, respiratory depression → calcium gluconate
HELLP syndrome
Severe endothelial injury with microangiopathy
Hemolysis (schistocytes), Elevated Liver enzymes, Low Platelets; RUQ pain
Hepatic hematoma/rupture, DIC · deliver
Acute fatty liver of pregnancy
Fetal LCHAD deficiency → fatty acids overload maternal liver → microvesicular steatosis
Third trimester: nausea, jaundice, hypoglycemia, liver failure, DIC
Deliver promptly
Gestational diabetes
Placental hPL and other hormones → insulin resistance
Macrosomia, shoulder dystocia, neonatal hypoglycemia; screen at 24–28 weeks
Diet → insulin or metformin
Amniotic fluid embolism
Fetal material enters maternal circulation → anaphylactoid reaction
Sudden dyspnea, hypoxia, hypotension, DIC during labor or just after
Fetal squames in pulmonary vessels

Mechanism — preeclampsia

Shallow trophoblast invasion
→
Narrow spiral arteriesPlacental hypoxia
→
sFlt-1 + soluble endoglinBind VEGF, PlGF, TGF-β
→
Endothelial dysfunctionVasoconstriction, leak
→
HTN, proteinuria, seizures, HELLP

Kidney lesion: glomerular endotheliosis (swollen endothelial cells). Preeclampsia before 20 weeks → molar pregnancy.

Amniotic fluid abnormalities

POLYHYDRAMNIOS (can't swallow / ↑ urine)
OLIGOHYDRAMNIOS (no urine / leak)
Esophageal or duodenal atresia
Bilateral renal agenesis, ARPKD
Anencephaly (no swallowing)
Posterior urethral valves
Maternal diabetes (fetal polyuria)
Placental insufficiency
Fetal anemia, multiple gestation
Rupture of membranes; ACE inhibitors

How it's tested

COMMON CONFUSIONPrevia bleeds painlessly; abruption hurts and the uterus is hard. Vasa previa bleeds at membrane rupture and the fetal heart rate drops.
THE TRAPNever do a digital cervical exam with third-trimester bleeding until previa is ruled out by ultrasound.
YOUR APPROACHTrimester → pain or not → hCG/US (ectopic) → BP and labs (preeclampsia, HELLP, AFLP) → treatment (methotrexate, MgSO₄, delivery).

If you see… think…

Missed period, pelvic pain, spotting, empty uterus on TVUS → ectopic pregnancy
Most common site of ectopic → ampulla of fallopian tube
Painless bright red bleeding at 32 weeks → placenta previa
Cocaine use, painful bleeding, rigid uterus, DIC → placental abruption
Two prior C-sections + previa, placenta won't separate → placenta accreta
Bleeding at membrane rupture + fetal bradycardia → vasa previa
BP 160/110, proteinuria, headache at 34 weeks → preeclampsia with severe features
Preeclampsia + seizure → eclampsia — magnesium sulfate
Lost reflexes and slow breathing on MgSO₄ → Mg toxicity — calcium gluconate
Third trimester jaundice + hypoglycemia + microvesicular fat → acute fatty liver of pregnancy