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

Picture it — where the pregnancy or placenta sits

NormalPlacenta at the fundus, clear of the cervical os.

Placenta previaPlacenta over the os → painless bleeding.

AbruptionClot behind the placenta → painful bleeding, tender uterus.

Accreta spectrumVilli grow into the myometrium (no decidua).

Vasa previaFetal vessels cross the os → fetal blood loss at rupture.

EctopicMost often in the ampulla of the fallopian tube.

Schematic diagrams, not to scale. Red = abnormal.

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