What is the diagnosis for a 39-year-old woman, gravida (number of times pregnant) 2, para (number of viable births) 1, at 28 weeks gestation, presenting with painful uterine contractions, rupture of membranes (ROM), and an anencephalic (absence of a major portion of the brain) fetus in breech presentation?

Differential Diagnosis

• Single most likely diagnosis
  • Preterm labor with premature rupture of membranes (PROM): The patient is experiencing painful uterine contractions, has a dilated and effaced cervix, and has passed clear fluid from her vagina, which is nitrazine-positive, indicating the presence of amniotic fluid. The ultrasound also shows anhydramnios, which is consistent with ruptured membranes.
• Other Likely diagnoses
  • Incompetent cervix: The patient's cervix is 4 cm dilated and 80% effaced at 28 weeks gestation, which could indicate cervical incompetence, especially given the lack of significant uterine contractions or other risk factors for preterm labor.
  • Intrauterine infection: Although the patient's temperature is normal, intrauterine infection is a possible cause of preterm labor and PROM, and should be considered, especially if the patient's condition worsens or if there are other signs of infection.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Placental abruption: Although the patient's ultrasound shows an anencephalic fetus and anhydramnios, placental abruption is a life-threatening condition that can cause preterm labor and vaginal bleeding, and should be considered, especially if the patient's condition worsens or if there are other signs of abruption.
  • Uterine rupture: Although rare, uterine rupture is a life-threatening condition that can cause severe abdominal pain, vaginal bleeding, and fetal distress, and should be considered, especially if the patient has a history of uterine surgery or if there are other risk factors.
• Rare diagnoses
  • Amniotic fluid embolism: Although rare, amniotic fluid embolism is a life-threatening condition that can cause sudden onset of symptoms, including respiratory distress, hypotension, and fetal distress, and should be considered if the patient's condition suddenly worsens.
  • Chorioamnionitis: Although rare, chorioamnionitis is a serious infection of the placenta and amniotic fluid that can cause preterm labor, PROM, and fetal distress, and should be considered if the patient's condition worsens or if there are other signs of infection.