A 28-year-old woman, gravida 1 para 0, at 30 weeks gestation comes to the
labor and delivery unit due to painful contractions for the past several hours. She did not receive any
prenatal care. Temperature is 37.0°C (98.6°F),
pulse is 94/min, and
blood pressure is 135/84 mmHg. The fetal ultrasound shows an amniotic fluid index of 24 cm (normal 8-18) with the single deepest pocket measuring 9 cm. She denies any gush of fluid. Pelvic examination reveals a
uterus size consistent with 34 weeks of gestation. Which of the following is the most likely cause of this patient presentation?
