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?