Review Question - QID 212815

A 25-year-old G1P0 at 20 weeks of gestation woman arrives at a prenatal appointment complaining of pelvic pressure. She has had an uncomplicated pregnancy thus far. She takes prenatal vitamins and eats a well-balanced diet. Her medical history is significant for major depressive disorder that has been well-controlled on citalopram. Her mother had gestational diabetes with each of her 3 pregnancies. On physical exam, the cervix is soft and closed with minimal effacement. There is white vaginal discharge within the vagina and vaginal vault without malodor. Vaginal pH is 4.3. A transvaginal ultrasound measures the length of the cervix as 20 mm. Which of the following is most likely to prevent preterm birth in this patient?