A 32-year-old primigravid woman at 21 weeks gestation comes to the office due to increased vaginal discharge. The discharge started a week ago and initially was clear but turned slightly bloody today. The patient has had no abdominal pain or heavy vaginal bleeding. The patient has no chronic medical conditions and has had no prior surgeries. Temperature is 36.8 C (98.2 F), blood pressure is 96/62 mm Hg, and pulse is 92/min. BMI is 19 kg/m². The uterus is nontender, fundal height is 19 cm, and fetal heart tones are 155/min. Speculum examination shows scant blood and discharge; a bulging bag with fetal parts is protruding through the cervix, which is dilated 4 cm. Microscopy of the vaginal discharge shows squamous epithelial cells and few leukocytes. Nitrazine testing is negative. Which of the following is the most likely diagnosis in this patient?

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11ec25c8_da41_4419_bc81_592b740076ad_MD0003_00 This patient has cervical insufficiency, a structural weakness of the cervix causing spontaneous, painless cervical dilation and potential second-trimester pregnancy loss. Risk factors include collagen abnormalities (eg, Ehlers-Danlos syndrome), uterine anomalies (eg, septate or bicornuate uterus), prior obstetric trauma, and cervical conization. Patients with cervical insufficiency, even those presenting with advanced cervical dilation, typically have only mild symptoms such as increased vaginal discharge (due to loss of the mucus plug), light vaginal bleeding (due to cervical stretching), and pelvic pressure (due to fetal parts distending the upper vagina). cervical conization Patients can be diagnosed on examination, which reveals visible cervical dilation and no uterine contractions. These patients are typically managed with a rescue cerclage, in which a suture is placed to reinforce and add tensile strength to the cervix to prevent further dilation. However, in patients who have bulging or prolapsing amniotic membranes, a rescue cerclage is not typically recommended due to the high risk of membrane rupture, complications (eg, intraamniotic infection, cervical trauma), and likely imminent delivery. suture (Choice A) Abruptio placentae may cause bloody vaginal discharge, but it typically presents with painful contractions and uterine tenderness, which are not seen in this patient. Abruptio placentae (Choice C) An incomplete abortion can present with cervical dilation and fetal parts at the cervical os; however, it is defined as pregnancy loss at <20 weeks gestation, whereas this patient is at 21 weeks. In addition, it is typically painful due to uterine cramping. In future pregnancies, management of patients with a prior spontaneous abortion is typically expectant; in contrast, those who meet criteria for cervical insufficiency may benefit from a prophylactic cerclage. incomplete abortion (Choice D) In contrast to this patient's painless presentation, patients in preterm labor typically have regular, painful uterine contractions leading to cervical dilation. (Choice E) Preterm prelabor rupture of membranes can cause increased clear or slightly bloody vaginal discharge, but nitrazine testing is typically positive. Educational objective: Cervical insufficiency is a structural weakness of the cervix that causes spontaneous, painless cervical dilation and potential second-trimester pregnancy loss. Patients typically present with mild symptoms (eg, increased vaginal discharge, light vaginal bleeding, pelvic pressure); on examination, bulging amniotic membranes may be seen. References: Overview of cervical insufficiency: diagnosis, etiologies, and risk factors. (http://www.ncbi.nlm.nih.gov/pubmed/27015229) ACOG practice bulletin no. 142: cerclage for the management of cervical insufficiency. (http://www.ncbi.nlm.nih.gov/pubmed/24451674)

A 32-Year-Old Primigravid Woman at 21 Weeks Gestation Comes to the Office