Order: Pitocin 25 U IM now.

Available: Pitocin 100 U in a 10 ml vial.

How much will you draw up for one dose? (Provide the number only, no units of measurement.)

Choice A rationale

An ultrasound for cervical length is a crucial diagnostic tool for assessing preterm labor. A shortened cervix, typically less than 2.5 cm, is a significant risk factor for preterm birth. Measuring the cervical length helps to determine the probability of progressing to true labor and guides subsequent interventions, such as cerclage or progesterone therapy.

Choice B rationale

Amniocentesis, the sampling of amniotic fluid, is primarily used for genetic testing, assessing fetal lung maturity, or diagnosing fetal infection. It is not a standard procedure for a patient with intermittent back pain and pelvic pressure at 28 weeks gestation, as it carries risks, including inducing labor and infection, and isn't the first-line diagnostic for this presentation.

Choice C rationale

A glucose tolerance test is a screening tool for gestational diabetes, typically performed between 24 and 28 weeks of gestation. While the patient is at this gestational age, the test is not directly related to the symptoms of back pain and pelvic pressure, which are more indicative of potential preterm labor. The test wouldn't be a priority in this specific context.

Choice D rationale

A fetal fibronectin (fFN) swab is a diagnostic test used to predict the likelihood of preterm birth. The presence of fFN, a protein that acts as a "glue" for the fetal sac, in cervical or vaginal secretions between 22 and 34 weeks gestation suggests an increased risk of preterm labor within the next one to two weeks. It is a key tool in managing preterm labor.

Choice E rationale

Encouraging fluids and rest is a common initial intervention for a patient with symptoms of preterm labor. Dehydration can sometimes trigger uterine contractions, so rehydration may help to stop them. Resting can also reduce uterine irritability. This non-pharmacological approach is often the first step before more aggressive treatments are considered. *.

Step 1: The total units available are 100 U in a 10 mL vial.

Step 2: Calculate the concentration of the medication: 100 U ÷ 10 mL = 10 U/mL.

Step 3: The ordered dose is 25 U.

Step 4: Calculate the volume to administer: 25 U ÷ (10 U/mL) = 2.5 mL. Final calculated answer: 2.5.