Preterm Delivery — USMLE Step 2 CK Guide

Flashcards covering vocabulary and key concepts related to preterm delivery and its management.

Preterm labor

Onset of regular uterine contractions causing cervical change (dilation/effacement) before 37 weeks gestation.

Key risk factors for preterm delivery

History of prior preterm delivery, short cervical length (<2.5 cm), infections, smoking, substance use, uterine anomalies, multifetal gestation, low maternal BMI, vaginal bleeding.

Tocolytics

Medications used to delay preterm labor.

Gestational age assessment <24 weeks

No tocolytics, offer palliative care if imminent delivery.

Tocolytics for 24–34 weeks

Use to delay labor, administer antenatal corticosteroids and magnesium sulfate for neuroprotection.

Indomethacin

1st-line tocolytic if <32 weeks, a COX inhibitor.

Nifedipine

1st-line tocolytic if 32–34 weeks, a calcium channel blocker.

Terbutaline

A beta-agonist used as a tocolytic, can cause tachycardia and pulmonary edema.

Contraindications to tocolytics

Includes chorioamnionitis, severe preeclampsia, non-reassuring fetal status, significant vaginal bleeding, fetal demise.

Chorioamnionitis

Condition requiring immediate delivery regardless of gestational age.

Fetal fibronectin testing

Used to assess the risk of preterm delivery between 22–34 weeks.

Preventive therapy for prior preterm birth

Weekly IM 17α-hydroxyprogesterone caproate.

Cervical length <2.5 cm

Considered short and indicates a higher risk for preterm delivery.

Positive fetal fibronectin test

Indicates a higher risk of preterm delivery.

Management of chorioamnionitis

Immediate delivery and IV antibiotics (Ampicillin + Gentamicin).

Definition of preterm labor

Regular uterine contractions plus cervical change before 37 weeks.

Common differentials for preterm labor

Includes placental abruption, cervical insufficiency, and preterm premature rupture of membranes (PPROM).