Preterm labor
Background
- Defined as labor before 37 weeks (uterine contraction and cervical change)
- Increased risks to child depending on age of fetus
- Cerebral palsy, poor lung development, cognitive delay, etc
- Can be triggered by infections, stress, hypertension, uncontrolled DM
Clinical Features
- Similar to term labor
- Uterine contractions q 10 min (may be irregular)
- New onset of vaginal mucus, blood, pink discharge, amniotic fluid
- Low back ache, vaginal pressure
Differential Diagnosis
Vaginal Bleeding in Pregnancy (>20wks)
- Emergent delivery
- Placental abruption
- Placenta previa
- Vasa previa
- Uterine rupture
- Preterm labor
- Vaginal trauma
- Placenta accreta
- Intrauterine fetal demise
Evaluation
- Type and Screen, CBC, Chem 10, Coags, U/A with culture, Utox (cocaine increases risk of abruption)
- Do NOT perform digital exam in patients who present with vaginal bleeding when >20 weeks pregnant due to potential for placenta previa
- Start with ultrasound to assess position of cervix and rule out placenta previa
- Swabs for nitrazine, fetal fibronectin (FFN), GBS culture should also precede digital exam
- Some lubricants can affect FFN and amniotic fluid pH strip
- Nitrazine test (5% FP rate, 1% FN rate) - pH swab turns blue, indicating alkalotic amniotic fluid (pH 6.5 - 7.5 positive test); do not touch to mucous plug in cervix[1]
- Proceed with digital exam if placental previa unlikely, and digital exam is urgently needed to assist patient care, such as in fetal HR decels
Management
- IV access x2, ABCs
- Fetal heart monitor
- Immediate obstetrical consult
Cervical length
- >30mm - Labor less likely
- Observation of 6 hours might be appropriate
- 20-30mm - Increased risk for preterm labor
- Fetal fibronectin result can assist, if over 50ng/ml manage labor actively
- <20mm - labor very likely
- Manage actively
Management by Weeks
- 24-32 weeks
- Magnesium sulfate (neuroprotection against cerebral palsy)
- <34 weeks
- Hospitalization
- Betamethasone 12mg IM q24hrs x2 doses
- Tocolytics (see below for options/dosages)
- Antibiotics for GBS prophylaxis if status unknown
- Other antibiotics only indicated in setting of active infection
- 34-36 weeks
- A single course of betamethasone is recommended to those who have not received a previous course [2]
Tocolysis
Indications
- Only if fetus would benefit from delay in delivery of 48 hrs
- Gestational age 22wks - 34 wks
- Transport to facility for definitive delivery
- Delay in delivery for treatment of reversible condition possibly triggering labor (UTI/pyelo)
- Betamethasone requires approximately 48 hrs for maximal benefit for lung maturity, reducing intraventricular hemorrhage, NEC, and death
- Tocolysis rarely effective for longer than 48 hrs
- Does not remove underlying cause for tocolysis
Contraindications
- Intrauterine fetal demise / lethal anomaly
- Maternal hemorrhage or instability
- Intraamniotic infection
- Severe preeclampsia or eclampsia
- Nonreassuring fetal status
- Contraindications to the drugs
Medications
- Indomethacin 50-100mg loading dose, 25mg q4-6 hrs for 48 hrs. (avoid in gestation >32 weeks for concern of premature narrowing or closure of the ductus arteriosus)
- Nifedipine 20mg x1, additional 20mg dose in 90min if ctx persist, followed by 20mg q3-8 hrs PRN ctx
- Terbutaline 0.25mg sq q20-30 min up to 4 doses PRN ctx
Disposition
- Admission to OB floor for delivery, or transfer to facility to manage delivery
- If cervix >30mm, contractions have stopped, consider 6 hours of obs
See Also
External Links
References
- ↑ Nitrazine Test. https://www.pathology.med.umich.edu/poc/onsite/pH-amniotic.html
- ↑ https://www.acog.org/clinical/clinical-guidance/committee-opinion/articles/2017/08/antenatal-corticosteroid-therapy-for-fetal-maturation#:~:text=A%20single%20course%20of%20betamethasone,previous%20course%20of%20antenatal%20corticosteroids.
- UpToDate "Overview of preterm labor and birth"
- UpToDate "Inhibition of acute preterm labor"