Preterm Labor Flashcards
1
Q
Physiology/pathophysiology of preterm labor and preterm premature rupture of membranes (PPROM)
A
- Multifactoral, complex process, not well understood.
- Cervix undergoes considerable change, including collagen remodeling and altered cellular content→ effacement and dilatation
- 4 main pathways to cervical change
- Premature activation of the maternal or fetal HPA axis → release of prostaglandins and stimulation of placental estrogens related to myometrium activation and labor.
- Pathological uterine distention—Both multifetal gestation and polyhydramnios → increase the formation of gap junctions and oxytocin receptors → contractions.
- Inflammation— systemic infection or ascending genital tract infections → inflammatory response → prostaglandin production → break down the extracellular matrix of the fetal membranes and cervix.
- Decidual hemorrhage → release of thrombin → promotion of inflammation-associated PTB mechanisms.
2
Q
Define preterm birth
A
Birth sometime between 20 weeks - 37 weeks
*don’t round up
3
Q
High risk for preterm birth
A
Demographics
- <17 or >35 years
- Less education (<12 years)
- Single marital status
- Lower socioeconomic status
- Short interpregnancy interval (<18 months)
Prior obstetric/gynecological history
- Prior history of PTB
- strongest risk factor
- Cervical surgery(cone biopsy, LEEP, etc.)
- Multiple cervical dilation and uterine evacuations
- Uterine anomalies
Nutritional status/physical activity
- Prepregnancy BMI <19 or weight <50kg
- Poor nutritional status
- Long working hours (>80h/week)
- Hard physical labor (including standing >8 hours)
Current pregnancy characteristics
- Assisted reproductive techniques
- Multiple gestation - one of the strongest risks
- Fetal disease
- Congenital malformations
- Poly- or oligohydramnios
- Maternal medical condition (e.g., hypertension, diabetes, thyroid disease, and asthma)
- Maternal abdominal surgery
- Psychological factors (e.g., stress, depression)
- Substance abuse, smoking
- Infection - BV, UTI, STDs
- BV associated with 2x risk of PTB
- Short cervical length between 14 and 28 weeks Positive fetal bronectin between 22 and 34 weeks
4
Q
Fetal fibronectin testing (fFN)
A
- Glycoprotein found in high concentrations in amniotic fluid and the interface between the decidua and trophoblast cells
- Thought to play a role in implantation/maintenance of the attachment btw deciduas and fetal chorion
- Normally in the cervical and vaginal secretions before 16–20 weeks’ gestation, abnormal after 20 weeks, except as a marker of the imminent onset of labor at term.
- Positive test modestly useful in predicting the risk of a PTB occurring within 1–2 weeks
- Negative result more strongly predictive of no PTB (>90% negative predictive value)
- Dont do fFN if: bleeding, ROM, coitus, digital exam, or vaginal ultrasound within 24 hours
- False neg – lube, soap, disinfectants inside vag
5
Q
Cervical length measurement
A
- Measured by transvaginal ultrasound
- Effective screening tool to predict PTB
- Decreasing cervical length is associated with increased risk of PTB.
- A short cervical length <25 mm in the early or late 2nd tri → marked increased risk of PTB
- False positives
- No utility in preventing PTB
- Increased predictive power of both tests when used in combo with fFN
6
Q
Symptoms of preterm labor
A
- Menstrual- like cramps or regular contractions
- “Baby balling up”
- Low backache
- near tailbone more concerning
- Diarrhea, urinary frequency - soft signs
- Sensation of pelvic pressure or thigh pain
- Sudden increase/change in vaginal discharge
- Intermittend lower abdominal pain
7
Q
Evaluation preterm labor and PPROM
A
- Decision to admit/discharge/transport should be made within 4 hours
- Evaluate uterus, assess size/contractions
- Thorough hx/OLDCARTS
- Sterile speculum exam → get swab for fFN in posterior fornix
- Must get this first to be valid
- pH – amniotic fluid is very alkaline
- Look for ferning on dry slide
- Look for pooling in posterior fornix – if you don’t see it, have pt valsalva/cough
- GC/CT cultures, GBS strep (outter 1/3 of vag and rectal area)
- Cervical exam - avoid if ROM (might be able to gauge from spec exam
- Abd u/s look for placental position, EFW, etc
- If ROM confirmed OR cervix > 3cm → hospitalize
- If intact membranes and cervix < 3 cm → send fFN
8
Q
Cervical exam findings and decision for tocolysis
A
(Kim’s lecture)
- >3 cm dilated, 80% effaced → PTL dx confirmed → tocolysis
- 2-3 cm dilated, < 80% → “iify” → observe, repeat exam in 1-2 hrs, look at cervical length, fFN
- < 2 cm or < 80 effaced → dx uncertain → watch for cervical change
- Cervical length < 20 mm concerning
- Cervical U/S → large role in evaluating PTL
- 20 – 30 mm: index of suspicion
- > 30 mm: PTL unlikely
9
Q
Preterm labor treatment
A
- Common tocolytics
- Magnesium sulfate – loading dose: 4-6 grams then 1-4 grams/hr → blocks neuromuscular transmission → blocks contractions
- Flushing, warmth, dry mouth , drowsy.
- Check reflexes (first thing that diminishes with mag toxicity) and possible mag levels
- Usually MD managed
- Watch Urine output (risk of cardiac arrest)
- Terbutiline (trade name: Brethine)
- Not really used anymore due to maternal/fetal tachycardia and cardiac arrest
- Doesn’t work well in terms of long term tocolysis
- Procardia/nefedipine – Ca channel blocker
- Magnesium sulfate – loading dose: 4-6 grams then 1-4 grams/hr → blocks neuromuscular transmission → blocks contractions
- Single course of steroids given before 32 weeks (2 doses) → reduces risk of RDS and IVH
- Bedrest – studies don’t show it to be effective
- Not totally benign → deconditions muscles
- Recommend modified activity or pelvic rest (no orgasm)
10
Q
Modifiable Risk Factors
A
- Cigarette smoking – PTL, FGR
- Substance abuse – esp cocaine
- Infections – ie UTI, genital infection
- High levels of stress, inadequate social support – unsure of exact mechanism
11
Q
Methods of preterm labor prevention:
Weight and nutrition
A
- Underweight before pregnancy → doubles risk of PTB
- Calcium, iron, and omega-3 fatty acids important
- Need 200-300mg omega 3s daily or eat fish 2-3x per week
- Adequate iron stores
- Healthy, well balanced diet of 3 meals/day + 2 snacks
12
Q
Preterm birth prevention
A
- Mitigate modifiable risk factors:
- Adquate weight and nutrition
- Smoking cessation
- one of the most important measures
- Reducing infection
- Avoiding cocaine
- Avoiding a short (<18 months) interpregnancy interval
- Dx and tx of asymptomatic bacteriuria
- Improving sleep quality and reducing fatigue
- Prolonged standing and working > 40 hours/week associated with PTB
- Progesterone
- Cerclage
13
Q
Preterm birth prevention:
Progesterone therapy
A
- May inhibit prostaglandins and ability of uterus to contract
- Hx of prior PTB: 250mg IM 17-hydroxyprogesterone caproate from weeks 16 through term in a singleton pregnancy
- Short cervix: Vaginal progesterone 100 mg if no prior spontaneous PTB and cervical length of 20mm or less at 24 weeks’ gestation or earlier.
- REFER/COMANAGE
14
Q
Who should be evaluated for cerclage?
A
- Prior history of cervical trauma such as conization or LEEP procedures
- Progressively earlier births
- 2 or more consecutive prior second-trimester pregnancy losses, or three or more early (<34 weeks) PTBs
- Offer if: prior PTD and cervix length < 15-24mm at < 24 weeks
- Consider transabdominal cerclage if suspected cervical insufficiency who have had unsuccessful cerclages before
15
Q
Diagnostic of preterm labor
A
- Documented regular UC ≥6/hour
AND
- At least one of the following:
- Rupture of membranes
- Cervical change
- Cervix 2 cm dilated or 80% effaced
If criteria not met → false labor.
