9 - Complications of Labor and Delivery

Preterm labor (PTL)

Labor before week 37

• Cervical change upon examination with contractions OR

• Regular contractions + ≥2cm dilatation

Diagnosis of preterm labor is established if there is/are

20 to <26 weeks AOG

AOG considered as the previable period

Group B streptococcus (GBS)

Bacteria that has the unique ability to synthesize hyaluronan-degrading enzyme hyaluronidase infection leads to loss of hyaluronan in cervical epithelium

Ascending infection with bacteria from the vagina and cervix

Most common entry route of bacteria to the gestational unit

Previous preterm delivery

Greatest risk factor for preterm labor

Progesterone

Withdrawal of this hormone may trigger parturition

• 17-alpha-hydroxyprogesterone caproate (17-OHP) 250 mg IM weekly from 16-36 weeks AOG

• Micronized progesterone 20 mg per vagina from 24-34 weeks AOG

Progesterone regimens for preterm birth prevention

• Extremely preterm (< 28 weeks)

• Very preterm (28 to < 32 weeks)

• Moderate to late preterm (32 to < 37 weeks)

Classifications of preterm infants

• Low birth weight (LBW) 1500 - 2500 g

• Very LBW 1000 - 1500 g

• Extremely LBW 500 - 1000 g

Classification of infants by birth weight

· Betamethasone 12mg IM q24 for 2 doses

· Dexamethasone 6mg IM q12 for 4 doses

Corticosteroid regimens for fetal lung maturation

Between 24 – 34 weeks, up until 36 6/7 weeks

When do we give corticosteroids in preterm labor?

Delay delivery by at least 48 hours

The goal of giving tocolytics in preterm labor is to:

• Chorioamnionitis

• Non-reassuring fetal testing

• Significant placental abruption

Indications for emergent delivery in preterm labor

· Dehydration increases levels of vasopressin or antidiuretic hormone (ADH) → bind to oxytocin receptors→contractions

· Hydration decreases ADH levels → decrease contractions

How does hydration reduce contractions?

Calcium channel blockers decrease calcium influx into smooth muscle cells →diminished uterine contractions

How do calcium channel blockers reduce contractions?

• Prostaglandins increase intracellular calcium level and myometrial gap junction function →increase myometrial contractions

• Anti-prostaglandin agents inhibit contractions and may halt labor

How do prostaglandin inhibitors reduce contractions?

blocks cyclooxygenase→ decreases level of prostaglandins

How does indomethacin (NSAID) reduce contractions?

Decreases uterine tone and contractions by acting as calcium antagonist and membrane stabilizer

How does magnesium sulfate reduce contractions?

· Myosin light-chain kinase (MLK) regulates contraction, which is activated by calcium ions–calmodulin interaction

· Increased cAMP level→calcium sequestered in sarcoplasmic reticulum →decreased free calcium ions and uterine contractions

· Increased β-agonists→ convert ATP to cAMP →activate β2 receptors on myometrial cells

How do beta-mimetics reduce contractions?

· Selective oxytocin–vasopressin receptor antagonists, theoretically effective tocolytic with minimal side effects

· Small clinical studies with no improvement in outcomes

How do oxytocin antagonists reduce contractions?

Preterm rupture of membranes

Spontaneous rupture of fetal membranes before week 37: common cause of PTL, preterm delivery, and chorioamnionitis

• ~50% ROM within 24 hours

• ≤ 75% within 48 hours

How many percent of ROM patients lead to labor within 24 and 48 hrs?

Premature rupture of membranes (PROM)

ROM before onset of labor; presents the most significant risk of development of chorioamnionitis (risk increases with length of ROM)

Preterm premature rupture of membranes (PPROM)

Both preterm and premature rupture of membranes occur

Prolonged rupture of membranes

ROM lasting >18 hours before delivery

• Ampicillin + erythromycin IV followed by erythromycin + amoxicillin (oral) OR

• Azithromycin (oral) once + IV ampicillin + amoxicillin (oral)

Recommended antibiotic regimen for PPROM <34 weeks AOG

Fever

(temperature ≥39 deg C)

Only reliable indicator for diagnosis of chorioamnionitis

Deliver, give GBS proxphylaxis as needed

Management for PROM ≥37 weeks AOG

Expectant management, corticosteroids, GBS prophylaxis, among others

Management of PROM 24 to <34 weeks AOG