Complications of Labor and Delivery

• Preterm labor (PTL)


  Labor that occurs before week 37
• Preterm labor


  • Many patients present with preterm contractions, but only those who have cervical change are diagnosed
  • Differs from cervical insufficiency which is a silent, painless dilation and effacement of the cervix
  • Both can result in preterm delivery
• Preterm delivery is the leading cause of fetal morbidity and mortality in the United States
• The incidence of preterm delivery in the United States reached a peak in 2005 to more than 12% of all births, which is higher than that in 2000 where the rate was 11.6%
• Although since 2006 the preterm birth rate has declined, it is still higher than that in 2000
• Approximately a half of a million babies are born preterm each year, though only approximately 80,000 of these are before 32 weeks' gestation
• Preterm delivery


  Infants born before 37 weeks' gestation
• Low-birth-weight (LBW) infants


  Infants born weighing less than 2,500 g
• Intrauterine growth restriction (IUGR) or small for gestational age (SGA)


  Infants who have not grown appropriately for their gestational age
• An IUGR infant can be born after week 37 but still be LBW
• Morbidity and mortality of preterm infants

  • Dramatically affected by gestational age and birth weight
  • Prematurity puts infants at increased risk of respiratory distress syndrome, intraventricular hemorrhage, sepsis, and necrotizing enterocolitis
  • Infants born on the cusp of viability at 24 weeks' gestation have a greater than 50% mortality rate, whereas infants born after week 34 have a mortality rate that is only slightly higher than that of full-term neonates
• Risk factors for preterm labor

  • Preterm rupture of membranes
  • Chorioamnionitis
  • Multiple gestations
  • Uterine anomalies such as a bicornuate uterus
  • Previous preterm delivery
  • Maternal prepregnancy weight less than 50 kg
  • Placental abruption
  • Maternal disease including preeclampsia, infections, intra-abdominal disease or surgery
  • Low socioeconomic status
• Tocolysis


  The attempt to prevent contractions and the progression of labor
• Many tocolytics are used in the United States, but only ritodrine-a beta-mimetic agent-is FDA approved for this purpose
• It is difficult to conduct placebo-controlled studies of new tocolytics because most patients and clinicians are unwilling to allow contractions to proceed without some tocolytic therapy
• Studies have demonstrated that tocolytics prolong gestation for only 48 hours
• The principal benefit from gaining 48 hours in a pregnancy

  To allow treatment with steroids to enhance fetal lung maturity and reduce the risk of complications associated with preterm delivery
• Betamethasone, a glucocorticoid, has been shown to reduce the incidence of respiratory distress syndrome and other complications from preterm delivery
• There are many situations in which preterm labor should be allowed to progress, such as chorioamnionitis, nonreassuring fetal testing, and significant placental abruption
• With many other issues such as maternal disease—particularly preeclampsia or poor placental perfusion-an assessment of the severity of the situation, the precipitous nature of the complication, and the risks from prematurity all contribute to the decision of whether or not to tocolyze
• The goal of a tocolytic

  To decrease or halt the cervical change resulting from contractions
• Hydration


  Can often decrease the number and strength of contractions in the case of preterm contractions without cervical change
• Antidiuretic hormone (ADH)


  The octapeptide synthesized in the hypothalamus along with oxytocin, which may bind with oxytocin receptors and lead to contractions
• Beta-mimetics


  Increase the level of cAMP, which sequesters calcium in the sarcoplasmic reticulum, causing a decrease in uterine contractions
• Beta-mimetics


  • The two historically used for preterm labor are ritodrine and terbutaline
  • Randomized controlled studies showed they increased gestation an average of only 24 to 48 hours further over hydration and bed rest alone
  • Side effects include tachycardia, headaches, anxiety, pulmonary edema, and in rare cases, maternal death
• Magnesium sulfate


  Decreases uterine tone and contractions by acting as a calcium antagonist and a membrane stabilizer
• In small placebo-controlled trials, magnesium has not been shown to change gestational age of delivery, and in larger trials, its efficacy did not vary significantly from that of beta-mimetics
• Magnesium sulfate


  • Side effects include flushing, headaches, fatigue, and diplopia
  • At toxic levels (> 10 mg/dL), respiratory depression, hypoxia, and cardiac arrest have been seen
  • Deep tendon reflexes are depressed at magnesium levels less than 10 mg/dl
• Calcium channel blockers


  Decrease the influx of calcium into smooth muscle cells, thereby diminishing uterine contractions
• Calcium channel blockers


  • Nifedipine has been the principal drug studied, and it seems to have comparable efficacy to that of ritodrine and magnesium
  • Side effects include headaches, flushing, and dizziness
• Prostaglandin inhibitors


  Decrease the intracellular levels of calcium and enhance myometrial gap junction function, thereby decreasing myometrial contractions
• Indomethacin


  • An NSAID that blocks the enzyme cyclooxygenase and decreases the level of prostaglandins, used as a tocolytic
  • Has been shown to effectively decrease contractions and forestall labor with minimal maternal side effects
  • But has been associated with fetal complications like premature constriction of the ductus arteriosus, pulmonary hypertension, and oligohydramnios
• Indomethacin is most commonly used before 32 weeks' gestation and generally only for 48 to 72 hours
• If indomethacin is used, the amniotic fluid index should be checked prior to initiating the drug, and again after 48 hours, to monitor for development of oligohydramnios
• Oxytocin antagonists


  Have been studied as tocolytics, but clinical studies have been small and have not demonstrated an improvement in outcomes
• Preterm rupture of membranes (PROM)

  Rupture of membranes occurring before week 37
• Premature rupture of membranes (PROM)

  Rupture of membranes occurring before the onset of labor
• Preterm premature rupture of membranes (PPROM)


  When preterm rupture of membranes and preterm labor occur together
• Prolonged rupture of membranes

  Anytime rupture of membranes lasts longer than 18 hours before delivery
• Without intervention, approximately 50% of patients who have preterm rupture of membranes will go into labor within 24 hours and up to 75% will do so within 48 hours