lecture 9 preterm and postterm delivery n.
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  3. DEFINITION OF TERMS I. AS TO SIZE Small-for-gestational age / fetal growth restriction / intrauterine growth restriction (SGA/IUGR) newborns with birthweight below the 10th percentile for gestational age Large-for-gestational age (LGA) birthweight above the 90th percentile Appropriate-for-gestational age (AGA) newborns with weight between the 10th and 90th percentiles II. AS TO AOG Preterm or premature birth neonates born too early delivery before 37 completed weeks Term 37 – 42 weeks Post term > 42 weeks

  4. Medical and Obstetrical Complications Preeclampsia Fetal distress Fetal growth restriction Placental abruption Fetal death Spontaneous preterm labor with or without prematurely ruptured membranes CAUSES OF PRETERM BIRTH

  5. II. Threatened Abortion Vaginal bleeding or spotting is associated with increased incidence of subsequent pregnancy loss prior to 24 weeks, preterm labor, and placental abruption CAUSES OF PRETERM BIRTH

  6. III. Lifestyle Factors 1. Cigarette smoking Associated with 20 % of low-birthweight neonates, 8 % of preterm births, and 5 % of perinatal deaths 2- to 5-fold risk of preterm prematurely ruptured membranes, a 1.2- to 2-fold risk of preterm delivery, and a 1.5- to 3.5-fold risk of fetal growth restriction increased incidence of ectopic pregnancy, placental abruption, and placenta previa CAUSES OF PRETERM BIRTH

  7. 2. inadequate maternal weight gain during pregnancy 3. illicit drug 4. Other maternal factors: young or advanced maternal age poverty short stature vitamin C deficiency occupational factors: prolonged walking or standing, strenuous working conditions, and long weekly work hours CAUSES OF PRETERM BIRTH

  8. 5. Psychological and physical stress - seldom been formally studied but seem intuitively important 6. Both stress and higher levels of maternal serum cortisol have been associated with spontaneous preterm birth 7. significant link between low birthweight and preterm birth in women injured by physical abuse 8. maternal depression was not associated with birth prior to 35 weeks CAUSES OF PRETERM BIRTH

  9. IV. Genetic Factors  gene for decidual relaxin is one candidate Fetal mitochondrial trifunctional protein defects or polymorphism in the interleukin-1 gene complex, 2-adrenergic receptor, or tumor necrosis factor- α (TNF- α) may also be involved in preterm membrane rupture CAUSES OF PRETERM BIRTH

  10. V. Chorioamnionitis Infection of the membranes and amnionic fluid caused by a variety of microorganisms - possible causes of ruptured membranes, preterm labor, or both recovery of organisms from the chorioamnion was significantly increased with spontaneous preterm labor CAUSES OF PRETERM BIRTH

  11. Risk-Scoring Systems Not effective 2. Prior Preterm Birth strongly correlates with subsequent preterm labor risk of recurrent preterm delivery for women whose first delivery was preterm was increased threefold compared with that of women whose first neonate was born at term More than a third of women whose first two newborns were preterm subsequently delivered a third preterm newborn IDENTIFICATION OF WOMEN AT RISK FOR SPONTANEOUS PRETERM LABOR

  12. 3. Incompetent Cervix recurrent, painless cervical dilatation and spontaneous midtrimester birth in the absence of spontaneous membrane rupture, bleeding, or infection 4. Cervical Dilatation Asymptomatic cervical dilatation after midpregnancy has gained attention as a risk factor for preterm delivery, although some clinicians consider it to be a normal anatomical variant, particularly in parous women Recent studies suggested that parity alone is not sufficient to explain cervical dilatation discovered early in the third trimester IDENTIFICATION OF WOMEN AT RISK FOR SPONTANEOUS PRETERM LABOR

  13. ULTRASONOGRAPHIC MEASUREMENT OF CERVICAL LENGTH mean cervical length at 24 weeks was about 35 mm, and those women with progressively shorter cervices experienced increased rates of preterm birth women with a previous preterm birth (< 32 weeks) should undergo, on her next pregnancy, an ultrasound examination of cervical length between 16 to 24 weeks AOG; a shortened cervix ( < 25mm ) correlates with another subsequent preterm birth before 35 weeks

  14. the value of cervical length to predict birth before 35 weeks is apparent only in women at high risk for preterm birth routine cervical ultrasonography currently has no role in the screening of normal-risk pregnant women efficacy of cerclage for women with only a shortened cervical length with no history of recurrent midpregnancy loss is inconclusive ULTRASONOGRAPHIC MEASUREMENT OF CERVICAL LENGTH

  15. 5. Signs and Symptoms painful or painless uterine contractions pelvic pressure menstrual-like cramps watery vaginal discharge pain in the low back IDENTIFICATION OF WOMEN AT RISK FOR SPONTANEOUS PRETERM LABOR

  16. 6. Ambulatory Uterine Monitoring an external tocodynamometer is belted around the abdomen and connected to an electronic waist recorder Uterine activity is transmitted via telephone daily Women are educated concerning signs and symptoms of preterm labor, and clinicians are kept apprised of their progress ACOG concluded that the use of this expensive, bulky, and time-consuming system does not reduce the rate of preterm birth IDENTIFICATION OF WOMEN AT RISK FOR SPONTANEOUS PRETERM LABOR

  17. 7. Fetal Fibronectin glycoprotein produced in 20 different molecular forms by hepatocytes, fibroblasts, and endothelial cells, and by fetal amnion Present in high concentrations in maternal blood and in amnionic fluid which play a role in intercellular adhesion during implantation and in the maintenance of placental adhesion to the decidua detected in cervicovaginal secretions in women who have normal pregnancies with intact membranes at term, and it appears to reflect stromal remodeling of the cervix prior to labor IDENTIFICATION OF WOMEN AT RISK FOR SPONTANEOUS PRETERM LABOR

  18. 7. Fetal Fibronectin fibronectin detection in cervicovaginal secretions prior to membrane rupture was a possible marker for impending preterm labor measured using an enzyme-linked immunosorbent assay values exceeding 50 ng/mL are considered positive positive value for cervical or vaginal fetal fibronectin assay, as early as 8 to 22 weeks - powerful predictor of subsequent preterm birth IDENTIFICATION OF WOMEN AT RISK FOR SPONTANEOUS PRETERM LABOR

  19. 8. Bacterial Vaginosis not an infection, a condition in which the normal, hydrogen peroxide–producing lactobacillus-predominant vaginal flora is replaced with anaerobes, Gardnerella vaginalis, Mobiluncus species, and Mycoplasma hominis associated with spontaneous abortion, preterm labor, preterm ruptured membranes, chorioamnionitis, and amnionic fluid infection may precipitate preterm labor by a mechanism similar to that proposed for amnionic fluid infection screening and treatment have not been shown to prevent preterm birth IDENTIFICATION OF WOMEN AT RISK FOR SPONTANEOUS PRETERM LABOR

  20. 9. Lower Genital Tract Infection Currently, screening and treatment to prevent preterm birth in women with either Chlamydia trachomatis or Trichomonas vaginalis is not recommended IDENTIFICATION OF WOMEN AT RISK FOR SPONTANEOUS PRETERM LABOR

  21. 10. Salivary Estriol increased maternal salivary estriol concentration and subsequent preterm birth 11. Periodontal Disease Oral bacteria - Fusobacterium nucleatum and Capnocytophaga species, have been associated with upper genital tract infection in pregnant women sevenfold risk of preterm birth IDENTIFICATION OF WOMEN AT RISK FOR SPONTANEOUS PRETERM LABOR




  25. MANAGEMENT OF PRETERM LABOR I. PRETERM RUPTURED MEMBRANES A history of vaginal leakage of fluid should prompt a sterile speculum examination to visualize gross vaginal pooling of amnionic fluid, clear fluid from the cervical canal, or both Confirmation by ultrasonographic examination to assess amnionic fluid volume; to identify the presenting part; and if not previously determined, to estimate gestational age

  26. After confirmation of ruptured membranes, the following steps are taken: Cervical dilatation and effacement are estimated visually during a sterile speculum examination 2. If < 34 weeks, if there are no maternal or fetal indications for delivery, the woman and her fetus are initially observed in the labor unit. Broad-spectrum parenteral antimicrobials are begun to prevent chorioamnionitis. Fetal heart rate and uterine activity are monitored for cord compression, fetal compromise, and early labor. MANAGEMENT OF PRETERM LABOR

  27. 3. If < 34 weeks, betamethasone (two 12-mg doses intramuscularly 24 hours apart) or dexamethasone (6 mg intramuscularly every 12 hours for four doses) is given 4. If the fetal status is reassuring, and if labor does not ensue, the woman is usually transferred to an antepartum unit and observed for labor, infection, or fetal jeopardy MANAGEMENT OF PRETERM LABOR

  28. For pregnancies 34 weeks or beyond, if labor does not begin spontaneously, then it is induced with intravenous oxytocin unless contraindicated. Cesarean delivery is performed for usual indications, including failed induction of labor During labor or induction, a parenteral antimicrobial is given for prevention of group B streptococcal infection MANAGEMENT OF PRETERM LABOR

  29. PRETERM LABOR WITH INTACT FETAL MEMBRANES Diagnosis Criteria to document preterm labor: Contractions of four in 20 minutes or eight in 60 minutes plus progressive change in the cervix Cervical dilatation greater than 1 cm Cervical effacement of 80 percent or greater MANAGEMENT OF PRETERM LABOR

  30. PRETERM LABOR WITH INTACT FETAL MEMBRANES managed the same as for those with preterm ruptured membranes The cornerstone of treatment is to avoid delivery prior to 34 weeks, if possible Amniocentesis to detect infection (not usually indicated) Steroid therapy to enhance fetal lung maturation Thyrotropin-Releaasing hormone for fetal lung maturation 4. Antenatal Phenobarbital and Vitamin K – combination is not recommended for the prevention of neonatal intraventricular hemorrhage MANAGEMENT OF PRETERM LABOR

  31. INTERVENTIONS TO DELAY PRETERM BIRTH Antimicrobials – not recommended for the sole purpose of preventing delivery 2. Emergency cerclage 3. Treatment for bacterial vaginosis

  32. INHIBITION OF PRETERM LABOR Bed rest 2. Hydration and sedation 3. Beta adrenergic receptor agonist Ritodrine Terbutaline, Isoxuprine Beta adrenergic drugs Parenteral beta agonists prevent preterm birth for at least 48 hours facilitating maternal transport and giving of steroids

  33. 4. Magnesium sulfate Ionic magnesium in a sufficiently high concentration can alter myometrial contractility role is presumably that of a calcium antagonist Clinical observations are that magnesium in pharmacological doses may inhibit labor intravenously administered magnesium sulfate—a 4-g loading dose followed by a continuous infusion of 2 g/hr—usually arrests labor 5. Prostaglandin inhibitors (ex. Indomethacin) 6. Calcium channel blockers Nifedipine 7. Atosiban (oxytocin antagonist) 8. Nitric oxide donors (nitroglycerin) – not effective INHIBITION OF PRETERM LABOR

  34. The following considerations should be given to women in preterm labor: Confirmation of preterm labor 2. For pregnancies less than 34 weeks in women with no maternal or fetal indications for delivery, close observation with monitoring of uterine contractions and fetal heart rate is appropriate, and serial examinations are done to assess cervical changes 3. For pregnancies less than 34 weeks, glucocorticoids are given for enhancement of fetal lung maturation RECOMMENDED MANAGEMENT OF PRETERM LABOR

  35. The following considerations should be given to women in preterm labor: 4. For pregnancies less than 34 weeks in women who are not in advanced labor, some practitioners believe it is reasonable to attempt inhibition of contractions to delay delivery while the women are given glucocorticoid therapy and group B streptococcal prophylaxis 5. For pregnancies at 34 weeks or beyond, women with preterm labor are monitored for labor progression and fetal well-being 6. For active labor, an antimicrobial is given for prevention of neonatal group B streptococcal infection RECOMMENDED MANAGEMENT OF PRETERM LABOR

  36. Labor Continuous electronic monitoring is preferred Fetal tachycardia, especially with ruptured membranes, is suggestive of sepsis Intrapartum acidemia may intensify some of the neonatal complications usually attributed to preterm delivery 2. Prevention of neonatal group B Streptococcal infections The American College of Obstetricians and Gynecologists, recommend either penicillin G or ampicillin intravenously every 6 hours until delivery for women in preterm labor INTRAPARTUM MANAGEMENT

  37. 3. Delivery Staff proficient in resuscitative techniques commensurate with the gestational age of the newborn and fully oriented to any specific problems should be present 4. Prevention of neonatal intracranial hemorrhage Preterm newborns have germinal matrix bleeding that can extend to more serious intraventricular hemorrhage It was hypothesized that cesarean delivery to obviate trauma from labor and vaginal delivery might prevent these complications This has not been validated by most subsequent studies hemorrhages related to whether or not the fetus had been subjected to the active phase of labor, defined as the interval before 5 cm cervical dilatation avoidance of active-phase labor is impossible in most preterm births because the route of delivery cannot be decided until the active phase labor is firmly established INTRAPARTUM MANAGEMENT


  39. DEFINITION OF TERMS Postmature - infant with recognizable clinical features indicating a pathologically prolonged pregnancy Postdates- should be abandoned, because the real issue in many postterm pregnancies is "post-what dates?“ Postterm or Prolonged Pregnancy - preferred expression for an extended pregnancy “Postmature" is reserved for a specific clinical fetal syndrome According to ACOG(1997) : 42 completed weeks (294 days) or more from the first day of the last menstrual period

  40. Postmaturity Syndrome Characteristic appearance / Features: wrinkled, patchy, peeling skin; a long, thin body suggesting wasting; and advanced maturity because the infant is open-eyed, unusually alert, and appears old and worried-looking Skin wrinkling prominent on the palms and soles Nails are long

  41. FETAL DISTRESS IN POSTTERM PREGNANCY antepartum fetal jeopardy and intrapartum fetal distress were the consequence of cord compression associated with oligohydramnios one or more prolonged decelerations preceded three fourths of emergency cesarean deliveries for fetal jeopardy findings are consistent with cord occlusion as the proximate cause of fetal distress other correlates found were oligohydramnios and viscous meconium


  43. Prolonged fetal heart rate deceleration prior to emergency cesarean delivery in a postterm pregnancy with oligohydramnios

  44. FETAL GROWTH RESTRICTION IN POSTTERM PREGNANCY stillbirths were more common among growth-restricted infants who were delivered at 42 weeks or beyond one third of the postterm stillbirths were growth restricted morbidity and mortality were significantly increased in the growth-restricted infants

  45. MANAGEMENT OF POSTTERM PREGNANCY Antepartum interventions are indicated in cases of postterm pregnancies When to induce? 41 or 42 weeks? 41 weeks with favorable cervix, induce lab or 41 weeks with unfavorable cervix, antepartum fetal testing 42 weeks, whether the cervix is favorable or not, labor is generally induced

  46. UNFAVORABLE CERVIX A cervix that is closed, uneffaced with a bishop score of less than 7 women in whom there was no cervical dilatation at 42 weeks had a twofold increased cesarean delivery rate for "dystocia“ cervical length of 3 cm or less determined by transvaginal ultrasonography was predictive of successful induction

  47. The American College of Obstetricians and Gynecologists (1997) has concluded that prostaglandin gel can be used safely in postterm pregnancies Sweeping or stripping of the membranes: decreased the frequency of postterm pregnancy. stripping did not modify the risk for cesarean delivery and maternal and neonatal infections were not increased Station of the vertex is important in predicting successful postterm induction. UNFAVORABLE CERVIX

  48. THANK YOU !