Preterm birth PTB

1. Preterm birth (PTB A birth that occurs before 37 completed weeks of gestation. Subclassifications of PTB are variably and inconsistently defined as: Late preterm = 34 to 36 weeks Moderately preterm = 32 to 34 weeks Very preterm = <32 weeks Extremely preterm = <28 weeks PTB can also be defined by birth weight (BW): Low birth weight (LBW) � BW less than 2500 g Very low birth weight (VLBW) � BW less than 1500 g Extremely low birth weight (ELBW) � BW less than 1000 g

2. SIGNIFICANCE� Taken together with its sequelae, PTB is by far the leading cause of infant mortality in the United States. PTB is also a major determinant of short- and long-term morbidity in infants and children. INCIDENCE���In the United States, 12.8 percent of births in 2006 occurred preterm and 3.66 percent were less than 34 weeks of gestation

3. PATHOGENESIS� Approximately 70 to 80 percent of PTBs occur spontaneously. preterm labor (PTL) accounts for 40 to 50 percent of all PTBs and preterm premature rupture of membranes (PPROM) accounts for 20 to 30 percent. The remaining 20 to 30 percent of PTBs are due to intervention for maternal or fetal problems

4. Clinical and laboratory evidence suggest that a number of pathogenic processes can lead to a final common pathway that results in preterm labor and delivery. The four primary processes are: Activation of the maternal or fetal hypothalamic-pituitary-adrenal axis Infection Decidual hemorrhage Pathological uterine distention

5. RISK FA CLINICAL MANIFESTATIONS AND DIAGNOSIS FACTORS �PTL is one of the most common reasons for hospitalization of pregnant women. In one systematic review, approximately 30 percent of preterm labors spontaneously resolved. Signs and symptoms of early PTL include menstrual-like cramping, constant low back ache, mild uterine contractions at infrequent and/or irregular intervals, and bloody show. However, these signs and symptoms are non-specific and often noted in women whose pregnancies go to term.

6. Uterine contractions are a normal finding at all stages of pregnancy, thereby adding to the challenge of distinguishing true from false labor. The frequency of contractions increases with gestational age, the number of fetuses, and at night. The diagnosis of PTL is generally based upon clinical criteria of regular painful uterine contractions accompanied by cervical dilation and/or effacement. Specific criteria, which were initially developed to select subjects in research settings, include persistent uterine contractions (four every 20 minutes or eight every 60 minutes) with documented cervical change or cervical effacement of at least 80 percent, or cervical dilatation greater than 2 cm. Digital cervical examination has limited reproducibility between examiners, especially when changes are not pronounced; therefore, some centers evaluate the cervix via transvaginal ultrasound to confirm the diagnosis A short cervix has been variously defined as a cervical length less than 2.0 cm, 2.5 cm, or 3.0 cm.

7. initial evaluation of women with suspected PTL should determine: The The presence and frequency of uterine contractions Whether there is uterine bleeding Whether the fetal membranes have ruptured Gestational age Fetal well-being

8. Physical examination� The uterus is examined to assess firmness, tenderness, fetal size, and fetal position. A sterile speculum examination is performed to rule out ruptured membranes, to visually examine the vagina and cervix, Obtain specimens for laboratory testing . A digital examination to assess cervical dilatation and effacement is performed after placenta previa and PPROM have been excluded

9. Laboratory tests Urine culture, since bacteriuria and pyelonephritis are associated with PTB. Rectovaginal group B streptococcal culture, to determine need for antibiotic prophylaxis. Tests for gonorrhea and chlamydia. Testing for gonorrhea and chlamydia may be omitted if previously performed, the results were negative, and the patient is not at high risk of acquiring sexually transmitted infections. Fetal fibronectin (fFN),a swab for fFN on all symptomatic patients considered at high risk for PTB. Perform transvaginal sonographic measurement of cervical length. We only send the swab to the laboratory for FFN determination if the cervical length is 20 to 30 mm Given the link between cocaine use and placental abruption, perform drug testing in patients with risk factors for drug abuse.

10. TRIAGE BASED UPON CERVICAL LENGTH Cervical length >30 mm���These women are at low�risk of PTB, Regardless of fFN result. Discharge the patients home after an observational period of four to six hours during which confirm fetal well-being Exclude the presence of an acute precipitating event (eg, an abruption or overt infection), Follow-up in one to two weeks Cervical length 20 to 30 mm���PTB is more likely in women with cervices 20 to 30 mm than in women with longer cervices, but most women in this group do not deliver preterm. Therefore, send the swab for fFN testing in this subgroup of women. If the test is positive (level greater than 50 ng/mL), then actively manage the pregnancy to prevent morbidity associated with PTB. Cervical length <20 mm�.These women are at high�risk of PTB regardless of fFN result. Therefore, we do not send their swabs for fFN testing to the laboratory and actively manage them to prevent morbidity associated with PTB.

11. MANAGEMENT OF WOMEN WITH PRETERM LABOR Hospitalize women diagnosed with PTL at less than 34 weeks of gestation and initiate the following treatments: Antenatal glucocorticoids to reduce neonatal morbidity and mortality associated with PTB Appropriate antibiotics for GBS chemoprophylaxis Tocolytic drugs for up to 48 hours to delay delivery so that glucocorticoids given to the mother can achieve their maximum effect. Appropriate antibiotics to women with positive urine culture results or positive tests for gonorrhea or chlamydia.

12. MANAGEMENT OF ASYMPTOMATIC WOMEN AT HIGH RISK OF PTB�� �Interventions to prevent PTB generally have not been successful, with some exceptions (eg, supplemental progesterone). Women with risk factors for PTB are sometimes followed with serial ultrasound measurement of cervical length. A cervical length =35 mm is generally considered normal and reassuring; as cervical length decreases below 35 mm, the risk of PTB increases We manage asymptomatic patients at high risk of PTB similar to the way we manage symptomatic patients, but with a higher cervical length threshold for intervention. This minimizes overtreatment of high risk asymptomatic patients and undertreatment of symptomatic patients. Surveillance with serial cervical length measurements is begun at 22 weeks. Cervical length =35 mm - The risk of PTB is low. See these patients in routine follow-up in one to two weeks. Cervical length 25 to 34 mm - obtain a fFN concentration. If the test is positive (level greater than 50 ng/mL), then actively manage the pregnancy to prevent morbidity associated with PTB. Cervical length <25 mm - The risk of PTB is increased. We actively manage the pregnancy to prevent morbidity associated with PTB, as described above.

13. Premature rupture of membranes (PROM Refers to membrane rupture before the onset of uterine contractions; preterm PROM (PPROM) is the term used when the pregnancy is less than 37 completed weeks of gestation. PPROM occurs in 3 percent of pregnancies and is responsible for, or associated with, approximately one-third of preterm births. In management of PPROM, Points of contention include: Expectant management versus intervention Use of tocolytics Duration of administration of antibiotic prophylaxis Timing of administration of antenatal glucocorticoids Methods of testing for maternal/fetal infection Timing of delivery.

14. ETIOLOGY AND RISK FACTORS �The pathogenesis of PPROM is not completely understood. There are multiple etiologies, mechanical and physiological, that probably share a final common pathway leading to membrane rupture. Risk factors for PPROM are similar to those for preterm labor A history of PPROM in a previous pregnancy Genital tract infection Antepartum bleeding Cigarette smoking have a particularly strong association with PPROM Although a small randomized trial suggested vitamin C�supplementation might lower the risk of PPROM , a larger randomized trial in which both vitamin C and E were given refuted this finding and suggested the risk of PPROM may actually be increased with antioxidant supplementation .

15. OUTCOME �Approximately one-third of women with PPROM develop potentially serious infections, such as intraamniotic infection (chorioamnionitis), endometritis, or septicemia. Endometritis is more common after cesarean than vaginal delivery. The fetus and neonate are at greater risk of PPROM-related morbidity and mortality than the mother. The majority of pregnancies with PPROM deliver preterm and within one week of membrane rupture.

16. OUTCOME Preterm infants are especially vulnerable to a variety of problems, such as hyaline membrane disease, intraventricular hemorrhage, periventricular leukomalacia and other neurologic sequelae, infection (eg, sepsis, pneumonia, meningitis), and necrotizing enterocolitis. The rates of these morbidities vary with gestational age and are higher in the setting of chorioamnionitis PPROM is also associated with increased risks of abruptio placentae and prolapse of the umbilical cord. Fetal malpresentation is common, given the preterm gestational age and the frequent occurrence of reduced amniotic fluid volume. The risk of cord prolapse is especially high (11 percent in one study) in the setting of both nonvertex fetal presentation and PPROM. Early, severe, prolonged oligohydramnios can be associated with pulmonary hypoplasia, facial deformation, and orthopedic abnormalities. Such complications are most likely when membrane rupture occurs at less than 23 weeks of gestation.

17. Risk factors for preterm birth Stress Single womenLow socioeconomic statusAnxietyDepressionLife events (divorce, separation, death)Abdominal surgery during pregnancy Occupational fatigue Upright postureUse of industrial machinesPhysical exertionMental or environmental stress Excessive or impaired uterine distention Multiple gestationPolyhydramniosUterine anomalyUterine leiomyomaDiethylstilbestrol Cervical factors History of second trimester abortionHistory of cervical surgeryPremature cervical dilatation or effacement Infection Sexually transmitted infectionsPyelonephritis, appendicitis, pneumoniaSystemic infectionBacteriuriaPeriodontal disease Placental pathology Placenta previaAbruptionVaginal bleeding Miscellaneous Previous preterm deliverySubstance abuseSmokingMaternal age (<18 or >40)African-American racePoor nutrition and low body mass indexInadequate prenatal careAnemia (hemoglobin <10 g/dL)Excessive uterine contractilityLow level of educational achievementGenotype Fetal factors Congenital anomalyGrowth restriction

18. CLINICAL MANIFESTATIONS AND DIAGNOSIS History���The classic clinical presentation of PPROM is a sudden "gush" of clear or pale yellow fluid from the vagina. However, many women describe intermittent or constant leaking of small amounts of fluid or just a sensation of wetness within the vagina or on the perineum. A clinical history suggestive of PPROM should be confirmed by visual inspection or laboratory tests to exclude other causes of vaginal/perineal wetness, such as urinary incontinence, vaginal discharge, and perspiration. Physical examination���The best method of confirming the diagnosis of PPROM is direct observation of amniotic fluid coming out of the cervical canal or pooling in the vaginal fornix. If amniotic fluid is not immediately visible, the woman can be asked to push on her fundus, Valsalva, or cough to provoke leakage of amniotic fluid from the cervical os. Digital examination should be avoided because it may decrease the latency period (ie, time from rupture of membranes to delivery) and increase the risk of intrauterine infection Nitrazine and fern tests���If PROM is not obvious after visual inspection, the diagnosis can be confirmed by testing the pH of the vaginal fluid, which is easily accomplished with nitrazine paper. Amniotic fluid usually has a pH range of 7.0 to 7.3 compared to the normally acidic vaginal pH of 3.8 to 4.2

19. False-negative and false-positive nitrazine tests results occur in up to 5 percent of cases. False negative tests results can occur when leaking is intermittent or the amniotic fluid is diluted by other vaginal fluids. False positive results can be due to the presence of alkaline fluids in the vagina, such as blood, seminal fluid, or soap. In addition, the pH of urine can be elevated to near 8.0 if infected with Proteus species. In the United Kingdom, an absorbent pad (AmnioSense) that changes color at pH > 5.2 is used as a panty liner and marketed to pregnant women. In a study of 157 pregnant women, the sensitivity and specificity of this device for diagnosis of membrane rupture were 98 and 65 percent, respectively Ultrasonography���Ultrasound examination may be of value in the diagnosis of PPROM. Fifty to 70 percent of women with PPROM have low amniotic fluid volume on initial sonography . A mild reduction of amniotic fluid volume may have many etiologies. On the other hand, the finding of anhydramnios or severe oligohydramnios, combined with a characteristic history, is highly suggestive of rupture of membranes, although renal agenesis, obstructive uropathy, or severe utero-placental insufficiency also can cause marked reductions in amniotic fluid volume. Instillation of indigo carmine��One-half hour later, the tampon is removed and examined for blue staining, which indicates leakage of amniotic fluid.

20. The management of pregnancies complicated by PPROM is based upon consideration of several factors, which are assessed upon presentation: Gestational age Availability of neonatal intensive care Presence or absence of maternal/fetal infection Presence or absence of labor Fetal presentation (Breech and transverse lies are unstable and may increase the risk for cord prolapse) Fetal heart rate (FHR) tracing pattern Likelihood of fetal lung maturity Cervical status (by visual, not digital, inspection unless induction is planned or the woman is in labor)

21. Initial evaluation� Expeditious delivery of women with PPROM is indicated if intrauterine infection, abruptio placentae, repetitive FHR decelerations, or a high risk of cord prolapse is present or suspected In each of these conditions, fetal well-being can deteriorate with expectant management, and there are no therapeutic interventions available other than delivery.

22. Our simplified algorithm for management of other women with PPROM is shown in the Antenatal glucocorticoids� Antibiotics Treatment of overt infections� Tocolysis Hospitalization Tissue sealants (A variety of tissue sealants (eg, fibrin glue, gelatin sponge) have shown some success in stopping leakage in case reports. Neither the safety nor the efficacy of these sealants has been established ). Supplemental progesterone (There is no evidence that administration of supplemental progesterone�has any beneficial effects in women with PPROM )

23. Maternal surveillance� Fetal surveillance �Timing of delivery Gestational age <34 weeks���In general, prematurity is the greatest risk to the fetus with PPROM As discussed above, we administer a course of antenatal glucocorticoids, prophylactic antibiotics for seven days, and tocolytics for 48 hours, as indicated. Gestational age greater than 34 weeks� Method of delivery���Cesarean delivery is performed for standard indications; otherwise labor is induced. Favorable Cervix vs Unfavorable cervix�