Prolonged Pregnancy(Evidence Based) Dr. Sunil
DEFINITION Prolonged pregnancy ( postterm pregnancy ) It is one that has lasted longer than 42 weeks or 294 days beyond the first day of the last menstrual period ( WHO & FIGO )
DEFINITION • Postdatism is pregnancy lasting beyond the estimated due date at 40 weeks. • “Postmature” is reserved for the pathologic syndrome in which the fetus experiences placental insufficiency and resultant IUGR .
Post-maturity syndrome • Representing 20 % cases of prolonged pregnancy and is associated with : • Meconium -stained amniotic fluid, • Oligohydramnios • Fetal distress • Evidence of loss of subcutaneous fat and • Dry, cracked skin Reflecting placental insufficiency.
Etiologic Factors • The most frequent cause is an error in dating. • When truly exists, the cause usually is unknown. • Primiparity and prior postterm pregnancy are the most common identifiable risk factors.
Etiologic Factors • Rarely, it may be associated with placental sulfatase deficiency or fetal anencephaly. • Male sex also has been associated. • Genetic predisposition may play a role .
EPIDEMIOLOGY • Using the definition of 294 days, the incidence of postterm pregnancy is 9 - 10 %.
Risks to the Fetus • The perinatal mortality: > 42 weekstwice that at term > 43 weeks > 6-fold that at term
Risks to the Fetus • In some cases, the risks appear to be due to uteroplacental insufficiency, resulting in fetal hypoxia , meconium aspiration, growth restriction, and oligohydramnios . • Fetal distress and meconium release were twice as common (at or after 42 weeks) than at term. • There was an eight-fold increase in meconium aspiration
Macrosomia - In other cases, continued growth of the fetus leads tomacrosomia, increasing the risk of labor abnormalities, shoulder dystocia with resultant risks of orthopedic or neurologic injury. - Macrosomia is far more common in postterm than term pregnancies .
Oligohydramnios • It is a marker for fetal compromise and it puts the fetus at risk for cord accidents. • U/S diagnosis : • No vertical pocket > 2 cm or • Amniotic fluid index (AFI) 5 cm or less . • It is considered an indication for delivery.
Risks to the Fetus • Fetuses born postterm also are at increased risk of : Sudden infant death syndrome(death within the first year of life). • Some of these deaths clearly result from peripartum complications (such as meconium aspiration syndrome), but most have no known cause.
Maternal risks • Labor dystocia • Severe perineal injury related to macrosomia • Doubling in the rate of cesarean delivery. • A source of extreme anxiety for the pregnant woman.
Gestational age calculation • Gest. age must be assessed carefully to avoid delivery of a preterm infant. • Women who attend late for ANC may be of uncertain gestation and may be over-represented in populations of postterm pregnancies. • Dating by the last menstrual period (LMP) alone has a tendency to overestimate the gestational age.
Gestational age calculation • Because actual dates of conception are rarely known, theLMP is used as the reference point. • This can make the accuracy of gest. age determination unreliablebecause of : • Irregular menses . • Recent cessation of birth control pills. • Inconsistent ovulation times.
Routine early pregnancy ultrasound • Reduces the number of women who require induction of labour for apparent postterm pregnancy . • It is recommended that all pregnant ladies (and certainly those who do not have regular menses), should have an ultrasound examination for gestational age determination, prior to 20 weeks RCOG,COCHRANE
Ultrasound biometry margins of error • Crown-rump length (CRL) till 12 weeks is 3-5 days, • Biparietal diameter (BPD) at12-20 weeks is 1 week, • BPD at 20-30 weeks is 2 weeks, and • BPD after 30 weeks is 3 weeks. • If there is more than a one week discrepancy between the LMP and the ultrasound findings, the ultrasound data should be used to determine the EDD.
Transcerebellar diameter • When composite biometry is not consistent in all of the parameters (i.e. BPD, head circumference, abdominal circumference, femur length), using the transcerebellar diameter is a way to more accurately date a pregnancy • The diameter in millimeters corresponds to weeks of gestation up to 24 weeks.
The available evidences are strongly in support that dating by Early ultrasonography alone is the most accurate method for predicting EDD. RCOG (GRADE A)
Routine early pregnancy ultrasound • The use of early ultrasound alone to calculate the rate of postterm pregnancy in women who delivered spontaneously significantly reduced the postterm rate from 10 % to 1.5 %. RCOG (GRADE A)
Are there interventions that decrease the rate of postterm pregnancy? • Accurate dating on the basis of ultrasonography performed early in pregnancy . • Breast and nipple stimulation at term have not been shown to affect the incidence of postterm pregnancy. • Sweeping of the membranes at term : the data are still conflicting . ACOG Guidelines 2004
Management options depend on: • Gestational age, • Absence/presence of maternal risk factors and / or • Evidence of fetal compromise, and • Maternal preferences . • Successful management depends on effective counselling of women and their full involvement in the decision making process.
Historically, prolonged pregnancy has been managed in 2 ways , either : • Inducing labour at 41-42 weeks gestation or • Awaiting the onset of spontaneous labour, while monitoring the fetal wellbeing . • The decision is difficult and should not be taken lightly.
Routine induction of labour at 41 weeks • Although postterm pregnancy is defined as a pregnancy of 42 weeks or more of gestation, several large multicenter randomized studies reported favorable outcomes with routine induction as early as the beginning of 41 weeks of gestation. Cochrane 2006
Routine induction of labour at 41 weeks • A recent review in the Cochrane Library concluded that routine induction in low-risk pregnancies at or after 41 weeks' gestation is associated with : • A reduction in perinatal mortality, • No increase in the rate of instrumental or cesarean delivery. RCOG Grade A
Routine induction of labour at 41 weeks • Contrary to what many obstetricians believe, induction of labor for prolonged pregnancy does not increase the rate of cesarean section, rather, it decreases it. • The risk of fetal distress from uteroplacental insufficiency due to prolonged pregnancy can be reduced by induction of labor, even to the point of preventing perinatal death from asphyxia.
ANTEPARTUM FETAL SURVEILLANCE • There is insufficient evidence to indicate whether routine antenatal surveillance of low-risk patients between 40 and 42 weeks of gestation improves perinatal outcome but it is often performed during this period.
ANTEPARTUM FETAL SURVEILLANCE • The condition of the fetus can change quickly and thus, monitoring should be at frequent intervals, and that none of the tests are immune from false positives, false negatives • Boehm et al, demonstrated that twice-weekly testing of patients at risk for fetal distress was superior to weekly testing.
FETAL SURVEILLANCE A modified biophysical profile consisting of a: • non stress test and an • amniotic fluid index have been shown to be as sensitive as a full biophysical profile. RCOG Grade A
Induction of labour or expectant management? • Favorable cervix : Labor generally is induced because the risk of failed induction and subsequent cesarean delivery is low. • Unfavorable cervix :a small advantage to labor induction using cervical ripening agents (prostaglandins), when indicated, regardless of parity or method of induction. ACOG 2004 (Level C)
Management from 40-41 weeks gestation • A .Healthy, uncomplicated pregnancy and fetal growth/ amniotic fluid normal: • No evidence to support elective induction of labour • No evidence to support use of serial antenatal monitoring : non stress test (NST) or amniotic fluid index (AFI) .
Management at 40 - 41 weeks gestation • B. Presence of maternal risk factors or evidence of fetal compromise : • Recommend cervical ripening as necessary and induction of labour
Management at 41 weeks gestation • A. Healthy, uncomplicated pregnancy • Inform the woman of the options and risks/ benefits of labour induction versus expectant management, and offer her labour induction. • Establish the cervical (Bishop) Score and ensure a ripening agent (prostaglandin) prior to induction.
Management at 41 weeks gestation • B. If mother declines induction , then provide expectant management: • Daily fetal movement counts • Non stress test (NST) and Amniotic fluid index (AFI) twice/ week to 42 weeks. • If the NST or AFI is abnormal , then initiate induction immediately Induce at 42 weeks even if NST and AFI are normal.
Management during labour and delivery • Consider amniotomy to diagnose thick meconium. • If meconium is present then consider risk of meconium aspiration , continuous fetal assessment with electronic fetal monitoring (EFM) is recommended. • Be prepared for shoulder dystocia and neonatal resuscitation at delivery.
Key Clinical Recommendations • Labour induction at 41 weeks gestationis recommended over expectant management in women with postterm pregnancy to reduce the rate of cesarean delivery & perinatal mortality . (RCOG Grade A)
Key Clinical Recommendations • If Expectant management (41- 42 weeks) is chosen, the fetus should be monitored with twice weekly non-stress test , amniotic fluid index . - However, evidence of benefit is lacking. (RCOG Grade C )
Key Clinical Recommendations • Prostaglandin can be used in postterm pregnancies to promote cervical ripening and induce labor. • Delivery should be effected if there is evidence of : • fetal compromise or • oligohydramnios. ACOG 2004 (Level A)