Prolonged Preg

武功密笈

小黃藏書

Prolonged Preg

~ Managing Prolonged Pregnancy ~

§ Errors in determining the time of ovulation and conception are the most frequent

cause of what appears to be prolonged gestation.

§ Definition of postterm pregnancy: (Definition by WHO and FIGO)

– 42 completed weeks or more

　

§ Useful measurement for dating pregnancy by ultrasound:

– Fetal crown-rump length (CRL) during the first trimester

– Biparietal diameter (BPD) or head circumference and femur length (FL) during

the second trimester

ø Dating the pregnancy in the third trimester is unreliable because of normal variations in the

size of infants at that time (± 3 weeks)

　

§ Conditions associated with prolonged pregnancy:

? Primigravidae

‚ Previous prolonged gestations.

　

§ Conditions associated with adverse perinatal outcome in postterm pregnancy:

? Hypertension or preeclampsia

‚ Diabetes

ƒ Abruptio placentae

„ Intrauterine growth restriction

　

§ Possible complications of prolonged pregnancy:

? Meconium staining of the amniotic fluid

‚ Macrosomia, with associated dystocia and brachial plexus injury

ƒ Intrapartum fetal hypoxia, which may result in fetal acidosis, neonatal

seizures, and intrapartum stillbirth or neonatal death

ø Perinatal death is lowest at 40 weeks’ gestation (2.3/1000), with an increase to 3.0/1000 at 42

weeks and 4.0/1000 at 43 weeks.

　

§ Approach to prolonged pregnancy:

< 20 weeks’ gestational age

Establish gestational age by certain LMP or dating ultrasound

At 39-40 weeks, discuss options with patient

for management at 41 weeks

For patients with risk factors, elective induction

is preferred.

For patient without risk factors, expectant

management or elective induction both

acceptable. The latter may further decrease

the risk of perinatal mortality, and will not

increase the likelihood of having a C/S.

　

　

At 41 weeks

Patients with risk factors Patients without risk factors

Bleeding

Increased blood pressure

Intrauterine growth restriction Elective induction Serial fetal surveillance

Macrosomia Fetal kick counts

Diabetes mellitus NST

Hydramnios AFI

Multiple pregnancy Biophysical profile

Elective induction Abnormal findings Spontaneous labor

Selective induction

? Elective/Selective induction:

For unripe cervix:

Ò Prostaglandins or mechanical methods ± oxytocin

For ripe cervix:

¬ If presenting part low

Ò amniotomy ± oxytocin

¬ If presenting part high

Ò Prostaglandins or controlled amniotomy ± oxytocin

　

§ References:

1. Managing prolonged pregnancy. Victoria M. Allen, MSc, MD, FRCSC, and Mary E. Hannah,

MD/CM, FRCSC. Contemporary OB/GYN April 2000

Filename: Managing Prolonged Pregnancy

word.doc