POSTTERM PREGNANCY AZZA ALYAMANI OBSTETRICS & GYNICOLOGY Department King Khalid University

Introduction Post term pregnancy is a common situation. It cause anxiety for both women and obstetricians because it perceived as being a cause of increased risk to the fetus. Post term pregnancy per se is not a pathological condition and should not be confused with the post maturity syndrome described by Clifford in 1954.

Definitions

* Post term ( prolonged pregnancy ) : it is 42 completed weeks or more ( 294 days). this definition is accepted by both WHO & FIGO. * Post maturity syndrome : it is IUGR with associations of ,meconium stained amniotic fluid , oligohydramnios , fetal distress , loss of subcutaneous fat and dry cracked skin reflecting placental insufficiency. * Past date : past the calculated EDD before 42 weeks.

Incidence : 5 -10 % Dating by the last menstrual period (LMP) alone , has a tendency to overestimate the GA . While the use of early ultrasound alone , to calculate GA , significantly reduced the incidence of post term pregnancy . Ia

Importance Fetal and Neonatal risks * It is likely that the majority of morbidity and mortality associated with post term pregnancy, arises because of post maturity. * Post term pregnancies are associated with excess perinatal morbidity & mortality . * Delivery at 42 week is associated with a doubling of the perinatal mortality rate , unlike the 37 -41 week period in which antepartum deaths contribute about 2/3 of the total .

When lethal congenital abnormalities are excluded ,intrapartum fetal death is 4 times more common, and neonatal death is 3 times more common in infant s born after 42 weeks.

In addition , meconium staining of the amniotic fluid and the likely of intrapartum fetal hypoxia were much more common in post term pregnancies compared to those delivered at 40 ws. This result in fetal acidosis , neonatal seizures & perinatal death . Post term pregnancy is also a risk factor for birth trauma and shoulder dystocia.

B) Maternal risks of post term pregnancies: * increased operative delivery , hemorrhage and maternal infection. * in addition , psychological morbidity as increased maternal anxiety .

Etiology Not Clear It is common in : * primigravida * previous post term pregnancy. 30% The cause may be due to : 1. low cortisol levels with post term fetal distress. 2. relative adrenocortical insufficiency leading to delay in the onset of labor & increased risk of intrapartum hypoxia or death.

Support for this theory is that : infants delivered following a post term pregnancies are at increased risk of : * sudden infant death syndrome. * death up to 2 years of age.

Fetal Assessment

Monitoring Post term Pregnancy The perinatal mortality does not significantly rise until 42 ws. gestation ,thus there is no need to offer fetal monitoring prior to this gestation, if it is not offered at term . There is no consensus about the appropriate surveillance to post term pregnancy and no clear evidence exists to support that fetal monitoring can reduce the perinatal mortality.

* simple fetal monitoring is as effective as more sophisticated monitoring of post term pregnancies * The use of Doppler analysis of various arterial systems as uterine , umbilical ,middle cerebral and descending aorta in uncomplicated post term pregnancies is not different from that in term pregnancies.

the recommended fetal monitoring Therefore the recommended fetal monitoring in post term pregnancy is

Liquor volume fall after term , thus AFI does a) Amniotic fluid measurement Liquor volume fall after term , thus AFI does not improve perinatal outcomes , thus the mean pool depth (MPD) is the tool of choice for monitoring liquor in post term pregnancy. Ib b) CTG Simple monitoring with NST and liquor assessment holds an advantage over the formal biophysical profile scoring.

It is therefore ,vital that each woman is treated on an individual basis and counseled regarding the risks of post term pregnancy.

Management

to reduce perinatal mortality , meconium staining (1) induction of labor at 41+ weeks to reduce perinatal mortality , meconium staining of the amniotic fluid and small decrease in caesarean section rate . 1a (2) conservative management with close fetal surveillance, this can reduce excess operative delivery in women who will opt to for conservative management .

Other interventions: a. nipple stimulation but have not been shown to be of benefit . b. sweeping the membranes at or beyond 40 weeks appear to significantly reduce the incidence of post term pregnancy and should be offered to all women.

1. the use of early ultrasound dating , reduces the Key points: 1. the use of early ultrasound dating , reduces the incidence of postterm pregnancy. 2. induction of labor after 41+ weeks reduces perinatal mortality rates without increasing CS rates. 3. sweeping the membranes significantly reduces the incidence of postterm pregnancy . 4. no clear evidence that fetal monitoring can reduce the perinatal mortality in postterm pregnancy. 5. the use of NST and liquor assessment in monitoring postterm pregnancy twice weekly is recommended in women who prefer conservative management with fetal surveillance.

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