Post Term Pregnancy

The student at the end of this lecture should be able to : Diagnose post term pregnancy in suspected case. Determine the consequences of prolongation of pregnancy beyond the expected date. Planning delivery in a post term pregnancy depending on fetal well being and bishop score. Describe labor in postterm pregnancy

Post term pregnancy: Post term pregnancy (prolonged): is that pregnancy persist beyond 42 weeks (294 days) from the onset of last menstrual period. Incidence : 6 – 12 % of all pregnancies .

The risks of post term pregnancy : Are because of Postmaturity(dysmaturity) syndrome : Occuring in 20-30% of post term pregnancies related to aging and infarction of the placenta result into placental insufficiency. Intrauterine hypoxia may be manifested as meconium staining. Fetus with postmaturity syndrome may have loss of subcutaneous fat ,long finger nails ,dry peeling skin and abundant hair.

Other wise the fetus grow in uterus to a point of macrosomia ; may results in abnormal labor ,shoulder dystocia , birth trauma and increased incidence of caesarean section .

Etiology : Initiation of human labour is by complex maternal and fetal factors .The cause of postdate pregnancy is unknown in most instances and occurs in healthy pregnancy. Rare association is with : Anencephalic pregnancy (hypoplastic Adrenal gland), placental sulfatase deficiency and extrauterine pregnancy.

Diagnosis: The diagnosis is difficult . Accurate dating of gestation is the key for diagnosis and perinatal management . There are factors to be evaluated in dating a pregnancy to determine whether it’s a misdated or postdated pregnancy .

Factors evaluated in dating pregnancy Accurate date of Lmp. Uterus size by (bimanual Pelvic examination 1st trimester( Uterus size/date discrepancy during antenatal care. Gestational age when the fetal heart tones first heard (doppler ultrasound at 12-14 weeks). Gestational age when the fetal heart first heard (DeLee stethoscope 18-20 weeks). Date of quickening(18-20 w in primi 16-18 in multi) Sonographic parameters (bipariatal diameter between 16-20 weeks) If there is no concordance between 2 factors this mean the patient have poor date .

Management of post term pregnancy Antepartum management ; Decision of delivery : If the patient is <42 weeks with engaged head and favorable cervix then labour should be induced . Patient with <42 week and unfavorable cervix: Twice weekly NST and BPP. AFI amniotic fluid index (sum of 4 pocket of liquor in 4 quadrant).

-until the cervix is favorable . If the result is reassuring then follow up and delivery is indicated : -until the cervix is favorable . -result is abnormal (deceleration, AFI is oligohydramnia <=5) . -Fetal macrosomia . -43 weeks regardless of other factors because of increased perinatal morbidity and mortality .

Patient present late in gestation with the label of prolonged pregnancy in question, expectant approach is acceptable and risk of intervention with delivery of preterm infant must be considered .

Intrapartum management : Continuous electronic fetal monitoring during induction of labour. Membranes should be ruptured early in labour to assess the color of amniotic fluid and to apply internal electrodes. If there is fetal distress (fetal blood sampling) then C.S. is indicated .