POST TERM PREGNANCY

Definitions:  postdates pregnancy - patient who has not delivered by end of 42nd week or 294 days from first day of last menstrual period (LMP)  prolonged pregnancy - exceeds 40 weeks (280 days) from known time of ovulation

Incidence:  27 percent of pregnancies deliver in the 40 th and 41 st week.  5.5 percent deliver at ≥42 weeks.

Incidence:  pregnancies dated by first trimester ultrasound examination:  ≥41 weeks ranges from 5 to 11 percent  ≥42 weeks is about 2 percent

Causes:  The commonest cause is error in calculation of gestational age.  Congenital anomalies like anencephaly which disrupt foetal pitutary adrenal axis and rare maternal enzyme deficiencie(placental sulphatase.  In most cases cause is not known.

Risk Factors  Maternal or paternal personal history of postterm birth  Nulliparity  Male fetus  Maternal obesity  Older maternal age  lower socioeconomic groups

Pathogenesis:  amniotic fluid volume decreases  amniotic fluid volume reaches maximum at 24 weeks, constant until 37 weeks, then decreases  decreased amniotic fluid volume associated with decreased fetal movement and fetal heart rate decelerations

A. Fetal Complications  Still birth rate increases significantly at term with advancing gestation. It is 0.35/1000 pregnancies at 37 weeks While 2.12/1000 pregnancies at 43 weeks.

Meconium aspiration Macrosomia Asphyxia before, during and after delivery Fractures and Peripheral nerve injury Pneumonia Septicaemia Intra cranial hemorrhage

Dysmaturity (postmaturity syndrome)  Incidence 20%  stage 1 - alert facial expression; recent weight loss with decreased subcutaneous fat and muscle mass  stage 2 - green meconium staining of skin and umbilicus, fetal distress, hypoxia  stage 3 - yellow staining of nails, skin and umbilicus indicative of prolonged passage of meconium

B. Maternal Complications  cesarean delivery  rates of primary cesarean delivery 8.2% at 38 weeks 8.8% at 39 weeks 9% at 40 weeks 14% at 41 weeks (p < 0.001) 21.7% at ≥ 42 weeks (p < 0.001)

 operative vaginal delivery 8.8% at 38 weeks 9.4% at 39 weeks 10.9% at 40 weeks (p < 0.001) 13.3% at 41 weeks (p < 0.001) 17.4% at ≥ 42 weeks (p < 0.001)

postpartum hemorrhage, starting at 38 weeks third- or fourth-degree laceration, starting at 39 weeks prolonged labor (> 24 hours), starting at 39 weeks chorioamnionitis, starting at 40 weeks endomyometritis, starting at 41 weeks

Induction versus expectant management:  compared with delivery induction, expectant management associated with decreased mortality risk at 37 weeks gestation (relative risk [RR] % CI ) similar mortality risk at 38 weeks gestation (RR 1.11, 95% CI ) increased mortality risk at 39 weeks gestation (RR 1.47, 95% CI ) 40 weeks gestation (RR 1.58, 95% CI ) 41 weeks gestation (RR 1.63, 95% CI ) Reference - Obstet Gynecol 2012 Jul;120(1):76Obstet Gynecol 2012 Jul;120(1):76

Prevention:  Recording LMP and calculating EDD at the time of first ANC visit.  Routine early ultrasound for dating of pregnancy.  Review of antenatal card and ultra sonographic reports in terms of fetal growth.  Sweeping of membranes from 38 wks onwards decreases number of pregnancies going beyond 41 and 42 wks.  As soon as prematurity is ruled out in high risk cases induction of labour will prevent post maturity.