Postdated pregnancy for undergraduates

1. POST TERM
PREGNANCY

2. 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

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

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

5. 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.

6. Determining Gestational Age
 Naegele's rule
 Quickening (around 16 to 20 weeks GA)
 Uterine size, increases with GA
 Ultrasound examination in the first trimester
provides the most accurate dating
 Electronic Doppler ultrasound may detect
fetal heart tones as early as 10-11 weeks‘ GA

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

8. 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.

9. 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.

10. Etiology
 Wrong dates; inaccurate LMP (most common)
 Biological variability (hereditary/familial)
 Maternal factors: Primiparity, previous
prolonged pregnancy, sedentary habit and
obesity, elderly multiparae

11. Cont…
 Fetal factors: Congenital anomalies:
Anencephaly → abnormal fetal HPA axis and
adrenal hypoplasia → diminished fetal cortisol
response
 Placental factors: Sulphatase deficiency →
low estrogen
 Male baby

12. 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

13. Diagnosis
1. Menstrual history; useful if the patient is
sure about her date
2. Clinical findings;
 Weight record: Regular periodic weight
checking reveals stationary or even falling
weight
 Girth of the abdomen: It diminishes gradually
because of diminishing liquor
 History of false pain: that subsided

14. Cont…
 Obstetric palpation: The following findings,
taken together are helpful: height of the uterus,
size of the fetus and hardness of the skull
bones. As the liquor amnii diminishes, the
uterus feels “full of fetus” a feature usually
ass/c post-maturity
 Internal examination: While a ripe cervix is
usually suggestive of fetal maturity, to find an
unripe cervix does not exclude maturity.
Feeling of hard skull bones either through the
cervix or through the fornix usually suggests
maturity

15. Investigations
Aims are:
 To confirm the fetal maturity
 To detect placental insufficiency (fetal well
being)

16. Cont…
1. To confirm fetal maturity
 Sonography; Early ultrasound scan (in the 1st
trimester) can reduce the incidence of true
post-maturity
 Amniocentesis: The biochemical and
cytological parameters are helpful. However,
this invasive method has been mostly replaced
by sonography

17. Cont…
 Straight X-ray abdomen: Thickness and
density of the skull bone shadow, appearance
and density of the ossification centers in the
upper end of the tibia (38–40 weeks) and
lower end of the femur (36–37 weeks) are
taken together to assess the maturity
 Not commonly done

18. Cont…
2. Fetal well being assessment; done by twice
weekly,
 Nonstress test
 Biophysical profile (heart rate, movement,
breathing, and amnionic fluid volume)

19. 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.

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

21. 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

22. 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)

23.  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)

24.  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

25. Symptoms of post-maturity in a
newborn
 Dry loose peeling skin
 Large amount of hair on the head
 Overgrown nails
 Green-yellowish/brownish coloring of the skin
from in-uteral passing of meconium
 More alert and wide-eyed

26. Induction versus expectant management:
 compared with delivery induction, expectant
management associated with
 decreased mortality risk at 37 weeks gestation (relative risk
[RR] 0.87. 95% CI 0.77-0.99)
 similar mortality risk at 38 weeks gestation (RR 1.11, 95% CI
1-1.22)
 increased mortality risk at
 39 weeks gestation (RR 1.47, 95% CI 1.35-1.59)
 40 weeks gestation (RR 1.58, 95% CI 1.45-1.71)
 41 weeks gestation (RR 1.63, 95% CI 1.47-1.81)
Reference - Obstet Gynecol 2012 Jul;120(1):76

27. 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.