Dr.Amina Zakaria Al-tutunji
M.B.Ch.B, MD.Obstetrics and Gynecology
College of medicine/University of Mosul
Post term pregnancy (prolonged pregnancy)
Definition
Post term: pregnancy that extends beyond 42 wks (>294 ds) from the first day of LMP
Post date: pregnancy that extends beyond 40 wks (>280 ds)
Incidence of post-term pregnancy is 4-14%.
Etiology
1-unknown
2-inaccurate dating (pt doesn't remember the LMP)
3-biological variability (hormonal factors & genetic predisposition)
4-maternal factors (previous prolonged pregnancy, primi-parity, irrigular MC, obesity, elderly multipara)
5-fetal factors; congenital anomalies (anencephaly)
6-placental factors; sulfatase deficiency
7-extrauterine pregnancy (v. rare)
Pathophysiology
Abnormal fetal hypothalamic-pitutary-adrenal & adrenal hypoplasia as in anencephaly, deficiency of dehydro-epiandrosterone reduced fetal cortisol response.Placental sulphatase deficiency , this enzyme play a critical role in synthesis of placental estrogens which is necessary for expression of oxytocin & PG receptors in myometerial cells.
Physiological changes associated with post-term pregnancy
*Placental changes: ageing of the placenta, calcification, infarctions
*Amniotic fluid changes: oligohydromnios, cloudy ( flakes of vernix), presence of meconium
*Fetal changes: 45% macrosomia, intra-uterine malformation.
Diagnosis
1-History: calculation of GA, LMP, lactational amenorrhoea, uses of CCP
2-Examination; larger baby size
3-Investigation,
-Non-invasive methods as;
a-radiography: ossification centers upper & lower ends of tibia, femur, thickness & density of skull bone shadow
b-non stress criteria: records fetus movement, heart beat & contractions
c- USG: increased HC, AC & BPD, oligohydromnois, increased placental calcification
d-biophysical test (amniotic fluid index)
e-doppler flow study: amount of blood flowing in & out of placenta
4-Invasive methods as amniocentesis; orange colour cells, presence of phophatidyl glycerol, creatinine concentration
Fig.1 Biophysical profile score
Complications (Risks)Maternal
-Increased morbidity due to increased instrumental & operative delivery (CS)
-Psychological stress
-Increased risk of PPH
Fetal
-Intra-partum fetal distress
-Fetal hypoxia & acidosis may be manifested as meconium staning
-Meconium aspiration syndrome
-Fetal trauma due to macrosomia (brachial plexus injuries, clavicle fracture)
-Neonatal complications (hypoglycemia, pneumonia, septicaemia,,,)
-Increased perinatal morbidity & mortality
-Shoulder dystocia
-Oligohydromnioa
-Post-maturity syndrome (occuring in 20-30% of post term pregnancy , it related to ageing & infarction of placenta result to placental insufficiency)
Fig.2 Meconium aspiration
Management
Assessment of GA by;
-calculating the EDD based on first day of LMP
-first trimester CRL
-USG estimation of BPD between 16-20wks
-a record of bimanual examination in 1st trimester or fundal height in 2nd trimester
-doppler FH tone at 10 wks
-date of quickening (16-18wks in multi & 18-20wks in primi)
Intra-partum management
1-left lateral position
2-continuous electrical fetal monitoring
3-early ARM in active phase to assess the colour of amniotic fluid
4-amnio-infusion (750-1000 ml NS)
5-LSCS in case of CPD, macrosomia or fetal disterss
6-pediatrician called at delivery
7-Once pregnancy reaches 42 wks, delivery mandatory by induction or CS
Expectant management of prolonged pregnancy is justified only when;
1-GA< 41 wks with un-ripe cervix
2-normal AFI
3-normal size baby
4-normal BPP & NST
Patient with prolonged pregnancy (>40 wks) who need to be delivered;
1-women with medical or obstetrical complications during pregnancy
2-favorable cervix Bishop score >8
3-estimated fetal wt >4.5kg
4-woman with oligo-hydromnios
5-abnormal NST& BPP
6-fetal congenital anomaly
7-hyper-mature placenta
Characteristics of post-term baby
-decreased amount of soft tissue mass particularly subcutaneous fat, the skin may hang loosely on the extremities & is often dry & peeling. (Fig.3)
-the finger nails & toenails are long
-the nail & umbilical cord may be stained with meconium
-baby wt.> 4.5 kg
-skull is well ossified with smaller fontanelles
Prevention
-Recording LMP & calculating EDD at time of first ANC visit
-Routine early USG for dating of pregnancy Fig.3 Post term baby
-Sweeping of membranes from 38 wks onwards decreases the incidence of post-term pregnancy.
Fig.4 Chemical test performed on amniotic fluid