Preterm Labour
Definition
It is the onset of labour before completed 37 weeks of pregnancy.
Incidence: 5-10%.
Aetiology
(I) Maternal causes:
1. Medical disorders:
– Preeclampsia. – Chronic nephritis. – Anaemia and malnutrition.
2. Antepartum haemorrhage:
– Placenta praevia, – Abruptio placentae.
3. Uterine anomalies:
– Septate uterus. – Incompetent cervix. – Fibroid uterus.
4. Psychological or hormonal.
(II) Foetal causes:
1- Congenital anomalies.
2- Intrauterine foetal death.
3- Polyhydramnios.
4- Multiple pregnancy.
5- Rh- isoimmunization.
6- Premature rupture of membranes.
(III) Idiopathic.
Risk of Prematurity:
(1) Birth trauma: particularly intracranial haemorrhage which is aggravated by hypoprothrombinaemia and capillary fragility present in premature.
(2) Respiratory distress syndrome (RDS): occurs due to deficient pulmonary surfactant which helps distension of the alveoli. A structureless hyaline membrane will develop within the alveolar ducts and atelectasis of the alveoli occurs. Dyspnoea and cyanosis develops 1-2 hours after delivery and death occurs after about 30 hours.
RDS is seen also in infants;
– to diabetic mothers,
– delivered by cesarean sections, or
– had intrapartum asphyxia.
(3) Hypothermia as a result of:
i) Decreased heat production due to;
– reduced muscle activity and – hypoglycemia.
ii) Increased heat loss due to;
– large surface area relative to body weight,
– lack of insulating fat,
– immaturity of the heat-regulating center.
(4) Infection especially respiratory due to:
i) immaturity of the immune mechanism,
ii) susceptibility of the delicate tissues to trauma.
(5) Hematological disorders:
i) Anemia due to :
– impaired hemopoiesis,
– increased RBCs destruction,
– poor iron stores in the liver which are filled in the last weeks of pregnancy.
ii) Hypoprothrombinaemia: due to liver immaturity this is in addition to capillary fragility increase the liability for hemorrhage.
iii) Hyperbilirubinaemia due to:
– liver immaturity and – increased RBCs destruction.
(6) Malnourishment due to:
– weak suckling, – weak digestion and – liver immaturity.
Rickets and impaired mental development occurs more frequently in premature children.
Post-term Pregnancy
Definition
A pregnancy that persists for 42 weeks or more from the onset of the last menstrual period. Sometimes called postmaturity or postdate.
Incidence: 5-10%. It is more common in primigravidae.
Aetiology
Unknown, but hereditary, hormonal and non-engagement of the presenting part are suspected factors.
Risk of Post-term
1. Placental insufficiency: This may lead to fetal hypoxia or even death.
2. Oligohydramnios: with its sequelae particularly cord compression during labor.
3. Obstructed labor: due to;
– oversized baby,
– no molding of the skull due to more calcification.
4- Increased incidence of operative delivery.
Diagnosis
(A) Antenatal:
– History: calculation of gestational age (see later).
– Examination: larger baby size.
– X-ray: large ossification center in the upper end of the tibia.
Ultrasonography: can detect,
– Biparietal diameter more than 9.6 cm.
– Increased fetal weight.
– Oligohydramnios.
– Increased placental calcification.
– Tests for placental function (see later).
(B) Postnatal:
– Baby length: more than 54 cm.
– Baby weight: more than 4.5 kg.
– Skull: well ossified with smaller fontanelles.
– Fingernails: project beyond fingertips.
Management
Termination of labor is indicated which may be by:
a.Induction of labor if the condition is favorable for vaginal delivery
b.Cesarean section: if conditions are not favorable for vaginal delivery, or if induction of labour failed.