PRETERM LABOR : Incidences & Causes

 

Preterm labor refers to the onset of uterine contractions of sufficient strength and frequency to effect progressive dilatation and effacement of cervix between 20 and 37 weeks of gestation.

Incidences:

           Overall incidence of preterm labor is reported to be 6-15% and 4-50% of these occur spontaneously, whereas 25% occur following preterm pre-labor rupture of membranes (PPROM).

           Iatrogenic (resulting from the activity of physician) preterm labor due to obstetric intervention to avoid maternal or fetal compromise, accounts for about 25%.

 Causes :

Maternal causes:

n  Racial – its seen more in black because of the reason of low socio economic condition.

n  Maternal age – both the extremes of  reproductive age that is below 18 and above 40 yrs are at greater risk.

n  Maternal weight –

n  Maternal weight less than 45 kgs this indirectly points towards the maternal nutritional level.

n  Socioeconomic status – associated with inadequate antenatal care, poor nutrition. 

n  Substance abuse –

n   Smoking  (nicotin –  vasoconstirction –  uteroplacental insufficiency )

n  Alcohol

n  Tobacco

n  Trauma –

n     Coitus  - prostaglandins released during coitus and those present in the seminal fluid can lead to preterm uterine contractions.              

n  Strenuous work

n  Psychological - personal  stress

n  Chronic ill health

Iatrogenic (resulting from the activity of physicians)

 

  n  Elective induction – with consideration to maternal illness, wrong calculation of GA (gestational age)

n  Previous induced abortion

n  Past history of preterm labour

n  Short interval between pregnancies

n  PROM (premature rupture of membrane)

n   Chorioamnionitis (inflammation of the fetal membranes)

 

Medical and obstetrical conditions

n  Anaemia 

n  Diabetes mellitus

n  Asthama

n  Pre eclampsia, eclampsia (complication of pregnancy)

n  Chronic HTN (hypertension)

n  Antepartum hemorrhage (bleeding during pregnancy)

n  Infection – pneumonia, UTI, asmptomatic bacteriosis, pylonephritis, reproductive tract infection like bacterial vaginosis, appendicitis, dental infections. 

 

Uterine and cervical factors:

n  Congenital abnormalities – septate, unicornuate, bicornuate uterus (congenital malformations of uterus)

n  Uterine over distention – hydramnios, multiple pregnancy, fibroids.

n  Incompetent cervix – following conization, spontaneous or induced miscarriage. 

n  Placental factors:

                abnormalities in placenta (placenta previa, abruptio placenta)

 

Fetal factors :

Ø   Congenital malformations – fetal hydrops, polyhydramnios (excess of amniotic fluid )

Ø  IUD (intrauterine devices)

Ø  Genetic