Perinatal definitions

Perinatal definitions

Gestational age (post-menstrual age) 

Age measured from the first day of the last menstrual period before conception and expressed in com-plete weeks or days.

Chronological/postnatal age Time elapsed from birth.

Corrected age Chronological age minus the number of weeks born before 40wks gestation.

Spontaneous abortion (miscarriage) 

A conceptus born after spontaneous labour without any signs of life before 24 completed weeks gestation.

Live birth 

A baby that displays any sign of life (i.e. breathing, heart beat, cord pulsation, or voluntary movement) after complete delivery from the mother, irrespective of gestation.

Stillbirth (late foetal death) 

Foetal death prior to complete delivery from the mother after 24 completed weeks gestation.

Perinatal mortality 

Includes all stillbirths and neonatal deaths in the first week. UK rate 77–8 per thousand total births.

Neonatal mortality 

Death amongst live births before 28 days of age (whatever the gestation at birth). UK rate 73 per thousand live births.

Neonatal period

From birth to 28 postnatal days in term infants. If preterm, from birth to 44wks post-menstrual age.

Preterm

Birth before 37 completed weeks gestation. 78% of births.

Term birth 

Between 37 and 42 completed weeks gestation.

Post-term (post-mature) 

Birth after 42 completed weeks gestation. <5% of births.

Low birth weight (LBW) 

Birth weight <2500g. 7% of births.

Very low birth weight (VLBW) 

Birth weight <1500g. 1.2% of births.

Extremely low birth weight (ELBW) 

Birth weight <1000g.

Small for gestational age (SGA) 

Birth weight <10th centile for ges-tational age.

Large for gestational age (LGA) 

Birth weight >90th centile for ges-tational age.