**Important definitions** [2]:

Embryo – 1–8 weeks of gestation. Foetus – 8 weeks of gestation to term. Stillbirth intrauterine/intrapartum foetal death – after the age of legal viability, i.e., born with no "signs of life." Perinatal – stillbirths + neonates in first week after birth. Early neonate – first week after birth. Neonatal period – first month after birth. Post neonatal period – between 28 days and 1 year. Infant – from 1 month of age to 1 years of age. Preterm – <37 weeks of gestation or weight less than <2500 gram at birth. Term – 37–41 weeks of gestation. Post term – >42 weeks of gestation. Small for dates weight at birth <10th centile expected for gestational age. Very low birth weight – weight at birth <1500 gram. Premature – preterm, small for dates and very low birth weight. Intrauterine growth retardation – weight/other parameters <10th centile expected for gestational age.
