Preterm and critically ill neonates experience many painful manipulations. The aim of the study is to evaluate the influence of these experiences and maternal deprivation on later pain behavior. Using Scoring systems, Prechtl general movements, skin conductance, testing flexor reflex levels with von Frey filaments and measuring salivary cortisol levels the investigators compare pain behavior of preterm (birth weight (BW) < 1500 grams), term neonates with need of ventilation (> 48 hours) with healthy neonates at the time of their first vaccination at the age of 3-4 months. The investigators are also testing flexor reflexes and skin conductance and general movements in regular intervals during the initial hospital stay. The investigators hypothesize that pain behavior is different at the age of 3-4 months in children with many early painful experiences.