Childbirth is one of the most painful events that a woman is likely to experience, and thus is a major concern for most parturient. Severe pain releases stress mediators and may thus compromise fetus well-being if placental perfusion is decreased. Epidural analgesia is the golden standard for the management of severe labor pain. However, it could not always be used both due the parturient related factors and the organizational reasons.However, the knowledge on safety and efficacy of oxycodone involving mother, fetus and newborn is limited.

Aim of the study is firstly, to evaluate the efficacy and safety of oxycodone in labor pain healthy parturients. Secondly, to measure parturient's blood oxycodone concentration during labour and fetal concentration from placental umbilical vein and artery right after birth.

Inclusion Criteria:

• Labouring healthy women
• Early labour
• Age 18-45 years

Exclusion Criteria:

• Sleep apnea or other central deficit affecting breathing
• Pulmonary insufficiency
• Liver of kidney insufficiency
• Use of mono amine oxidase medication
• Thyroid, pituitary insufficiency
• Paralytic ileus
• Other contraindication specified by the investigator