A randomized, multicentre, open label trial comparing the start of the induction of labor with intravenous oxytocin according to the circadian rhythm with standard care.

Induction of labor is a common intervention in obstetrics.
In the Netherlands in around 23 percent of the women that were referred to the gynaecologist is induced. Labor is induced when pregnancy must end before the spontaneous onset of labor, usually because of increasing risks for mother or child caused by for example maternal illness like hypertension, preeclampsia, diabetes, prolonged pregnancy, prelabor rupture of the membranes > than 24 hours. When the cervix seems favourable, amniotomy is performed and oxytocin in a drip is started and administered in an increasing dose until regular uterine contractions occur with a frequency of three to four contractions every ten minutes. In most hospitals these elective inductions start in the early morning.

The spontaneous onset of labor however is proven to have a circadian rhythm with a preferential start of labor in the evening.
When labor begins with contractions in the evening the total duration of labor and delivery shortens, and in addition less obstetrical interventions occur. The biological explanation for this phenomenon is that the myometrium of the uterus is more sensitive for maternal oxytocin in the night than in the daytime. There is good reason to believe that the results found in spontaneous labor may also count for induced labor using intravenous oxytocin.
To our knowledge there is no study investigating this hypothesis. This study investigates therefore whether induction with intravenous oxytocin starting in the evening, following the circadian rhythm, shortens the duration of labor compared to a start in the early morning and evaluates the impact on medical interventions, the condition of the child, intrapartum infections, the necessity for pain relief and the patient satisfaction with the quality of care.

Our hypothese is that induction of labor with intravenous oxytocin starting in the evening, following the circadian rhythm, shortens the duration of labor compared to a start in the early morning.

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The women who start with induction of labor in the evening (21.00 hours) are defined as the intervention group.
The control group are those women who start in the early morning (07.00 hours).

Both groups are treated by the exactly the same protocol, except for the timing of the start of induction.