We found a significantly reduced risk of caesarean delivery for women giving birth in a sensory delivery room compared with a standard delivery room. Furthermore, the need for oxytocin infusion was lower in the group giving birth in a sensory delivery room vs. a standard delivery room. The frequency of having an acute caesarean delivery for the Robson 1 group was 9.7% in Denmark between 2009–20113. The caesarean delivery rate among the Robson 1 group in this period at the Department of Obstetrics and Gynaecology at Northern Zealand Hospital Hillerød was 9.0%. In our study group, the caesarean delivery rate was 10.7% in the standard delivery room. When evaluating stimulation with oxytocin during birth, our univariate analysis suggested equal use among women giving birth in the two types of delivery rooms (30.4% in sensory delivery rooms vs. 34.5% in standard delivery rooms). These unadjusted percentages are comparable to the average use of oxytocin stimulation during birth in hospitals in Denmark4. However, when adjusted for potential important confounders, the estimated risk for this outcome nearly reached statistical significance. We found the two groups, giving birth in either the sensory or the standard delivery room, were comparable as no difference was observed between baseline characteristics. In only one case, a woman changed from a standard to a sensory delivery room during labour when it became available. She was recorded as giving birth in a standard delivery room. To our knowledge, this study is the first to highlight the potential positive effects of giving birth in a sensory delivery room.

A potential weakness of the study is its observational nature. To some extent, the women in labour were assigned by midwifes to either a sensory delivery room or a standard delivery room. The midwives could potentially select women who were more likely to have an uncomplicated birth to the sensory rooms since they were more likely to enjoy the full potential of the room, and women with more complicated labour to the standard delivery room. This would be a potential selection bias. To explore this potential bias, 10 midwifes of approximately 60 on the labour ward at the Department of Obstetrics and Gynaecology at North Zealand Hospital, Hillerød, were randomly asked if they selected or had any preferences for women to give birth in either of the two types of delivery rooms. All midwifes answered that they did not make any selection, and that the two sensory rooms (of the 10 delivery rooms) at the hospital were the first to be chosen either by the woman in labour or the midwife; thus, they were consequently used more often. Additionally, we only included nulliparous women with fetuses in the cephalic position who were in spontaneous labour at term (Robson 12) in the study. The systemic classification into a Robson group2 by midwifes or doctors was not done when the pregnant woman arrived at the hospital in labour. This supports the notion of a random selection of women to the sensory delivery rooms.

In the present study we do not have any information on Body Mass Index (BMI) at the time of labour. Hereby, we cannot guarantee that the two groups are equally divided concerning BMI. It is well-documented that obese women have a higher risk of acute caesarean delivery and a lower probability for a normal vaginal delivery5. Studies suggest most primiparous births commence at night or in the early morning hours1. In the morning, melatonin excretion is maximal. Melatonin is a hormone6 produced in the pineal gland that has a 24-h secretory rhythm. This rhythm is driven by an endogenous circadian oscillator in the suprachiasmatic nucleus (SCN) of the hypothalamus7. A neuronal pathway connects the SCN with spinal nuclei of sympathetic neurons that activate the pineal gland. The neuronal connection from the retina to SCN (via the retinohypothalamic tract) imparts the suppressive effect of the light and the involvement of the melatonin secretory rhythm on the light-dark cycle8. Oxytocin is produced in the hypothalamus and excreted from the posterior pituitary gland. Oxytocin is the most important hormone in initiation of labour and acts synergistically with melatonin9. Like oxytocin, melatonin has its own receptors on the uterus capable of providing contractions. These receptors interact with each other and, along with additional hormones, induce contractions of the uterus9. There are several published studies on circadian rhythm and initiations of births9. Light that inhibits melatonin secretion is blue (446–477 nm) or white at high illuminance (around 10,000 lx) and red/yellow light (625–740 nm) is believed to have a non-suppression effect on melatonin10,11.

Labour is traditionally divided into three stages. In labour, and several hormones play essential roles. These hormones includes prostaglandin, oxytocin, melatonin, and adrenaline10. Studies suggest that adrenaline has a prolonging effect in stage 1 of birth11. Oxytocin, prostaglandin, and melatonin are important hormones regarding for uterine contractions and are therefore essential in all three stages12.

In 2014, Olcede J. et al.13,14 published a pilot study on pregnant volunteers (>38 weeks of gestation) and performed continuously monitoring for uterine contractions from 7:00 PM until 7:00 AM under dim light. At 11:00 PM, a 10,000 lux full- spectrum lamp, one meter from the participants’ eyes was activated for one hour to suppress melatonin secretion15. Among the volunteers exposed to light, the nocturnal contraction frequencies were either partially or completely suppressed. This observation supports the idea that light levels that potentially could facilitate the secretion of melatonin. A continuous secretion of melatonin during birth could induce continuous contractions of the uterus, and hereby optimal propulsion for the women in labour. In our study, women who give birth in a sensory delivery room, theoretically would have the best conditions for a continuously secretion of melatonin and, therefore, the opportunity for optimal propulsion. Yet, we did not see any difference in the time length of birth in the two groups. This could be due to the fact because we did not record which light program was chosen, and for how long the sensory programs were applied during labour. Moreover, if the sensory programs were shut down for a period of time, or what time of day the birth took place - if it was night or day. Also, several other parameters influence the propulsion of the birth. Siw Alehagen et al.11 stated that fear and pain negatively correlated with the duration of the early phases in birth have a negative impact on the early phases of birth due to a rise in levels of epinephrine which are negatively correlated with the duration of the early phases in birth15.