Getting into the water: a prospective observational study of water immersion for labour and birth at a New Zealand District Health Board

The DHB maternity services include a tertiary-level maternity unit in a New Zealand city (average 3800 births per year) plus two midwife-led units (MLUs) (one at 30 mins and the other at 60 min away from the tertiary referral unit). At the tertiary maternity unit, there are 12 birth rooms each with the same design features, including a birth pool or bath, included in the new hospital design commissioned in 2009. The room size and layout differ slightly. Five rooms have a purpose-built birth pool while the remaining seven rooms have baths permanently installed in the corner of the room. The birth pools are round, 1200 mm in diameter and 650 mm deep. There is access around 66% of the pool, a shower, two handrails and steps into the pool. The baths are five-sided and are bound on two sides by a wall. The sides alongside the wall measure 1480 mm, the two short slides measure 670 mm and the front access side measures 1080 mm. The depth of the bathtub is 510 mm. There is a hand-held mixer shower hose set plumbed in over the bath, four handrails, a sieve and thermometer and easy access to piped oxygen, suction and Entonox. At MLU 1 there is one bath measuring 1000 mm wide × 1840 mm long and 630 mm deep. The bath is in a separate room attached to two birth rooms. There is access around three sides of the bath, inner armrests and a headrest. All pools use a disposable liner. For comfort, a soft mat under the liner, and a floor mat are available for comfort for kneeling/laying on the floor around the bath. Equipment in the bathroom includes: a sieve, thermometer, a large mirror and an electric oil burner, portable oxygen, suction and Entonox are available. At MLU 2 there is one bathroom with a purpose-built birth pool permanently installed towards the corner of the room adjacent to the only birth room. The birth pool is rectangular, measuring 1020 mm wide, 1350 mm long and 740 mm deep. There is a built-in seat which can also be used as a step to get in and out, with access around three sides of the pool.

Women who used the birth pool or bath during labour and birth across all three DHB maternity facilities, initiated at the time the new tertiary unit opened in February 2009 through to March 2014. Criteria for the use of water immersion for labour and birth usage, as outlined in the DHB guideline, as at least 37 weeks gestation, no adverse fetal or maternal factors in the pregnancy, an informed choice, established labour (judicious use for women with long latent labour is useful to promote relaxation) when there has been a diagnosis of labour dystocia (before using oxytocin). Ruptured membranes are not a contraindication for the use of the birth pool or bath.

A paper-based data collection tool, included in the medical record of all women booked to birth at each of the three facilities, was adapted from the DHB water immersion guideline and the literature on water immersion. The form captured details of place of birth, type of caregiver and type of water facility as well as maternal characteristics (such as parity and gestation); and intrapartum events and interventions (such as labour onset, membrane rupture, vaginal examinations, pain relief). Maternal outcomes (such as length of labour, mode of birth, estimated blood loss, third stage technique, perineal or vaginal wall tear, labial tear, episiotomy, suturing) and neonatal outcomes (Apgar scores and NICU admission) were included (see supplementary file 1).

Lead Maternity Care (LMC) midwives or core (hospital employed) midwives were asked to complete the form for each woman who used water immersion during labour or birth. Midwives could also enter the presence of any risk factors from the current or previous pregnancies. Data were manually entered in Excel spreadsheet by the primary investigator and research assistant and transferred to SPSS Version 23 for analysis. Where data was unclear or missing, a review of other DHB data sources such as the DHB Patient Information Management System (PIMS) and clinical records of women and neonates (if admitted to Neonatal Intensive Care Unit (NICU) post-birth) occurred. The denominator of some variables differs given missing data.

Descriptive statistics describe the characteristics of women who used water immersion during labour and birth and to describe the women and infants’ birthing outcomes. Frequencies and percentages were calculated for categorical variables, mean and standard deviation for continuous variables.

The New Zealand Health and Disability Ethics Committee (Approval number 15/CEN/55) provided research ethics approval.

From the 1517 women who used water immersion for labour and birth there were 584 (38.5%) water births. More than half (53.7%) of the water births occurred in multiparous women whereas only a quarter (25.9%) of nulliparous had a water birth. Overall, the rate of spontaneous vaginal birth was 84% with 9.4% assisted deliveries and 6.5% caesarean sections. The proportion of assisted birth/CS was significantly higher in nulliparous (25.7%) than in multiparous (4.2%) (p = < 0.001) (Table 1).

A quarter of the women had an artificial rupture of membranes (ARM). More than a third (n = 555, 36.6%) of women in this study used pain relief after leaving the pool or bath (Table 1). The pharmacological pain relief commonly used were Inhalation/Entonox, Epidural, and Opioid. Alternative and complementary therapies used were transcutaneous nerve stimulation (TENS), acupuncture, acupressure, homeopathy, massage, and heat-pack.

The mean duration of the first stage of labour was 330 mins (SD 238), the second stage of labour was 55 mins (SD 62) and the third stage of labour was 16 mins (SD 17) (Table 1).

Women generally preferred to adopt a semi-reclined (41.7%) or a hands and knees position (15.8%) for birth. Placental birth was actively managed in 917 (60.4%) women whilst 594 (39.2%) has a physiological third stage. Estimated blood loss below 500mls was recorded for 1322 (87.1%) women, with 13 (0.9% of women experiencing a post-partum haemorrhage of greater than 1500mls (seven following spontaneous vaginal birth and nine following operative birth).

Nearly 43% of women had an intact perineum following birth with first- and second-degree perineal tears being most common (25.7 and 27.4% respectively). Severe perineal trauma (3rd and 4th degree tears combined) occurred for 35 (2.3%) women most during spontaneous vaginal birth, including the two 4th degree tears.

Most neonates had an Apgar score greater than or equal to seven at both 1 min and 5 min post-birth (93.7 and 98.8% respectively). Only 37 (2.4% of neonates required admission to NICU following birth. The reasons for NICU admission were recorded as low Apgar scores following shoulder dystocia, non-breathing, grunting, flat baby, respiratory problems, and meconium aspiration. There were no neonatal deaths (Table 1).

The tertiary maternity unit was the most common planned birthplace for the women in this study at 78%. More than half of nulliparous women (n = 704, 59%) chose the tertiary maternity unit for their birthplace over MLU 1 and MLU 2 (n = 67, 41% and n = 59, 36% respectively), whereas more multiparous women chose MLU 1 and MLU 2 (n = 97, 59% and n = 106, 64% respectively) over the tertiary maternity unit (n = 484, 41%). Midwifery-led units were more likely to adopt water birth than at the tertiary unit: approximately two-thirds of women who used water immersion during labour, both in MLU 1 and MLU 2, had a water birth (n = 106, 65% and n = 108, 65% respectively) however less than a third of women using water immersion at the tertiary maternity unit had a water birth (n = 370, 31%) (Table 2).

As expected, all births in the midwife-led units were Spontaneous Vaginal Births (SVB). The gestational age at start of labour was similar across all settings. The use of pain relief during labour differed by place of birth: before entry to the pool/bath 493 (41%) of women in a tertiary maternity unit used pharmacological pain relief, whereas women in the midwife-led units used less (33 and 22% respectively) (Table 2).

In keeping with the strong association between water birth and physiological third stage of labour, 63% (n = 103) of women had a physiological third stage of labour at MLU 1 and 50% (n = 82) at MLU 2. In the tertiary maternity unit 65% (n = 775) of women had an actively managed third stage of labour even.

A second-degree perineal tear was most common across all birth places with 30% at the tertiary unit, and 20 and 15% at the two midwife-led units respectively. Episiotomy was rarely used at the midwife-led units. Women in the tertiary maternity unit, where the water birth rate was much lower than MLU 1 and MLU 2, showed higher numbers of episiotomy and suturing than women in the MLUs (Table 2).

The Apgar scores at 1, 5 and 10 min across all the birth places were most usually ≥ seven. Most neonates born to women who used water immersion for labour and birth did not require admission to NICU (98%).

The results presented are from a sample of women who gave birth in one DHB in New Zealand, and as such, the findings are only indicative of the practice in these settings. The results might not represent all women who used water immersion for labour and birth at the DHB during the time frame of this study. Anecdotally, during the study period, we were aware that not all midwives completed documentation all the time, but were unable to establish the extent of this, nor to enforce it. No data for maternal age or ethnicity were collected. A further limitation is the lack of a control group of low-risk women who met the eligibility criteria but did not use the bath or birth pool during labour. To reduce the proportion of missing data, a review of the PIMS and the clinical records occurred.

The differences in outcomes by place of birth should prompt a discussion around what else is happening to impact the decisions of women and midwives. Focused education on water immersion for labour and birth for all midwives and doctors is warranted as well as antenatal education that provides evidence for the impact of place of birth and caregiver on outcomes for women and babies.

More research is required to explore factors impacting on women’s decision-making around the use of water immersion for labour and birth as well as women’s satisfaction. It would be beneficial to explore the factors influencing midwives to offer water immersion for labour and birth, and the barriers and facilitators to offering this service in the tertiary maternity environment.