Affiliations:
Department of Obstetrics and Gynecology, Women and Children’s Hospital
of Chongqing Medical University, Chongqing 401147, China.
Correspondence: ** Tai-Hang Liu (liuth@cqmu.edu.cn); * Xia Lan
(18623177325@163.com). Women and Children’s Hospital of Chongqing
Medical University, No. 120 Longshan Rd, Yubei District, Chongqing,
401147, China. Tel: +86 23 63840868
Conflict of Interest Disclosures: None reported.
Authors’ contributions: Contributor W. Tang was responsible for
the organization and coordination of the trial. T. Liu was the chief
investigator and responsible for the data analysis. W. Tang, T. Liu and
X. Lan co-wrote the manuscript. All authors contributed to the writing
of the final manuscript.
Financial support: This study did not receive any specific
funding.
After a thorough analysis of the latest research by Julia Sanders et al.
on severely obese adolescents, we are encouraged by the finding that
waterbirth with the use of warm water immersion for analgesia in women
without antenatal or intrapartum risk factors does not increase the
incidence of obstetric anal sphincter injuries (OASI) or adverse
neonatal outcomes compared to births that occur out of
water1. However, we believe there are key potential
issues that may affect the interpretation of the study results.
Firstly, the study did not explicitly adjust for the potential impact of
twin or multiple pregnancies in its analysis. Although the study
excluded women with antenatal or intrapartum risk factors, it did not
specify whether twin or multiple pregnancies were considered. Twin or
multiple pregnancies significantly increase the stress on the birth
canal during delivery, especially on the anal sphincter, as they need to
accommodate and deliver multiple fetuses. This increased pressure can
lead to excessive stretching and tearing of the birth canal tissues,
thereby affecting the risk of OASI2. Additionally,
multiple pregnancies may prolong the labor process, especially the
second stage, as multiple fetuses need to be delivered consecutively,
further increasing the risk of trauma to the birth canal. Moreover, the
significant expansion of the uterus and birth canal caused by multiple
pregnancies could affect the integrity of the birth canal and the
function of the anal sphincter. Concerning the postpartum hemorrhage, a
particular focus of waterbirth studies, multiple pregnancies are more
common than singleton pregnancies, which is related to an increased risk
of uterine atony, a primary cause of obstetric hemorrhage. At the same
time, multiple pregnancies lead to increased maternal blood volume and
uterine blood flow to support the additional uterine, placental, and
fetal tissues. The unique factors of twin or multiple pregnancies, such
as differing chorionicity and discordant fetal growth, could also
significantly affect the reliability of the study’s
conclusions3.
Secondly, the study did not record in detail the mode of onset of labor,
the duration of labor, the duration of immersion in warm water, and the
use of pharmacological analgesia, which are factors widely considered in
previous waterbirth research4. Not recording whether
labor started naturally or was induced could affect the assessment of
the labor process and the need for interventions. Induced labor may
increase the risk of OASI because it can involve more intense
contractions and a shorter cervical dilation period. Also, not recording
the duration of the three stages of labor and the details of
pharmacological analgesia use may limit the assessment of labor
progression, pain management, maternal comfort, and a more comprehensive
outcome, which could also affect the labor process and the initial state
of the newborn. In summary, although the study’s conclusions by Julia
Sanders et al. are somewhat encouraging, further analysis and resolution
of the above issues will help to enhance the credibility and validity of
the study’s conclusions.