Oxytocin in prematurely born infants and their parents - A systematic review with clinical implications.

Introduction: The neuropeptide oxytocin (OT) is considered an important regulatory factor in mother-child bonding after birth. It is also thought to have neuroprotective effects, which could be particularly important for preterm born (≤ 37 weeks) infants, who are considered a high-risk group for several health issues. They are born when their own and their mother's OT-concentrations have not yet reached their maximum during pregnancy and often require neonatal intensive care, separating them from their parents. This review aims to identify studies on OT-concentration in preterm infants and their parents as well as to investigate possible influences on their OT-secretion.

Methods: The systematic literature search was conducted according to PRISMA guidelines, using the keywords "oxytocin", "infants", "prematurely" and synonyms in the PubMed, ScienceDirect, Google Scholar and PsycInfo databases. 15 publications met the criteria. As the studies were very heterogeneous in terms of the methods applied for the analysis of oxytocin concentration, a narrative synthesis and just a partial meta-analysis was performed.

Results: The quantification methods of OT were heterogeneous, the reported maternal values ranged from 1 to 4000 pg/ml. The sample sizes were limited (mean n = 31 across all studies) and OT was mostly measured in infant saliva. In the intervention studies, a consistent positive relationship was found between OT-concentration and physical contact, stress reduction and attachment behavior. A meta-analysis was performed for the effect size of bonding interventions like SSC on OT in maternal saliva, revealing a medium effect size (SMD = 0.40, p = 0.002).

Discussion: Despite the variance in methods and a certain risk of bias which limits the reliability of the studies, the overall results suggest an increase in oxytocin concentrations in response to bonding interventions like skin contact in preterm infants and their parents. Both appear to benefit from these anxiolytic and stress-reducing measures, supporting the clinical application of Kangaroo care in preterm infants. Methodological issues related to OT assessment in different body fluids of prematurely born infants are critically discussed. Future studies, applying an open-science approach, should focus on longitudinal designs, inclusion of control groups and confounding variables to ensure reliability and comparability.