February 27, 2014 — Summary of "Beyond Labor: The Role of Natural and Synthetic Oxytocin in the Transition to Motherhood," Bell et al., Journal of Midwifery & Women's Health, Jan. 28, 2014.
Recent research raises questions about how the use of synthetic oxytocin, including Pitocin and Syntocinon, during childbirth potentially affects the endogenous oxytocin system and maternal mood, stress reactivity and mothering behaviors, including lactation, according to a review led by Aleeca Bell of the Department of Women, Children and Family Health Science at the University of Illinois at Chicago College of Nursing.
The researchers explained that the endogenous oxytocin system is a key element in women's transition to motherhood because it influences molecular pathways that inhibit stress reaction, stem positive moods and promote positive mothering behaviors.
Although synthetic oxytocin has proven benefits and is widely used in labor and postpartum care, little evidence exists on its biological and behavioral effects. To learn more about these possible interactions, the researchers reviewed findings from various studies on the effects of synthetic oxytocin on women's transition to motherhood.
Functions of Endogenous Oxytocin
The endogenous oxytocin system undergoes "[p]rofound changes" during pregnancy, with peptide oxytocin accumulating in the woman's posterior pituitary until term, when "inhibitory mechanisms are removed for labor to occur." In addition, oxytocin receptors (OTR) located in the uterine muscles increase as the body prepares for surges of the hormone to be released during birth.
Challenges in Examining Oxytocin's Molecular Effects
According to the researchers, it is difficult to assess the effects of Pitocin on a molecular level for several reasons, including that its half-life is believed to be just a few minutes. Additionally, a particular dose "may or may not" directly result in a certain uterine contraction pattern, and "oxytocin levels in plasma cannot always be interpreted as being meaningful in a particular effect on brain activity."
Further complicating the matter is the fact that oxytocin in the central nervous system is continuously produced within the spinal cord and brain, while also being released in pulses by the posterior pituitary into the bloodstream. It also has not been conclusively determined "whether peripherally administered oxytocin ... crosses the blood-brain barrier," the researchers noted.
It also is unknown "[w]hether the maternal brain will reliably respond to exogenous oxytocin by decreasing or increasing the synthesis or release of endogenous oxytocin," they added. Further, more research is needed to explore how synthetic oxytocin affects the "capacity of the OTR to become saturated," the researchers wrote.
Effects on the Transition to Motherhood
The postpartum period brings "drastic hormonal shifts, transition to motherhood, coping with new stressors, physical pain, lactation, and attachment -- all of which involve the endogenous oxytocin system," the researchers wrote. A "difficult transition to motherhood" could potentially "lead to dysregulated stress reactivity, mood disturbances, susceptibility to less sensitive mothering, asynchronous mother-infant interaction, and poor infant attachment," they noted.
Adaptions in the maternal oxytocin system provide protection from stress and the demands of the perinatal period, according to the researchers. High levels of oxytocin during childbirth mitigate stress hormones released by pain and fear, some studies suggest.
Oxytocin pulses in the brain also increase during lactation, allowing women to "react less to stressors and display less anxiety-like behavior than nonlactating females," according to the researchers. Further, oxytocin measurements in lactating women's saliva shows that "oxytocin may increase prior to feeding, when women are preparing to breastfeed."
Research also suggests that a well-regulated oxytocin system can help protect against negative maternal moods. However, it is difficult to determine whether "intrapartum synthetic oxytocin confers the same protective function as endogenous oxytocin on maternal mental health," according to the review.
In addition, it is not known whether synthetic oxytocin exposure during labor affects moods postpartum. The researchers contended that "based on ... knowledge of the actions of oxytocin in other situations and in tissues outside the central nervous system, [they] would anticipate that any effects of synthetic oxytocin would be dose dependent and would show individual differences, influenced by context and the history of the mother."
Meanwhile, growing evidence points to a link between oxytocin and "optimal mothering behaviors," including, "affectionate touch, eye-to-eye contact, positive affect, and affectionate language." Similar relationships also have been found between less optimal mothering behaviors and atypical peripheral oxytocin levels. The researchers noted that "it is unclear if any of these relationships are derived or influenced by the birth experience or use of synthetic oxytocin. However, these findings do suggest that oxytocin plays a key role, beyond labor, in the transition to motherhood."
The researchers concluded that there is still much "to be understood about the role that oxytocin plays in the transition to motherhood" and noted that "emerging research in both animal and human models highlights the need for a deeper understanding."
Because the effects of oxytocin "have not been investigated thoroughly in the context of human birth care," they recommended that "[m]idwifery and obstetric research should consider the oxytocin system as a whole, not just the immediate clinical result, when investigating the role of physiologic birth as well as birth interventions on biobehavioral outcomes in mothers and infants."