The study looked at 34 healthy women in their second trimester of pregnancy who were undergoing amniocentesis. The study examined amniotic fluid corticotropin-releasing hormone and urocortin for their predictive value when it came to fetal growth and neonatal outcomes. The study recognised amniocentesis as a stressor and involved both salivary cortisol tests and “chronic social overload” surveys filled out by the mothers. 
The results of the study showed interesting links between the concentrations of stress hormones in the amniotic fluid and the size and development of the fetus. Essentially, “physical stress to the mother can change the metabolism in the placenta and influence the growth of the unborn child [1, 2].” The impact appeared to be on size of the fetus at the expense of organ maturity.
We know that the human body releases stress hormones to handle times of peak pressure. One of these is corticotropin-releasing hormone or CRH that goes on to increase the stress hormone cortisol. It turns out the placenta can also emit CRH, affecting fetal metabolism via the amniotic fluid. This isn’t always a bad thing. In fact, it seems to be a protective factor readying the mother and baby for the potential of early labour.
“Animal studies have shown that this hormone can boost the development of the unborn child: Unfavorable growth conditions in the woman lead to an increased release of the hormone, thereby improving the chances of survival in case of a premature birth. Under certain circumstances, however, this increase can also have negative consequences. ”
What the Zurich study revealed was that “An excessive acceleration of growth may occur at the expense of the proper maturation of the organs (Ulrike Ehlert, psychologist and program coordinator via Science Daily) .”
There is good news though! The affect seems to be true only for long-term stress. Short-term stress appeared to have no effect. Ehlert concluded that, “the baby obviously remains protected against negative effects in case of acute, short term stress to the mother .”
It is not always possible to avoid chronic stress during pregnancy, but the psychologists at work on this study emphasise that there are a couple of factors that can help. One of them is support from a therapist who can help you handle the stress better. Lead researcher Pearl La Marca-Ghaemmaghami also remarked that, “a secure bond between the mother and child after the birth can neutralize negative effects of stress during pregnancy .”
While further work needs to be done in order to clarify the exact mechanisms by which CRH affects fetal growth and development, it is certainly an interesting line of investigation. This proves one thing for sure – anything we can do to enhance the expectant mothers feelings of support, connectedness and wellbeing is a good investment in the health of her unborn child.
 Pearl La Marca-Ghaemmaghami, Sara M. Dainese, Günter Stalla, Marina Haller, Roland Zimmermann, Ulrike Ehlert. Second-trimester amniotic fluid corticotropin-releasing hormone and urocortin in relation to maternal stress and fetal growth in human pregnancy. Stress, 2017; 1 DOI: 10.1080/10253890.2017.1312336
 University of Zurich. “Too much stress for the mother affects the baby through amniotic fluid.” ScienceDaily. ScienceDaily, 29 May 2017.