Identifying decreased perinatal CBR expression in preterm delivery placentas might help doctors improve PTB prediction and, thus, improve neonatal outcomes. However, chorionic villus sampling and other placental biopsies are invasive procedures, associated with 3 – 4 % pregnancy loss and an increased incidence of PTB, according to the International Society of Ultrasound in Obstetrics and Gynecology (ISUOG) [59]. Moreover, the appropriate timing for placental tissue sampling is unknown and difficult to estimate because more than one placental biopsy could be related to a noticeably higher risk of miscarriage or PTB. In order to better assess the placental expression of CBR, a non-invasive test could be more practical. Liquid-based cytology could be used as a non-invasive perinatal method of measuring the expression level of CBR in decidual cells during pregnancy [60,61]. Several analyses of the cervicovaginal fluid showed the potential predictive value of this examination in predicting PTB [62,63], suggesting that a technique like liquid-based cytology might provide clinicians with information on physiological changes throughout pregnancy. This approach might allow for an identification of a decrease in CBR expression, signaling the onset of PTB. However, further research is needed to validate this hypothesis.