Previous research suggests that when a fixed interval is interrupted (known as the gap procedure), pigeons tend to reset memory and start timing from 0 after the gap. However, because the ambient conditions of the gap typically have been the same as during the intertrial interval (ITI), ambiguity may have resulted. In the present experiment, the authors found that when ambient conditions during the gap were similar to the ITI, pigeons tended to reset memory, but when ambient conditions during the gap were different from the ITI, pigeons tended to stop timing, retain the duration of the stimulus in memory, and add to that time when the stimulus reappeared. Thus, when the gap was unambiguous, pigeons timed accurately.

Introduction Although the safety of water immersion during labor is largely supported by evidence from research, the risks to women and neonates during waterbirth are not well established. The purpose of this study was to generate evidence regarding maternal and neonatal outcomes related to water immersion in labor and during birth. Methods A retrospective cohort study included a convenience sample of women receiving prenatal care at a nurse‐midwifery practice. Participants were categorized into 3 groups: 1) waterbirth, 2) water labor, or 3) neither. Participant characteristics, maternal outcomes, and newborn outcomes were collected at time of birth and health record abstraction. At the 6‐week postpartum visit, another maternal outcome, satisfaction with birth, was measured using the Care in Obstetrics: Measure for Testing Satisfaction (COMFORTS) scale. Analysis included effect size, descriptive statistics (sample characteristics), and maternal and neonatal group differences (analysis of variance and chi‐square) with a significance level of P < .05. Results Women in the waterbirth (n = 58), water labor (n = 61), and neither (n = 111) groups were primarily white, married, and college educated and did not differ by age or education. Women in the waterbirth group were more likely to be multiparous. Nulliparous women who had a waterbirth had a significantly shorter second stage of labor than nulliparous women who did not have a waterbirth (P = .03). The most commonly cited reasons for discontinuation of hydrotherapy were maternal choice (42.6%) and need for pain medication (29.5%). Significantly more women in the waterbirth group experienced a postpartum hemorrhage, compared with water labor or neither (n = 5, n = 3, n = 1, respectively; P = .045); there was no difference in related clinical measures. Neonatal outcomes were not significantly different. Maternal satisfaction was high across all groups. Discussion The results of this study suggest that waterbirth, attended by qualified intrapartum care providers in hospital settings in the United States, is a reasonable option for low‐risk women and their neonates.

Offspring born preterm (ie, before 37 weeks of gestation) are more likely to die or experience long-standing illness than full-term offspring. Maternal genetic variants (ie, heritable, stable variations in the genetic code) and epigenetic modifications (ie, chemical modifications to the genetic code that can affect which genes are turned on or off) in response to stress have been implicated in preterm birth. Fetal genetic variants have been linked to preterm birth though the role of offspring epigenetics in preterm birth remains understudied. This systematic review synthesizes the literature examining associations among stress during pregnancy and epigenetic modifications to offspring DNA, with 25 reports identified. Ten reports examined DNA methylation (ie, addition/removal of methyl groups to/from DNA) across the epigenome. The remainder examined DNA methylation near genes of interest, primarily genes linked to hypothalamic-pituitary-adrenal axis function (NR3C1, FKBP51), growth/immune function (IGF2), and socioemotional regulation (SLC6A4, OXTR). The majority of reports noted associations among stress and offspring DNA methylation, primarily when perceived stress, anxiety, or depression served as the predictor. Findings suggest that differences in offspring epigenetic patterns may play a role in stress-associated preterm birth and serve as targets for novel interventions.