Final answer:
Braxton Hicks contractions are irregular and felt in the abdomen or groin, but do not contribute to cervical effacement and dilation, nor are they intensely painful or regular and progressive like true labor contractions are.
Step-by-step explanation:
The perinatal nurse would describe prelabor or Braxton Hicks contractions to the prenatal class attendants as irregular contractions that are felt in the abdomen or groin. These contractions are distinct from the true labor contractions which are regular, powerful, and become more frequent over time. Braxton Hicks contractions do not contribute to cervical effacement and dilation which are significant changes leading up to childbirth, characterized by the progressive thinning and opening of the cervix in preparation for delivery. Unlike true labor, Braxton Hicks contractions are not intensely painful and do not exhibit a pattern of increasing intensity or frequency. They can often be relieved through hydration or rest, whereas true labor contractions persist and strengthen irrespective of such measures.
During true labor, uterine contractions become more regular and progressive as oxytocin levels rise, leading to cervical dilation and effacement, ultimately progressing to the birth of the baby. Therefore, the correct descriptions of Braxton Hicks contractions are they are felt in the abdomen or groin (B) and irregular (D), but not contributing to cervical effacement and dilation (A), intensely painful (C), or regular and progressive (E).