Previous research has shown that post-partum abdominal pain is greater in multiparous than primiparous women (Murray and Holdcroft, 1989). Although breast feeding in the immediate post-partum period induces uterine contractions and abdominal pain, it is unknown how parity influences the contractions. Here, a structured questionnaire that included the McGill Pain Questionnaire (total pain intensity index, TPI) and visual analog scales (VAS) was used to evaluate the intensity, location, referred tenderness (hyperalgesia), descriptor, and temporal characteristics of pain during breast feeding up to three days after uncomplicated vaginal delivery. Three groups of women were studied: primiparous (n=25); low parity (1-2 prior births; n=14); high parity (3-5 prior births; n=11). Uterine contractions during breast feeding were recorded using tocodynamometry in some women from each group (n=17, 6, 7, respectively). For comparison, an identical questionnaire was used to evaluate pains the women remembered experiencing during menstruation in the year immediately preceding the current pregnancy. During breast feeding, nearly all women (96%) reported deep pain primarily at three sites: lower abdomen, low back, and breast, with associated referred hyperalgesia in 62% of them. The intensity of these pains increased significantly with parity (P<0.001), along with an increase in the number of pain sites (P=0.03), mainly in lower abdomen and back, but not breast. Similarly, both the mean duration and number of uterine contractions increased significantly with parity (P<0.001). Furthermore, the mean duration of contractions correlated significantly with the pain scores (P=0.03 [VAS] and P=0.006 [TPI]). In contrast with pain during breast feeding, the intensity of pain during menstruation did not change with parity. These results demonstrate that pain, referred pain, and uterine contractions during breast feeding in the immediate post-partum period increase with parity, suggesting that childbirth can induce central neural changes that increase predisposition for pain during the post-partum period.

• R01 NS 11892/NS/NINDS NIH HHS/United States