(HealthDay News)  Pain beginning at delivery is rarely reported 612 months after delivery; and the postpartum period seems to protect from chronic hypersensitivity to peripheral nerve injury in rats, according to two studies published in the January issue of Anesthesiology.

James C. Eisenach, MD, from the Wake Forest School of Medicine in Winston Salem, NC, and colleagues surveyed 937 women (76% of 1,228 women interviewed within 36 hours of delivery) at two months after delivery to identify pain that began at the time of delivery, and again at six and 12 months to examine predictors of pain. The researchers found that pain was rare at six (1.8%) and 12 months (0.3%). 7% and 16.7%, respectively, of one aspect of the variability in acute post-delivery pain was explained by past history of pain and degree of tissue damage. These factors were not related to incidence of pain two months later.

Silvia Gutierrez, PhD, also from the Wake Forest School of Medicine, and colleagues examined the effect of pregnancy and delivery on peripheral nerve injury-induced hypersensitivity to mechanical stimuli in rats. For rats that underwent spinal nerve ligation at mid-pregnancy, the researchers found that hypersensitivity partially resolved after delivery, but this resolution was prevented by removal of pups. Spinal nerve ligation performed within 24 hours of delivery resulted in acute hypersensitivity that partially resolved over twothree weeks. Hypersensitivity returned temporarily following weaning.

“Understanding whether and how pregnancy or the puerperium protects against the development of posttraumatic chronic pain is important not only to women who give birth and their children, but may also provide therapeutic targets for future prevention and treatment of chronic pain in other populations,” write the authors of an accompanying editorial.

Full Text – Eisenach
Full Text – Gutierraz