Growth hormone treatment after cesarean delivery in rats increases the strength of the uterine scar

OBJECTIVE: We sought to determine whether postcesarean treatment of rats with growth hormone (GH) affected the strength of the uterine incision in the puerperium and in a subsequent pregnancy. STUDY DESIGN: Forty-eight near-term pregnant rats were delivered by cesarean section, Half received subcutaneous recombinant human GH (2.0 mg·kg^-1·d^-1) for 7 days; control animals received saline injections. Four weeks after delivery, the uterine bursting pressure was determined in 5 treated and 5 control animals. Eight rats in each group were used to study uterine hydroxyproline concentrations and the histologic characteristics of the scar. Twenty-two animals were rebred 30 to 40 days after their cesarean sections. After repeat cesarean delivery, on day 19, the bursting pressure and hydroxyproline concentrations of the previous hysterotomy scar were determined. RESULTS: The uterine horn bursting pressure in the GH-treated animals was significantly greater than that in the control animals both 28 days postpartum and near term in a subsequent pregnancy. The uterine hydroxyproline concentrations followed the same pattern. Histologic study of the scars showed they were thicker and had less cellularity in the treated animals than in the control animals. CONCLUSION: Postcesarean treatment with GH increased the bursting strength of rat uterine incisions. This effect was accompanied by a significant increase in collagen content and persisted through a subsequent pregnancy.