Programmed cell death during development resulting from the lack of appropriate survival factors has been demonstrated in both neurons and oligodendrocytes and occurs mostly in the form of apoptosis. We now demonstrate that Schwann cells in the rat sciatic nerve undergo apoptosis during early postnatal development and that the amount of apoptosis is markedly increased by axotomy. The apoptotic Schwann cells express the low-affinity nerve growth factor receptor but not myelin-related proteins, indicating that they are in the premyelinating state. Apoptosis resulting from normal development or from axotomy can be inhibited markedly by exogenous neuregulin. Consistent with this, the neuregulin receptor components erbB2 and erbB3 are expressed and phosphorylated in developing sciatic nerve. These data suggest that Schwann cell number in developing peripheral nerve is regulated by apoptosis through competition for axonally derived neuregulin.

OBJECTIVE To estimate whether 6-month use of the levonorgestrel-releasing intrauterine device (IUD) would be higher when insertion occurred within 10 minutes of placental delivery compared with 6–8 weeks postpartum. METHODS We enrolled pregnant women planning vaginal deliveries and desiring a postpartum levonorgestrel-releasing IUD. Patients were randomly assigned when admitted in labor to postplacental or delayed IUD insertion. The women followed up in person at 6–8 weeks and 6 months and were contacted by telephone at 3 months. Women were ineligible for a study IUD postenrollment for intrapartum events including infection, hemorrhage, and cesarean delivery; these women were contacted by phone at 3 and 6 months. Expelled IUDs were replaced per patient preference. RESULTS Successful IUD placement occurred in 50 of 51 participants (98.0%) and 46 of 51 participants (90.2%) in the postplacental and delayed groups, respectively (P=.2). Expulsion within 6 months occurred in 12 of 50 (24.0%; 95% confidence interval [CI], 13.1–38.2) and two of 46 (4.4%; 95% CI 0.5–14.8) participants, respectively (P=.008). Intrauterine device use at 6 months was 43 of 51 (84.3%; 95% CI 71.4–93.0) and 39 of 51 (76.5%; 95% CI 62.5–87.2), respectively (P=.32). For ineligible patients, only 11 of 41 (26.8%) women were using IUDs at 6 months and two (4.9%) had become pregnant. CONCLUSION Intrauterine device use 6 months after delivery is similar in women who have postpartum or scheduled delayed IUD placement through a study after replacement of expelled IUDs. Expulsions are significantly higher with postplacental compared with delayed IUD placement. Women asked to follow up with their own health care providers for delayed insertion are significantly less likely to receive an IUD. CLINICALTRIALREGISTRATION ClinicalTrials.gov, www.clinicaltrials.gov, NCT00476021. LEVEL OF EVIDENCE I