Reintroduced populations of threatened species are often founded by a small number of individuals, but maximising genetic diversity is often a criterion for founder selection. Reintroduction of pregnant females has been proposed as a means of maximising productivity and genetic diversity, but it is unclear whether the release of pregnant females increases the effective number of founders. Ten male and 20 gravid female egg-laying skinks (Oligosoma suteri) were reintroduced to Korapuki Island from Green Island, New Zealand in 1992. We sampled the populations on both Green and Korapuki Islands to examine the effect of reintroduction on the genetic structure and fitness of egg-laying skinks following release. The population on Korapuki Island showed multiple genetic signatures of a bottleneck that were not detected in the population on Green Island. At the individual level, juveniles on Korapuki Island were more homozygous than adults on Korapuki and Green Islands. However, we did not find evidence of inbreeding depression using two performance-based surrogates of fitness. Further, the population on Korapuki Island had a significantly larger effective population size than would have been expected by reintroduction of 30 skinks, based on 10,000 simulated populations. The reintroduction of gravid females aided in increasing the effective number of founders, and may be a viable option for maximizing genetic diversity in reintroduced populations, particularly for long-lived species. However, the continued loss of genetic variation in reintroduced populations may have more insidious long-term consequences, such as the loss of adaptive potential, which cannot be assessed in the short-term.