"Because Jesus, the twelve apostles, Paul, and the prominent leaders in the early church in Jerusalem were all men, the impression prevails that early Christianity was primarily a male affair. Not so. From earliest days women predominated." - Stark, TC, p122.
Stark suggests that if Paul sent personal greetings to fifteen women and eighteen men in his letter to the Christians in Rome, and we assume that sufficient "sex bias" (his words) existed so that men were more likely than women to hold position of leadership, then the ratio suggest a congregation that was most likely disproportionately female. Historians point out that it was often wives that penetrated the upper classes of society with message of the gospel first. And one sample of the senatorial class who lived between 283 and 423 showed that 50 percent of the men, but 85 percent of the women, were Christians.
Stark goes on, in my opinion, to do some poor exegetical work on 1 Corinthians regarding the prohibition of women to speak in the public assembly. That aside, I believe his best work (in sociology and history and not so much as a Bible expositor, pastor or theologian) on this topic is summarized well in his Conclusion to this chapter:
"The rise of Christianity depended upon women. In response to the special appeal that the faith had for women, the early church drew substantially more female than male converts, and this in a world where women were in short supply. Having an excess of women gave the church a remarkable advantage because it resulted in disproportionate Christian fertility and in a considerable number of secondary conversions." - p136.