FeministX has done a couple of interesting analyses of the relationship between employment and fertility. Her approach is macrolevel: she estimates the correlation across 23 countries, and over time in the U.S. The problem is that, more often than not, you use macrolevel data when you don't have relevant individual-level data available. With microlevel data, you can avoid the problems of small samples, country differences in data collection, and the danger of making the ecological fallacy (e.g., claiming that it is working women, as opposed to homemakers, who are having all the kids when the data can't tell you that). Plus, you have to use whatever macrolevel measures that happen to be available, while with GSS data you can custom-design your age group, period, race, etc. The typical weakness of individual-level survey data is whether respondents can be trusted. Fortunately, a solid argument can be made that women in the GSS are accurate in their answers concerning work status and number of offspring.
To answer the question, does working lead to more children, it seems to me that we should look at women who are old enough to have shown their fertility tendencies but are not so old that their kids are grown and consequently have entered the workforce. How about 35 to 44? (Feel free to do your own data crunching if you prefer another approach). And let's look at only this decade so we observe recent behavior. Also--I suppose we want to look at married women since no one would want to see single motherhood encouraged. Here are the results:
Married women who work part-time or who keep house average significantly more offspring than those who work full-time.
I looked up the demographic literature, and the general story--whether from microlevel or macrolevel studies--is that working reduces fertility. The one expection I found was that after 1985 the relationship across OECD countries switched from a negative to a positive. Some demographers have explained it in terms of factors like wider availability of day care centers, flexible hours at work, maternity leave--basically more social support for working mothers. Other demographers point to the negative relationship in each of these countries over time (FemX shows the opposite in the U.S.) and use fancy models to explain away the positive cross-sectional correlation (I don't have time at the moment to figure them out). So the conventional wisdom of the discipline (most clearly seen in the microlevel research) is that working reduces fertility--and fertility also reduces work--but work and babies are becoming less incompatible as societies adjust to the new realities. FemX's point that more income can help a couple afford additional babies seems reasonable, but mom takes on a much heavier load, and not everyone is so industrious.
I agree with the reader who wrote that talented adults need to get the message that parents have little influence on their kids' personalities, and that this old idea that children have to be doted on 24/7 to turn out normal is bogus. Send the tots to day care. Hell, for all I know, they'll be fine at boading school.
Let me add, however, that there are other serious consequences of female employment to worry about. It has probably been the driving force behind the decline of the American family. Now that women are working outside the home, marriage is no longer an economic necessity--it's a choice. So women are waiting longer to get married, delaying children, having illegitimate kids, and walking away from their marriages. And men realize that now a woman can take care of herself, so he's freer to not marry the mother of his children, to divorce his wife, and to fail to support the kids. It seems pretty clear that, overall, the breadwinner model is superior.