In my personal, non-binding opinion, it's fine and even desirable for women to work until the first child comes along. A few points however:
1. If she's just working at Wal-mart, target, or as a cashier, might as well not bother. You won't be socking away any money -- she might be spending as much or MORE than she's making, on clothes, makeup, extra car, gas, fast food, co-worker gift exchanges, extra money spent keeping up with co-workers, etc. (My wife was working as a professional -- an accountant, albeit a lower-paid one -- so we cleared #1)
Also don't forget the OPPORTUNITY COST of having your wife work. If she's working for "the man", she can't be cleaning, cooking, helping you save money, making clothes, calling businesses and researching stuff for you, helping you with bookkeeping, planning garage sales, SHOPPING garage sales, grocery shopping, you name it. If she works outside the home, you're on the hook for ALL that stuff. I guess what I'm saying is, not all women eat bon-bons and watch soap operas if they don't work outside the home. Some are industrious.
2. You do want to make sure your wife isn't going to get tempted by all the men she will spend 8 hours a day with (way more than she spends with you). A good reason to bring her back home full-time during the newlywed phase of your marriage...
3. You must NOT, under any circumstances, grow to depend on the wife's income! You must be ready to drop that income as soon as the first baby is born. I repeat, you must learn to live with a budget on ONLY the husband's income. All "her" income must be treated as a temporary windfall/bonus, and should go towards paying off debt, saving for a house, paying off your (first) mortgage, paying off student loan debt(s), building savings, etc.
4. It's desirable for the wife to help you "get ahead" as it were, given the modern economy. It's SO difficult for young couples to get started compared to generations past. As great as it would be for your wife to greet you with a warm meal and a massage when you get home -- it would be better to use that first year to save up and get a running head start on REAL married life, which requires a lot of resources. You can't fit 10 kids in a 1400 square foot starter home! And did I mention that braces are about $5500 per kid?