Astro.com is a great resource for charts, and it's worthwhile to get an account there, also.
When you have the charts, check your fifth house for any planets. The planets Saturn, Mars, and Pluto are not auspicious for pregnancy. The planet Mercury has traditionally symbolized children, so check him out, too.
If your chart looks positive, check your husband's chart for anything in his fifth or any bad aspects to his Mars. If his chart also looks "potent" (heehee), cast a synastry chart and look for any rough aspects between your Mercury-s and Saturn-s.
Best of luck to both of you, and please post your charts when you cast them!