Most professionals agree that we need to explain puberty and sexual intercourse to our children. It may be to your advantage to explain it sooner rather than later before your children get the information from older siblings or siblings of friends. The more they learn before you have the opportunity to share information in an open and nurturing way, the more embarrassed they will be to talk about it with you.
By talking to them at an early age, you make it comfortable to talk about sex. They will be more likely to come to you if they have a question versus their friends or elsewhere. Studies have shown children that are educated on sex by their parents are less likely to become sexually active at a young age. If you can instill with them the purpose and special nature of sex, they will have a greater respect for it and for themselves and others. A great book to read to prepare you for this conversation is “The Sex Wise Parent” by Janet Rosenzweig.