If a mother tells her children that they will be having a baby shortly, b’ezras Hashem (with G-d’s help), she has a golden opportunity to educate them to the tznius of not revealing secrets. She should tell her children that she is telling them the good news so that they can look forward to a simcha. At the same time she should add that this is the business of no-one outside their family. They should therefore not talk about it in school nor tell even their closest friends until after the birth. In this way, the children will grow up knowing that a person must be discreet and not divulge secrets that he or she is told. [Note: Some have the custom not to tell young children anything about an expected simcha until the birth has actually taken place. Also, even those who do tell must know that children of six and under are usually unable to keep a secret. Such young children should therefore not be told things that are not to be spoken about.]

With such a chinuch, a girl will know that there are things, such as physical changes when growing up, that a mother explains to her daughter which must not be discussed at all — not even with her closest friends.

Children educated to keep secrets do not become secretive
It should be noted that educating children not to reveal secrets does not mean the children are being brought up to secretive and not talk freely about things that are not secret. In fact Esther, who is pointed out by our Sages as being a tznua (modest) and a person who kept secrets, is the very person about who our Sages say, כל האומר דבר בשם אומרו מביא גאולה לעולם — “Whoever attributes words of wisdom to the one who actually said them — rather than take the credit themselves — brings redemption to the world.” ¹ This is learned from the fact that Esther disclosed to Achashveirosh the plot of Bigson and Seresh in Mordechai’s name, and did not suppress the true source of the information. ² This in turn brought about the salvation of the Jewish people. From here we see that Esther spoke freely when it was right to speak. She even revealed things that others might not have revealed. However, when something was not to be revealed, she was a master of self-control in speech and did not reveal it.