As much as possible, it’s helpful for parents to work as a team on the birds and the bees (and everything else). Kids benefit from knowing the views of both parents and from being able to ask questions of whomever happens to be around at the moment.

I know, that’s not the way it goes down in most families. Sometimes the mother takes the lead on puberty and sex-ed with daughters and the father with the sons. Often, mothers do the bulk of sex ed with kids of any gender. (I’m not sure why that is. Maybe mothers are around more, or maybe they seem more approachable?)

However the talking gets divided, wise parents keep each other informed about what kids are asking and what they’ve been told. That helps you prepare for future conversations and, if necessary, discuss how to handle trickier topics. You may not completely agree, but at least you’re on the same page.

Young kids are usually oblivious to the fact that parents compare notes. Before puberty approaches, kids don’t have much emotional energy around sexual topics; they’re just facts about how the world works.

By late elementary school or certainly middle school, kids start to become modest. As they become aware not only that bodies mature but that their personal body will change, they feel self-conscious. That may trigger the first reason for “please don’t tell”: embarrassment.

So your daughter may say “Please don’t tell Dad” when you buy her first bra or she gets her period. It’s obvious to Dad that his baby girl has been developing; the two of you have talked about it. How can you not mention her milestone? Or your son may ask you embarrassing questions about pubic hair or erections and ask you not to tell Mom.

Strike a balance between respecting privacy and keeping the other parent in the loop. Acknowledge the awkwardness, give your child some time, and be honest that you will tell, soon. “It’s embarrassing to think about Dad knowing how your body is changing. I remember it was awkward for me with my father. But Dad loves you, and he’s noticed you’re growing up. And he knows all about periods because I have them and his sisters did. So I don’t feel right not telling him. Would it help if I wait a few days? Or maybe we could leave the box of pads where he’ll see it, and then he’ll know without anyone having to say anything? What would make it work best for you?”

You’re not obligated to keep her development a secret from her other parent even if she wants you to. But to keep her trust, don’t lie. Far better to have a convo about why you want to tell than to have her feel you betrayed her.

The other “please don’t tell” scenario is behavioral rather than developmental. This is when your kid has done something, or plans to do something, and doesn’t want the other parent to know. Maybe you found a box of condoms in his room, or she asked to be put on birth control, or you walked in your teen and their sweetie at an awkward moment. What then?

Several factors might influence your next move:

• How you found out about the situation. Did you happen to see or hear something, or did you child come to you in confidence? If he came to you for help or advice, you’d be more likely to protect his privacy.
• Why your child doesn’t want the other parent to know. Because if the two of you work together, she’s less likely to get what she wants? Because one parent is volatile, even violent, and he’s scared? Because she knows you’re easier to talk to—or easier to manipulate?
• The seriousness of the situation. If your kid asks you to not tell something that’s emotional (like a crush) or just embarrassing, respect his privacy. If it’s something with real risks, like sex, you might be more likely to tell—especially if your kid is relatively young or is behaving irresponsibly (e.g., not using birth control and condoms).
• The effect not telling would have on your relationship with the other parent. If the information is important and you don’t share it, that could undermine the trust between you. The other parent might be less inclined to share important information with you in the future. You have to balance parent dynamics with keeping communication open with your child. In most situations, more transparency is better.
• Whether you need guidance. If you’re confused about how to handle a situation, that might make you more likely to talk to the other parent. “This is complicated. I have mixed feelings about it, and I need to think about how to proceed. Your Dad’s input on this will be important to me.”

Whether or not you decide to tell the other parent, be honest with your kid about your plan. Promising to keep a confidence and then spilling it undermines trust; she’ll be much less likely to turn to you in the future. It’s much better to tell the truth upfront: “This is important, and Mom and I are a team. She’ll want to know about it. Shall I talk to her, or will you?”