But all of that is preventable, she added.

“It’s absolutely essential not to be complacent about what I call a ho-hum sex life. Touching is a very primal way of connecting and bonding,” Ms. Weiner-Davis said. “If those needs to connect physically are ignored over a period of time, or are downgraded so that it’s not satisfying, I can assure people there will be problems in the relationship moving forward.”

Slow down and start over.

If you had a vaginal birth, you and your partner may expect to begin having sex as early as six weeks after the baby is born, if you have been physically cleared to do so.

[Read our guide to sex during your pregnancy.]

For some couples, that signals “the clock is now ticking,” said Emily Nagoski, author of “Come As You Are: The Surprising New Science That Will Transform Your Sex Life.”

But a lot of women simply won’t be ready that early. And that’s O.K.

“After the postpartum checkup, I didn’t feel like myself, I didn’t feel physically ready to have sex,” said Emily Stroia, 33, who lives in Los Angeles. “In terms of libido, I didn’t really have one.”

Ms. Stroia, the mother of a 10-month-old, eventually starting having sex with her partner once a month — but before she became pregnant, they had sex nearly every week, she said.

“I still kind of forget that I’m in a relationship,” said Ms. Stroia, who is struggling with sleep deprivation. “I have to remind myself that I have a partner.”

After any potential medical problems are ruled out, Dr. Nagoski advises couples to “start over” with one another by establishing a sexual connection in much in the same way they might have done when they were first getting to know each other: making out, holding each other and gradually moving in the direction of bare skin.