THE indiscriminate worries and ruminations that churn through the mind of Cheryl Downs McCoy are matters most working mothers have rifled through at some point: “I need to call that guy about fixing the car. I think I’ve run out my daughter’s favorite snack. Should I change the batteries in the smoke alarm?”

These are entirely acceptable matters to ponder. But not at 3 in the morning. Yet that is when Ms. McCoy, a 45-year-old museum exhibit writer in Oakland, Calif., lies awake, debating and categorizing the details of working motherhood.

“Most of the time I get stuck mulling over the logistics of how everything’s going to get done - my brain really digs down the minutiae,” said Ms. McCoy, who has consulted a sleep therapist and has tried every prescription and over-the-counter soporific, from Ambien to low-dose anti-depressants, to assuage her maternal unrest.

For some women, the drug of choice is Lunesta; for others, melatonin. Ms. McCoy knows a mother of two who takes Xanax a few times a week, “but she worries about addiction so some nights she just doesn’t sleep at all rather than take it,” she said. “I think she saw the irony in not sleeping because she was anxious about taking an anti-anxiety medicine in order to sleep.”

Mother’s little helper of the new millennium may in fact be the sleeping pill - a prescription not likely to inspire a jaunty pop song anytime soon. Nearly 3 in 10 American women fess up to using some kind of sleep aid at least a few nights a week, according to “Women and Sleep,” a 2007 study by the National Sleep Foundation, a nonprofit research group.

Take, for example, Chris Baldwin, a 43-year-old mother of two. Ms. Baldwin goes through extended jags of Tylenol PM only to cut herself off after a fortnight to avert dependency. “The mornings after I stop, I get a hangover,” she said ruefully.

One of the cruel jokes of motherhood is that the sleeplessness of pregnancy, followed by the sleeplessness generated by an infant (a period in which a staggering - truly - 84 percent of women experience insomnia), is not followed by a makeup period of rest. It is merely the setup for what can become a permanent modus operandi.

Sleep-medicine practices are overwhelmingly dominated by female patients. Dr. Nancy Collop, director of the Emory Sleep Center in Atlanta, said three out of four insomnia patients at the clinic are women.

Why all the angst over bedtime, the one part of the day that, barring nightmares, ought to bring deeply needed peace? Many believe that sleep deprivation among women has worsened. In the “Women and Sleep” study, 80 percent of women reported being just too stressed or worried to turn out the proverbial lights.

Dr. Collop points to the persistent creep of technology into the after-hours, a time once reserved for physical and psychological winding down.

“There’s always the worry another e-mail has come in,” she said. “Just the light from the electronic book or the iPad screen is stimulating.”

It is hard to stop yourself from taking one last just-before-bedtime peek at the screen before calling it a day. For many, that makes falling asleep in the first place a problem.

“My brain is just going, going, going,” said Erica Zidel, a mother and a founder of a baby-sitting company in Boston, who takes melatonin to fall asleep. “It’s so active that I can’t slow it down.”

While women with infants are loath to take something that might conk them into an oblivion the sleep monitor cannot penetrate, mothers with older children seem to have fewer misgivings.