I had it all planned out: I parked the car, turned off the wipers and lights, put the keys in my purse, gathered the diaper bag and other belongings in preparation for the next steps — getting out of the car, walking around it, putting the baby bags and purse down in such a way that they could be picked up with one hand after I had opened the back seat door, unbuckled and lifted my newborn from his car seat, then locked the car and moved toward my mother’s house, all the while making reassuring sounds for his benefit.

It seemed to require the advance planning of a military movement, but I felt I was doing OK with this manoeuvre until I was dismayed to find I couldn’t open my own door to begin it. Something’s wrong with the car — we’re trapped, I reasoned in panic.

Then, with sense of utter stupidity, I realized that I had unconsciously locked the car doors while still sitting in the driver’s seat thinking of everything I had to do in advance once I’d opened the door. “I have lost what little brain I carried into this pregnancy,” I wailed internally.

Well, yes and no, says Lynne McLeod, an obstetrician/gynecologist at the IWK Health Centre in Halifax.

“ This is a common concern among new moms and their partners,” says McLeod. “In fact, I took a quick, unscientific poll here at the hospital among obstetricians, new moms, family doctors, residents just returning to work after having a baby and nurses with older children, and 100 percent of these people had experienced a memory loss or the loss of cognitive ability during and immediately after pregnancy. Everyone knew what I was talking about.”

But why? No one seems to know for sure.

“ A few scientific studies have tried to link hormonal changes to memory loss, but nothing has been conclusive,” says McLeod. “However, one study with three sets of women — not pregnant, pregnant and postpartum — does show a significant memory deficit in women around the time of delivery. So something does change which impairs a new mother’s ability to remember. We just can’t show what that change might be. It doesn’t appear to be hormonal.”

What’s left is a number of hypotheses around why pregnant women and new mothers feel just plain dumb.

After a new baby, says McLeod, and even during pregnancy, women can be physically and emotionally exhausted. Even when nothing’s going wrong, it’s still an overwhelming and demanding time, and that can affect how people reason and think. “With a difficult pregnancy or a bad birth experience, the change in your ability to think and act can be even more pronounced,” she says.

Another explanation? Simple overload. “After any birth, there’s so much to focus on — is the baby eating, is she sleeping, is she gaining weight? Couple this with a lack of sleep, and the brain no longer prioritizes short-term memory,” says Macleod. “You don’t need to remember your mother’s phone number, but you do need to think about whether the baby is dressed warmly enough.”

The stress of being a caregiver can cause problems with attention and memory over a period of time, notes Marilyn Smith, a psychology professor at the University of Toronto. “I’m doing a study on the effects of being a family caregiver of a dying patient,” she says. “I’m seeing that the caregiver’s memory problems can persist as long as six months after the stress is relieved.”

The good news for most mothers is that it won’t last. “It most definitely is short-term,” says McLeod. “Your memory will come back. You will regain your IQ of 700. The important thing is not to worry and enjoy your baby.”

As well, she says, avoid isolation. It can exaggerate memory loss. “If you’re not exercising your brain among adults, at least for some of the time,” says McLeod, “you can feel you’re losing it.”

Mother Nature knows what’s important, she adds. “The memory loss is partly a coping mechanism to make sure you’re prioritizing properly. Think of it as being good for the baby.”

Catch You Later: Memory Loss at Menopause

Many women going through menopause experience the same kind of forgetfulness that new mothers do and despair, assuming mental decline has begun. The good news: It hasn’t. The September issue of the American journal Neurology reported that a study of more than 800 menopausal women over two years showed that if they’re forgetful sometimes, it’s more likely because they are busy, distracted and stressed-out with middle-age pressures: teenage children, elderly parents and career demands.

The researchers found no proof that hormonal changes in menopause cause forgetfulness. It may be that the brain does not need the hormones as much as we think.