By now the embryo is about a quarter of an inch long, and my wife, when she isn’t throwing up, is talking about something goofy called the crown/rump length. That’s the distance from top of the embryo’s skull to the midpoint between the tops of its buttocks. Why this is important, I’m not sure.

But from what I’ve read, Babu’s larynx is beginning to form; so are the liver, pancreas, lungs, and stomach. He/She/It currently has a heart but no brain. Sarah still has both, each in working condition, but her bladder is not. Every sneeze and cough is potential disaster. She’s started packing an extra pair of underwear. And now Sarah’s brain has stopped working, too.

Most studies show that a woman’s brain really does shrink by up to five percent during pregnancy. I don’t know much about neurology, but I know that normally, my wife can recite every line of When Harry Met Sally and reel off every outfit she wore on our first seven dates. Now she can’t remember anything. “What kind of things are you forgetting?” I asked.

She stared blankly. She couldn’t remember.

I decided to do a little research. A 2003 study of pregnant women in India published in the Journal of Reproductive Medicine proved that pregnancy causes a significant decrease in brain chemicals that help transmit messages between brain cells. The result was a loss of functional memory. Various other studies corroborated this theory.

Other smart people have suggested that the stereotype of a forgetful pregnant woman is just that: a stereotype. A 2000 Australian study found many pregnant women out-performed non-pregnant peers on some memory tests. John Thorp, an OB/GYN at the University of North Carolina, told WebMD in a 2003 article that patients were constantly telling him they didn’t think as clearly as they once did-but there was nothing biologically backing that claim. “I think what women experience is competition for their attention,” Thorp wrote. “Suddenly, they’ve got more going on.” And across the board, pregnant women rate their abilities as worse than they were before they got pregnant. In other words, the phenomenon has nothing to do with science, but rather perception.

Perception or not, I noticed Sarah was mixing up days and times, and was periodically talking nonsense. On more than one occasion I caught her babbling to herself when she thought no one was around. One morning she was supposed to meet a friend for breakfast. Sarah waited 30 minutes at the restaurant and came home. What happened, I asked?

After mumbling something incomprehensible in a language that sounded like a cross between and Canadian goose call and shtetl Yiddish, I asked her to repeat herself.

“I had the wrong day,” she said, irritated. “I was supposed to meet her on Sunday.” As she stumbled into our bedroom, almost drunkenly, and lay down for a nice long nap, I began to suspect that she hadn’t just shown up on the wrong day. She’d gone to the wrong restaurant too.