I tried to remain calm. I was already overweight when I became pregnant, and I was terrified of what the books said that predisposed me to: gestational diabetes, preeclampsia, high blood pressure — the list goes on. I had worked hard to eat well and exercise often and was perversely proud that I hadn't gained much weight. A pound here. Two pounds there. But 10 pounds? That was too many pounds.

The nurse led me into an exam room and took my blood pressure, the cuff squeezing so tightly, it left a mark.

"That can't be right," she said, letting the cuff deflate all the way. She tightened it again, waited, and then tried to not look alarmed.

"180/110," she said softly, hurrying the cuff into a loop. She reached for the door. "I have to see what the doctor wants to do," she said, and then she was gone.

Two months later, at my first postpartum appointment, that same nurse would lead me into that same exam room and take my blood pressure again.

"120/78," she said. She draped the blood pressure cuff over the machine and started to leave. Then she stopped. "I heard what happened to you." She shook her head. "That must have been so scary."

At birth, humans are the fattest species in the world. A full-term baby can be born with up to 15% body fat. It's not entirely clear why we need this much fat when we are born, but some speculate it's a way for babies to store energy for the days between when they are born and when their mother's milk comes in. It's pretty simple evolutionary math: A fat baby is one that is more likely to survive.