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Your Developing Baby, Week by Week

Your baby begins as a tiny cluster of cells, but during the nine-month process of pregnancy she becomes an amazing baby with facial features, a beating heart and kicking legs. Find out what's happening with baby's development week by week.
week 39 Week 39

By now your baby has likely reached his birth weight (typically between 6 and 9 pounds) and length (18 to 22 inches from head to toe). He's accumulated enough body fat to stay cozy after he's born, and your placenta continues to supply him with nutrients and antibodies that will help fend off illnesses. If you could sneak a peek at your baby's final moments before birth, you'd see that his head is down toward your pelvis (if he's not in the bottom-down or breech presentation, in which case your healthcare provider might suggest a cesarean section). Your baby's body will either be straight up and down, called longitudinal, or positioned at an angle, called oblique. Along with spying your baby's body position, if you could see his head, you'd notice that he's head-down and facing your spine, which is the most common position (called anterior presentation). But sometimes, babies present head-down but facing toward your abdomen. This is called occiput or cephalic posterior. Your baby might lean slightly to one side or the other, meaning that he is either "right" or "left" anterior, or "right" or "left" posterior.