Teen pregnancy rates are once again on the rise.  Michelle Gielan has that story and more in today's health watch report.  After a 10-year decline, the nation's teen pregnancy rate rose for the first time in 2006.  According to a new report, the overall teen pregnancy rate jumped 3 percent, with a four percent increase in the rate of births and a one percent increase in the rate of abortions.  Some researchers blame the increase on sex-education programs that focus only on encouraging abstinence and not on contraceptive use.  If you have high blood pressure AND are overweight, a low-carb diet may be your best bet.  New research found a low carb diet was just as good at helping people lose weight as the weight loss drug Orlistat.  But people who cut back on carbs saw their blood pressure improve more than those taking the medication.  There's more evidence that exercise can do your body...and your brain good.  One new study found that women who were more physically active during middle age lowered their risk for chronic diseases and heart trouble later in life.  Another report found moderate or high intensity exercise reduced the risk of cognitive impairment in men and women over the age of 55.  Those are some of today's top medical stories.  I'm Michelle Gielan - CBS News - New York.