(HealthDay News) -- Many women are eager to slim down after baby arrives, but it takes time for your body to recover.

MONDAY, Jan. 14 (HealthDay News) -- Heavy smokers are more likely to develop aggressive and deadly bladder cancers than those who smoke less or nonsmokers, new research shows.

MONDAY, Jan. 14 (HealthDay News) -- Giving the diphtheria, tetanus and pertussis (DTaP) vaccine in the thigh rather than the arm reduces a toddler's risk of an injection-site reaction that requires medical attention, according to a new study.

MONDAY, Jan. 14 (HealthDay News) -- Colic is a common problem for babies, and new research may finally provide clues to its cause: A small study found that infants with colic seemed to develop certain intestinal bacteria later than those without the condition.

MONDAY, Jan. 14 (HealthDay News) -- Using Twitter may help people lose weight by providing them with social support, researchers report.

MONDAY, Jan. 14 (HealthDay News) -- After New York City made the streets near some of its schools safer, the number of children struck by cars each year dropped substantially, a new study shows.

MONDAY, Jan. 14 (HealthDay News) -- Nearly a third of American teenage girls say that at some point they've met up with people with whom their only prior contact was online, new research reveals.

Here are some of the latest health and medical news developments, compiled by the editors of HealthDay:

MONDAY, Jan. 14 (HealthDay News) -- Kids who eat fast food three or more times a week are likely to have more severe allergic reactions, a large new international study suggests.