My baby girl is 5 months old. She can sit when put in a sitting position, but when you want her to stand up and hold her, she’ll use one leg and cry. She hasn’t put weight on her legs yet and when you put her on her stomach, she cries but when she is lying, she kicks with her legs and recognizes people and even cries for them. What could be the problem?
Since your baby is only 5 months old, I don’t necessarily think that anything you mentioned would definitely indicate a problem, but if you are concerned about her legs please do consult your baby’s doctor. Many babies do not begin to bear weight on their feet when held in a standing position until they are between 6-9 months old. It is great that your daughter is able to sit when placed in a sitting position. Since you mentioned that your daughter will only place one leg down when held in a standing position and will cry, you can ask your doctor to check her hips to make sure she has no problems with her hips being out of place. It is good that she will kick both legs when she is lying on her back. One thing I would encourage for your baby is more time on her stomach (we call it “tummy time”), since this is the most important position for her to be in during waking hours in order to strengthen her muscles that she needs for the development of important motor milestones such as rolling, independent sitting, crawling and later walking.
You can gradually ease her into more time on her stomach, by playing with her as she lies on your chest facing you or getting down on the floor on a blanket with her. Try to build up her ability to play in this position for at least 5-10 minutes, 3-5 times per day. You can read a few of our articles on our website which tell you why tummy time is so important for young babies. And also check what is typical for her motor milestone development. Right now at age 5 months you want to focus more on the tummy time, rolling actively in both directions (stomach to back and back to stomach), as well as reaching for toys when she is on her stomach by being able to hold her chest up, pushing up on extended arms and reaching for a toy with one hand or the other. Here is an excellent source of information on how to encourage tummy time during play, carrying, diapering, etc.