K.P.
Although you need to be outside a lot, you are probably going to have to buckle down and give your son a consequence when he runs out in the street. My children are not allowed in the street either, even though their friends ride their bikes right down the middle of it. I think, were I you, the next time he ran out in the street I would take him by the hand and take him right back inside to sit in timeout for 2 minutes. When timeout is over, get down on his level(as much as you can for being pregnant)look him straight in the eyes and tell him, "if you go in the street, you come inside to sit." "It is dangerous to go in the street without holding mommy's hand." Be consistent!! Do this each time he goes to the street. He will soon learn it is not a game you will play with him, and eventually he will stop. I did this with mine, and they are now 6 and 3, and never cross the street without asking, and never chase a ball that has gone in the street. It is just something we had to train them to do to keep them safe.