Thank you for being such concerned. It is trully important that they are tightened after birth for may reasons which i will assume you know. The following may help.
Usually during the process of child birth they stretch due to the forces of the baby's body parts, e.g , the head and some times you get a slit. One of the characteristics of muscles adaptations. If the muscle is kept in a particular lenghth for long, it tends to adapt to the conditions behind that length by changing structurally.
For this reason after deliver you need to ensue that atleast most of the time you need to sit with your legs so close to each other.
However, for all this to be a success you will need to ensure proper vaginal hygiene to ensure that the vaginal injuries resolve quickly. ensure that you take your antibiotics as prescribed.
You may neeed to avoid sex for some considerable time, say 3months. sex encourages stretch.
Do not get used to the idea of washing down with warm water. warm water reluxes muscles. you may use only for very few days after delivery.
Always perform what is called pelvic floor exercise-voluntarily and always tighten the muscles around the vagina for as long as you remember and for as long as you can afford.
Just avoid postures that keep your legs apart.
With that my dear i hope i have tried to answer you.
pliz let me know if got my answer.