Vasa previa happens when the placenta lies in the lower uterine segment and because the lower uterine segment is not capable of nourishing the placenta, the placenta grows to reach the upper segment of the uterus so that it can have nourishment. The placenta is not meant to grow larger, when it does, it will slip through the cervix.
The blood vessels in vasa previa support the cell membranes on the cervix; the condition of vasa previa promotes cervical dilatation. Fetus born with vasa previa cannot affect the physical and mental aspect of the baby.
The condition of vasa previa does not always promotes dilatation of the cervix. In most cases, the placenta just move upward of the uterine wall to get nourishment and eventually stays there. Yes vasa previa can go away by it self.
During the first trimester when ultra sound is performed, the placenta reveals to be low lying in the lower segment. This has nothing to worry bout, most low lying placenta move upward as the uterus expand and it gets back in to the correct position. The case would not always like this, the placenta at times when instead of moving up to its correct position, it grows larger thus a cervical dilatation happens.
The risk of having a vasa previa happens when a pregnant woman has the following condition:
• The placenta lies in the lower uterine segment or partially covers the cervix.
• Multiple pregnancies (twins)
• Abnormalities of placenta (bi lobe placenta, succenturiate lobe)
• A woman who is using Intra veinus fluid during pregnancy
• When a woman underwent a previous uterine surgery
• When a woman experience a painless bleeding any time during pregnancy
Any doubts whether you are experiencing vasa previa or not, it is best to consult a Doctor right away. Doppler ultrasound can diagnose the presence of vasa previa by measuring the velocity of blood flow.