What causes premature detachment of membranes?

The development of the fetus is a very important thing for women after pregnancy. Pregnant women need regular prenatal checkups to observe the development of the fetus. Premature detachment of membranes is a relatively common phenomenon. There are many reasons for premature detachment of membranes, which are generally caused by high blood pressure or chronic kidney disease in pregnant women. It can seriously threaten the life of the fetus and may reduce the survival rate of the fetus.

Causes of premature detachment of membranes

Vascular disease in pregnant women. Pregnant women suffering from pregnancy-induced hypertension syndrome, chronic hypertension, chronic kidney disease and other diseases can cause spasm and infarction of the basal decidual arterioles, resulting in ischemia and necrosis of distal capillaries, leading to rupture and bleeding. Blood flows between the decidua basalis and the placenta, forming a retroplacental hematoma, which in turn leads to placental detachment. The bleeding continues to increase, the area of ​​hematoma continues to expand, and the area of ​​placental detachment also expands accordingly. Vascular disease in pregnant women is the most important cause of placental abruption, accounting for about half of the incidence.

Abdominal injuries. Traumatic injuries such as impact to the abdomen of pregnant women may cause rupture and bleeding of the blood vessels of the decidua basalis, leading to placental abruption.

Premature rupture of membranes. Premature rupture of membranes and excessive flow of amniotic fluid can cause a sudden drop in uterine cavity pressure and a sudden reduction in uterine cavity volume, leading to dislocation and detachment between the uterine wall and the placenta, damage to small blood vessels, and bleeding, which is also one of the causes of placental abruption. Premature rupture of membranes is more likely to occur during sexual intercourse in late pregnancy or when suffering from vaginitis. During the birth of twins, after the first baby is delivered, or when a pregnant woman with excessive amniotic fluid has her membranes ruptured to release the amniotic fluid, the amniotic fluid flows out too quickly and placental abruption is likely to occur.

Increased uterine venous pressure. In the late pregnancy or during delivery, if the pregnant woman lies in the supine position for a long time, the huge uterus will compress the inferior vena cava, causing venous reflux obstruction, congestion of the pelvic and uterine veins, and continuous increase in venous pressure, which will cause excessive congestion and rupture of the decidual veins, leading to placental detachment.

Regardless of the cause of the rupture and bleeding of the decidua basalis blood vessels, blood can accumulate between the decidua basalis and the placenta, forming a retroplacental hematoma. As the bleeding continues to increase, the pressure in the hematoma cavity continues to increase, causing the placental tissue around the hematoma to continuously peel off from the uterine wall and bleed. If the hematoma reaches and breaks through the edge of the placenta, the blood in the hematoma will flow out of the body through the cervix and vagina from the edge of the placenta that has been broken open, which is called manifest abscission.

Because the blood can flow out of the body, the pressure in the hematoma cavity decreases, the hematoma area no longer expands, and the placenta no longer continues to detach. Therefore, the condition is often mild. If the retroplacental hematoma fails to reach and break through the edge of the placenta and the blood cannot flow out, it is called occult abruption.

In patients with occult abruption, the blood accumulation in the retroplacental hematoma cavity increases, and the intrauterine pressure increases, forcing the blood in the hematoma cavity to penetrate into the uterine myometrium, causing separation and degeneration of uterine muscle fibers, and the surface of the uterus appears purple-blue, which is medically called uteroplacental stroke. Another serious consequence of placental abruption is that the damaged decidual tissue releases a large amount of thromboplastin into the maternal blood circulation, causing coagulation dysfunction. The blood that flows out is watery and there are no blood clots. This is medically known as disseminated intravascular coagulation (DIC).

DIC can often lead to refractory massive bleeding in parturients, and often leads to their death. It can be seen that placental abruption is an obstetric complication with serious consequences and high mortality.

Placental abruption is the second pregnancy complication causing antepartum vaginal bleeding after placenta previa. Although both are prenatal vaginal bleeding, they have their own characteristics. Placenta previa is bleeding without abdominal pain. During examination, the abdominal wall is soft and non-tender. Vaginal bleeding from placental abruption is often accompanied by severe abdominal pain. When the placenta attached to the posterior wall of the uterus abruption occurs, it often manifests as low back pain or abdominal and back pain. During the examination, it was found that the uterus was hard like a board and tender, and as the bleeding increased, the retroplacental hematoma continued to grow and the fundus of the uterus gradually rose.

Therefore, for pregnant women suspected of placental abruption, as soon as they are admitted to the hospital, the doctor will draw a line on the fundus of the uterus on the pregnant woman's abdominal wall with a colored pen, and observe from time to time whether the fundus of the uterus exceeds the drawn line and how much it exceeds, in order to estimate the degree of retroplacental bleeding and the progression of the disease. Timely B-ultrasound examination can help with early diagnosis and treatment. Once placental abruption is confirmed, it should be treated promptly. Waiting and observing for too long can easily cause the placental detachment surface to continue to expand, and the retroplacental hematoma to continue to increase, leading to uterine stroke, making the condition more serious and complicated. Therefore, early diagnosis and timely treatment are the key to reducing losses and achieving better outcomes.