Placenta previa

Japanese: 前置胎盤 - ぜんちたいばん（英語表記）Placenta previa

What is the disease?

This refers to a condition in which the placenta is attached to the lower part of the uterus and part of it extends to the internal cervical os. Depending on the extent to which it extends to the internal cervical os, it is called total placenta previa, partial placenta previa, Periphery ( Henen ) There are three types of placenta previa (Figure 16).

How symptoms manifest

During the latter half of pregnancy, as the lower part of the uterus stretches and the cervix dilates, part of the placenta Peeling ( Peeling ) This occurs around the 30th week of pregnancy as painless bleeding that usually disappears naturally. This is called warning bleeding.

During childbirth, uterine contractions Placental abruption ( Taiwanese ) The lower part of the uterus is prone to heavy bleeding. Decidua formation ( Lazy and silly ) (The endometrium changes into the decidua due to pregnancy) Scarcity ( Tobo ) Because of this, the placenta is prone to adhere, which can lead to severe bleeding that can be life-threatening for the mother. Curettage ( Yes. ) It is common among people with a history of ovarian cancer, and is thought to occur when deformation of the uterine cavity and abnormalities in the lining of the uterus occur, causing a fertilized egg to implant in the lower part of the uterus.

Testing and diagnosis

Clinical symptoms are important, and if painless genital bleeding occurs in the second half of pregnancy, this disease is suspected and examined. Inserting a finger into the cervix during a pelvic examination may cause heavy bleeding. Ultrasound tomography is used to make a definitive diagnosis, depicting the placenta covering the internal cervical os. Transvaginal ultrasound examination is extremely effective for observing the area around the internal cervical os.

What appears to be placenta previa during the middle of pregnancy may move away from the internal cervical os as the pregnancy progresses, so if this disease is suspected, regular observation is required.

Treatment methods

Since bed rest is important in the management of this condition, it is common for women to be hospitalized around the 28th week of pregnancy, regardless of whether they are bleeding or not. If bleeding is accompanied by uterine contractions, a tocolytic drug is used. If the amount of bleeding exceeds 500 ml, delivery of the fetus and placenta by Caesarean section is considered.

Shiro Uezuma

Figure 16. Types of placenta previa
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Figure 16. Types of placenta previa

Source: Houken “Sixth Edition Family Medicine Encyclopedia” Information about the Sixth Edition Family Medicine Encyclopedia

Japanese:

どんな病気か

　胎盤が子宮下部に付着し、その一部が内子宮口に及ぶものをいいます。内子宮口にかかる程度により、全前置胎盤、一部前置胎盤、辺縁(へんえん)前置胎盤の3種類に分類されます（図16）。

症状の現れ方

　妊娠後半期の子宮下部の伸展や子宮口の開大に伴い、胎盤の一部が剥離(はくり)し出血します。妊娠30週前後に無痛性の出血として起こり、自然に消失することが多いようです。これは警告出血と呼ばれます。

　分娩時には子宮収縮に伴い胎盤剥離(たいばんはくり)が進行し出血多量になりやすくなります。子宮下部は脱落膜形成(だつらくまくけいせい)（子宮内膜が妊娠の影響を受けて脱落膜へと変化すること）に乏(とぼ)しいため、癒着(ゆちゃく)胎盤となりやすく、その場合には母体の生命に関わる大出血となることがあります。多産婦、前回が帝王切開であった人、子宮内膜掻爬(そうは)の既往がある人などに多く、それにより子宮内腔の変形や子宮体部内膜の異常が生じ、受精卵が子宮下部に着床するため発生すると考えられます。