The placenta is an important material medium for the mother to nurture her baby, and placental abnormalities are a relatively common condition during pregnancy. There are many types of placental abnormalities, some of which are even unheard of. However, since the placenta plays an important role in material exchange between mother and child, the placental abnormality particularly requires the attention of pregnant women.
Placenta as an important organ for material exchange between the fetus and the mother has the following two main functions. (1) Material exchange: the placenta transports approximately 50% of the oxygen inhaled and approximately 30% of the glucose ingested to the fetus, while removing CO2 and metabolic waste produced by the fetus; (2) secretion of hormones, including the human chorionic gonadotropin (HCG), human placental lactogen, cell factors, growth hormone, insulin-like growth factors, corticotropin releasing hormone and pro-angiogenic factors, such as vascular endothelial growth (VEGF) and placental growth factor (PIGF), to maintain the normal pregnancy process. In addition, it plays a defensive role to ward off the invasion of bacteria, pathogens and drugs.
The placenta is actually a piece of round, thin-edged flesh with a vascularized surface, 15-20cm in diameter and 2-4cm in thickness. The placenta starts developing at about 7 weeks of gestation, and it is fully formed after 12 weeks of gestation, basically mature after 30 weeks of gestation, and in a fully mature state at about the 38 weeks of gestation. As the placenta develops to maturity, its function becomes more complete.
B Ultrasound Examination is a Main Way to Check the Condition of Placenta
Generally, the best time to diagnose whether there are any placental abnormalities is before 28 weeks of gestation for a singleton and 20 weeks of gestation for a twin. Placental abnormalities that are detected too early or too late may not be easily detected because the placenta is not sufficiently clear, not yet formed, or obscured. Moreover, this is also the time for the "birth defects test", so it is recommended that the mother walk around a lot before entering the B ultrasound room and take some food to make the baby "excited" to ensure a smooth examination.
B ultrasound is the first choice to check for placental abnormalities, but due to imaging limitations such as field of view and contrast, the doctor may also require the mother undergo a magnetic resonance imaging (MRI) for further confirmation if necessary. Please rest assured that MRI is a non-invasive, radiation-free test with higher clarity compared to B ultrasound. If necessary, it is also necessary to follow the doctor’s instructions to complete the examination.
Placenta Previa and Placental Abruption are the Most Common Placental Abnormalities
Placental abnormalities are mainly divided into abnormalities of placental morphology and abnormalities of placental position. The two placental abnormalities we describe below are both abnormalities of placental position.
Placenta Previa - Inferior Edge of Placenta is Infinitely Close to the Internal Cervix Uterus
Normally, the placenta attaches to the posterior, anterior or lateral wall of the uterus. During the whole pregnancy, the inferior edge of the placenta should not be less than 2cm from the internal cervix uterus. The diagnosis of low-lying placenta is made once the inferior edge of the placenta is 0-2cm from the cervix uterus after 28 weeks of gestation, and if the inferior edge of the placenta reaches or covers the cervix uterus, which is "infinitely close" to 0, then the diagnosis of placenta previa is made.
The most significant danger of a placenta previa is bleeding, and the risk of bleeding is greatly increased during pregnancy, during labor, and after delivery in case of the placenta previa, which in turn will lead to anemia in the pregnant woman and even shock, and the fetus will suffer intrauterine distress, severe hypoxia, or intrauterine death. Therefore, when placenta previa is detected, you must follow the doctor’s advice to go home to bed rest or hospitalize for further treatment, and avoid activities that increase abdominal pressure such as straining to defecate, frequent coughing and squatting.
Placental Abruption - the Placenta Is Already Removed before the Fetus is Delivered
Under normal circumstances, the placenta is tightly attached to the uterine wall, and only when the fetus is completely delivered in the third stage of labor, the placenta completes its mission and is removed. The condition in which the placenta is partially or completely removed from the uterine wall before this period, that is, before the fetus is delivered, would be called placental abruption.
The placenta is an important hub for the fetus to get nutrients in the uterus, if 2/3 of the placenta or more leaves its "post of duty" early, the fetus will die due to severe depletion of oxygen, and the pregnant woman will suffer massive hemorrhage, if necessary, it even needs to remove the uterus to save her life, so it is also featured by rapid onset and development.
When there is vaginal bleeding with large bleeding amount, dark red blood and may be accompanied by mild abdominal pain, or when there is a sudden onset of persistent abdominal pain, soreness of loins, lumbago, and the stomach suddenly gets hard when touching it, you need to be alert to placental abruption and rush to the hospital, don’t hesitate!
Placenta of Different Shapes
The normal placenta is round or oval, the umbilical cord is attached to the surface of the placenta and planted between the edge and the center of the placenta, while there are also battledore placenta, annular placenta and velamentous placenta.
It refers to the condition that the umbilical cord is planted at the edge of the placenta, thus forming a battledore-like shape together with the placenta. Battledore placenta is actually more common in clinical practice. it is not a particularly abnormal condition and will not affect the safety of the mother and child, so the pregnant woman does not need to worry too much. However, the on-time maternity checkup, as well as the fetal heart monitoring, B ultrasound examination, self-counting fetal movements and other routine examinations are still required.
The annular placenta is also unlikely to affect the safety of pregnant woman and child. As the placenta is surrounded by fibrotic tissue and the fibrotic strips form a tire-like appearance, so it is known as an annular placenta. The annular placenta with a lower incidence rate usually results from the development of the placenta itself, and it does not affect placental function or fetal blood supply, so it does not usually cause adverse pregnancy outcomes either.
It is, as the name implies, a placenta that looks like a velamentum. What is distinctive in the velamentous placenta is that the umbilical cord is not planted in the center or paracentral area of the placenta, but in the fetal membranes outside the placenta, which makes the vessels of umbilical cord originally wrapped fan out with various branches and eventually connect to the edge of the placenta. These fan-shaped vessels resemble the canvas of a sailboat, so it is known as the velamentous placenta.
Although the name sounds pretty cool, it is actually dangerous. Since the umbilical cord is planted at the edge of the placenta, only a small number of blood vessels can be connected to the placenta, which leads to ischemia and blood loss in the cord, thus affecting the normal growth of the fetus. In addition, the blood vessels that are attached in the shape of a sail are more tense and prone to rupture, resulting in massive and rapid blood loss, which in turn increases the possibility of fetal hypoxia or death.
therefore, when you are diagnosed with velamentous placenta, please be ready to undergo a cesarean section at any time to welcome your baby.
The Types of Pregnant Women Who are More Likely to Get Placental Abnormality and Ways to Avoid It
l Advanced age
Elderly parturient women, namely, the primiparas aged 35 years or above. According to the research data from Society of Obstetricians and Gynaecologists of Canada, women’s reproductive capacity begins to decline gradually from the age of 30, and after the age of 37, it shows an extreme decline. However, in fact, in addition to the declined reproductive capacity, the elderly parturient women will also face the physical and mental changes and increased risks during pregnancy, as well as more difficult physical recovery after delivery. Placental abnormality is one of the risks of pregnancy that women of elderly parturient women face.
So, if you plan to have children, please start it as soon as possible, it’s good for both mothers and children!
According to a study involving 1,049 primiparas with abortion, the incidence of placental abnormalities was 10.01%. The increased incidence of placental abnormalities may be due to infection caused by uterine aspiration, deep dilatation and curettage or lax aseptic operation, which damage the endometrium and superficial muscular layer and cause the poor development of the uterine metaplasm during re-pregnancy and insufficient blood supply to the placenta, leading to a compensatory expansion of the placental area or compensatory depth of attachment to take in sufficient nutrients.
So, birth control must be required! You can choose any of the birth control measures such as contraceptive pill, condom, contraceptive ring, or male ligation. Do not take a chance and end up with an abortion.
l Assisted reproduction
According to a study on the relationship between assisted reproduction and placental abnormalities involving 360 pregnant women, the incidence of the placenta previa, placental abruption and velamentous placenta was higher in the assisted reproduction group than in the natural pregnancy group. In conclusion, the placental abnormalities were twice as likely to occur in the assisted reproduction group as in the natural pregnancy group.
Therefore, have a natural pregnancy if condition permits, and the process of conception is full of the sense of ceremony. If you cannot give birth naturally, do not force yourself to make it, or delay your plan to have children with a chilled attitude. You can have your baby with assisted reproductive technology and remember to have regular pregnancy checkups; in case of any placental abnormality, follow the doctor’s advice to take adequate measures to ensure the safety of both mother and child.
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 Chen Huaping, Li Jun, Guo Zhiwei et al. MRI Diagnosis of Prenatal Placental Abnormality to Late Pregnant Women [J]. Medical Journal of West China, 2017, 029(008): 1146-1149
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 Elizabeth Cochrane, et al. Assisted reproductive technologies (ART) and placental abnormalities. J Perinat Med. 2020 Oct 25; 48(8):825-828