Placenta previa refers to an obstetric complication that in most cases occurs as painless vaginal bleeding especially in the third trimester and is secondary to abnormal placentation that covers the cervix. When there is a complete coverage of the cervix, a complete Previa occurs (Joy, 2015). Joy (2015) stated that if the leading edge is below two centimeters from the cervix but not partially covering it, such a case presents the marginal Previa. Partial placenta previa occurs when the placenta covers a section of the cervix. In particular, placenta previa occurs when the placenta implantation occurs at the lower side of the uterus covering the whole or part of the cervix.
The uterus thins and spreads to accommodate the growing baby in the later stages of pregnancy (after 20 weeks). The thinning and spreading cause bleeding. Sex may also trigger bleeding in mothers with placenta previa. During labor, the cervix dilates to allow the baby to exit. However, when the mother has placenta previa, the dilation cause the placenta to tear leading to the bleeding.
Causes and risk factors
There are various possible causes of placenta previa. First, when the egg implants at the lower part of the uterus, the placenta develops at that point leading to complete or partial placenta previa. Further, when the mother has fibroids, the implantation of the egg may take place in the lower sections of the uterus leading to the placenta previa. Fundamentally, fibroids would reduce the uterine space increasing the chances of developing placenta previa.
Besides, the scarring of the uterine lining i.e. endometrium may also cause placenta previa (“Placenta previa,” 2016). Mothers with multiple pregnancies also have higher chances of developing placenta previa (“Placenta previa,” 2014). The mothers who have had six or more births are at greater risk of developing the placenta previa. Women above age thirty-five are also at higher risks. At times, the placenta may have inherent complications that would make it lower down and block the cervix.
Moreover, women who had previous uterine surgeries or cesarean delivery are at higher risk of developing placenta previa. At the same time, cigarettes smoking may render one vulnerable to the development of placenta previa. Mothers who had the same condition in previous pregnancies are also at higher risk as well as women pregnant with a male fetus.
There is little evidence of genetic links to placenta previa. However, since having multiple pregnancies places one at risk, women with such genetic lineages i.e. families with multiple pregnancies could be at higher risks of developing the placenta previa. There is no evidence of external environmental issues that makes one vulnerable to developing placenta previa. The same case applies to one's lifestyle.
Cresswell, Ronsmans, Calvert, and Fillipi (2013) stated that placenta previa prevalence rate was 5.2 per every 1000 pregnancies worldwide. There was regional variation. The study showed that in Asians had the highest prevalence rate of 12.2 per 1000 pregnancies, and reduced rates in Europe with 3.6 in every 1000 pregnancies, 2.9 and 2.7 per 1000 pregnancies in North American and Africa respectively.
Pathophysiology and diagnosis
As mentioned in the introduction, women with placenta previa bleed at the later stages of the pregnancy. It follows that the most classical diagnosis of the condition is bleeding. Any pregnant mother experiencing bleeding needs a quick medical attention to help stop the possible complications that may arise from the placenta previa. An ultrasound scan is among the best methods for diagnosing placenta previa. Besides that, one can feel the mother's belly so as to establish the position of the fetus. If the baby is sideways or presents bottom first, in one out of three such occurrences, the mother has placenta previa.
Placenta previa can lead to serious complication. First, the mother may suffer severe hemorrhage if there is no immediate medical care. The mother may experience shock from blood loss. Since the placenta provides the fetus with nutrients and oxygen, its tear would mean that the baby does not receive enough oxygen and food. The fetus may also lose a lot of blood that may in turn cause its death. As mentioned earlier, the placenta previa occurs when the placenta blocks part or the whole of the cervix making caesarean delivery as the only safe means of delivery. On top of that, the mother may experience premature labor, and that may lead to the birth of a premature baby. Premature babies are at higher risk of diseases. Hysterectomy is common when the mother has placenta previa.
As mentioned earlier women who have had a caesarean delivery, removal of fibroids through surgery, and have had more than six births at higher risks of developing placenta previa. Fundamentally, both caesarean delivery and the surgical removal of fibroids tend to cause scarring in the uterus. It follows that the women would be at a higher risk. The same case occurs even with normal delivery because the placenta leaves some scars after birth that affect the uterine lining increasing the danger of developing the condition.
Cresswell J. A., Ronsmans C., Calvert C., and Fillipi V. (2013). Prevalence of placenta praevia by world region: a systematic review and meta-analysis. Tropical Medicine and International Health. Volume 18 no 6 pp 712–724 June 2013. Retrieved on February 2, 2016 from http://onlinelibrary.wiley.com/doi/10.1111/tmi.12100/pdf
Joy S. (2015). Placenta previa. Retrieved on February 2, 2016 from http://emedicine.medscape.com/article/262063-overview
Placenta previa. (2014). Retrieved on February 2, 2016 from https://www.betterhealth.vic.gov.au/health/healthyliving/placenta-previa
Placenta previa. (2016). Retrieved on February 2, 2016 from https://www.betterhealth.vic.gov.au/health/healthyliving/placenta-previa