Low-Lying Placenta and Placenta Previa

low-lying placenta and placenta previa

Abnormal localization of the placenta.

The Placenta is the organ through which nutritional and metabolic exchange takes place between the mother and the fetus; it is a very complex structure, adhering to the inner wall of the uterus and which after being detached from this will be ejected in the terminal phase of childbirth call afterbirth (phase immediately subsequent to the birth). To Placenta, the organ critical to the fetus growth, have been attributed immunological and endocrinological competences.

The insertion anomalies such as Placenta Previa and Low-Lying Placenta can cause serious complications.

Its insertion is normally placed on the upper part of the Uterine Wall, far away from the Internal Uterine Orifice (IUO) and from the Uterus lower part that will become the Lower Uterine Segment (LUS). Both areas are involved in Uterine dilatation (opening) required to allow the fetus to pass through the birth canal and to born.

When its insertion is lower, it can reach the critical areas (IUO and LUS) involved in the opening of the Uterus lower part, configuring the fearsome pathological situation called Placenta Previa. Its incidence is about one in 200 pregnancies and leads serious risks to both the fetus and the mother.

Symptoms are characteristic and consist of sometimes scarce, at other times very abundant, bright red blood vaginal discharges. These bleeding occur suddenly, often at night or after sexual activity, almost always painlessly. It is typical of the third trimester of pregnancy, but it may start early at first or second quarters. For this reason, in presence of painless vaginal bleeding during pregnancy, it is always good to consider the possible presence of a Placenta Previa. When blood loss is accompanied by pain, specialists must make a rapid differential diagnosis with retro-placental Hematoma, placental abruption and threat of premature birth (Uterine contractions); all conditions relevant to their severity, sometimes associated with Placenta Previa.

Placenta Previa is mainly diagnosed by Ultrasound. In fact, only after the introduction of this diagnostic technique that was easily possible to study the placental morphology and its relationship in terms of extension and localization with the Uterine Wall. Ultrasound allows early diagnosis and monitoring of relations between Placenta, Lower Uterine Segment, internal opening of the cervical canal (OUI) during gestation. Transvaginal ultrasound (TV), based on the use of an ultrasound probe introduced into the Vagina and Cervix approached proved to be particularly useful for these purposes; it is a safe, accurate and low cost procedure.

It has been proposed a screening to all pregnant women before the 20th week; I personally agree with this attitude and I recommend to my patients a Cervix TV echo check already at the18th week, particularly when there have already been small bleeding, threatened abortion or otherwise there are Placenta Previa risk factors.

PLACENTA PREVIA RISK FACTORS
  • Maternal age (at 35 is three times more frequent than at 25)Number of pregnancies (great multiparous risk is of 5%)Cigarette smoking
  • Multiple pregnancies
  • Previous surgery on the uterus including cesarean section (1 TC increases of 0.65%, 2.2% TC 3, 4, or more than 10% TC)
  • Previous placenta previa (4-8% risk of recurrence)

It must be said that the finding of a low-lying placenta before the 24th week has an incidence of 20-28% of all pregnancies and that this percentage drops to 18% soon after this time, then further reduced by up to 3%. The decrease is related to the slope (migration) of the Secondary Placenta Plant to the Uterus development and to the formation of SUI. For this reason Diagnosis of Placenta Previa should be put only after 26-28 weeks (when SUI is formed). Until then it will be good to continue to use the name of Low-Lying Placenta. There is also a fair percentage of missed diagnosis cases: it is estimated that this occurs in approximately 7% of cases, particularly when the placenta is posterior, the fetal head covers the lower placental insertion and it has not been used a transvaginal probe .

PLACENTA PREVIA CLASSIFICATION
  • Central total (completely covers the IUO)
  • central part (partially covers the IUO)
  • marginal (comes close to the margin of IUO, not cover it)
  • side (SUI reaches but is at least 2.5 cm   from IUO)

Placenta Previa risks are fetal and maternal. This condition is in fact associated with a series of fearsome and dangerous complications such as premature birth, sudden and profuse bleeding and placental abruption. In particular, bleeding can endanger the Fetus life and in some cases even mother’s life. Although a Placenta Previa can cause bleeding in the first and second quarter and in the third quarter, it is typically around the 28th week that appears the first abundant vaginal bleeding characterized by a sudden bright red blood in pain absence. Sometimes pain can also occur frequently linked to complications such as placental abruption and / or beginning of a uterine contractile activity (threat of premature birth).

For these reasons a low-lying Placenta detection requires a special attention that certainly will be increased in cases of exact Placenta Previa diagnosis.

In most cases, mode of birth is done by emergency or elective caesarean section; this fact has to be considered the birth elective mode. Only in selected cases, in which Placenta is marginal or lateral and Fetus is in a cephalic presentation, after an adequate information on the risks, spontaneous birth can be considered, but always in a well-prepared and ready for the maternal and neonatal emergency.

RECOMMENDATIONS FOR PATIENTS WITH PLACENTA PREVIA
  • Avoid sexual activity, effort, travel, sports
  • Strictly follow checks and medical prescriptions
  • Always carry your ID card, blood type and Rh factor
  • Maintain close contact with Specialist Practitioner and Hospital Centre of reference. Do not stray too far from the hospital and stay in an Emergency Service readily available area.
  • When you are at home always try to have a family near you
  • If blood loss is observed, remain calm, lie down and stand on the left side (safety position) while your family will alert the rescue.

The clinical and instrumental (ultrasound) controls in these patients will have a different cadence unlikely other pregnancies and in many cases will require hospitalization.

The treatment and possible hospitalization aim is to reach a Fetus sufficient maturity with a minimum risk of peri-natal outcomes, safeguarding the health of the mother. The high probability of preterm delivery imposes an admission selection at Hospital Facilities with a Neonatal Intensive Care Unit and Intensive Care; Hospital should also always have adequate emergency services (CPR) and a transfusion center nursery.

The waiting strategy for Placenta Previa is possible and particularly indicated before the 34th gestational week in stable patients (good condition), without or with very modest and limited bleeding and not suffering Fetus. It is the result of a thorough clinical evaluation and a careful risk-benefit balance. In these cases, it is usually undertaken a corticosteroid therapy to accelerate fetal lung maturity and tocolytic (inhibiting uterine contractions) if there is a premature birth threat.

Hospitalization is the measure of choice in many cases, especially when it is prolonged and occurs after the 28th week. Waiting at home is possible, even if reserved for selected patients who live or can linger in the hospital proximity (suitable for assistance).

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Filiberto Di Prospero
Medical Doctor, Consultant in Gynecology and Obstetrics, Endocrinology and Metabolism. Director of Gynecologic Endocrinology Unit at Civitanova Marche General Hospital (Italy). Private clinics in Civitanova Marche, Rome and Milan.

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