Approach

Treatment should be thought of in three dimensions:

  • Degree of bleeding: none, mild to moderate, severe

  • Presence or absence of labour

  • Duration of pregnancy: first trimester, second trimester but not viable, viable but not term (preterm), term (age of viability varies depending on local resources).

Each of these dimensions should be considered separately and then together in making treatment decisions. As the degree of bleeding is often the controlling variable, it is useful to approach treatment according to bleeding severity.

Rhesus incompatibility

For all cases, the indication for anti-D immunoglobulin should be assessed.[55] If the woman is rhesus (Rh) negative, a Kleihauer-Betke test will help determine the degree of haemorrhage, and the need for and amount of anti-D immunoglobulin that is required for prophylaxis for Rh disease in subsequent pregnancies.[5][46]

In practice, anti-D immunoglobulin should be given at 28 weeks' gestation (when the fetal blood type is unknown or known to be Rh positive) or within 72 hours of delivery to a postpartum non-sensitised Rh-negative woman delivering an Rh-positive infant.[46]

In the UK, the National Institute for Health and Care Excellence and the British Society for Haematology advise that anti-D immunoglobulin may be administered as a single dose at 28 weeks' gestation, or as two doses at 28 weeks' and 34 weeks' gestation.[56][57]

Additional anti-D immunoglobulin may be required for fetomaternal haemorrhage (FMH) of >15 mL of fetal red blood cells or >30 mL of fetal whole blood.[46] An additional 10 micrograms of anti-D immunoglobulin should be given for every additional 0.5 mL fetal red blood cells. Quantitative testing for FMH may be considered following events potentially associated with placental trauma and disruption of the fetomaternal interface (e.g., placental abruption, blunt trauma to the abdomen, cordocentesis, PP with bleeding).[46]

Initial management of bleeding in placenta praevia

A 2017 meta-analysis determined that 52% of women with PP will experience bleeding from the genital tract in the second half of pregnancy.[58]

Unknown placental position

  • Not all women will have had ultrasounds during pregnancy that would have identified placental position, and some women present late in pregnancy without previous antenatal care.

  • In the presence of bleeding, and if the woman is haemodynamically stable enough to allow it, urgent ultrasound should be obtained to define placental anatomy.[37] If uterine tenderness is present, this may suggest placental abruption, which can co-exist with PP.

  • Treatment varies with the underlying condition; if PP is found (without abruption), the corresponding treatment approach below should be followed.[44][45]

Known PP

  • The primary and immediate goal of therapy is to stabilise the mother haemodynamically. The secondary goal is to ensure fetal survival.

  • A digital vaginal examination should not be performed, as this may turn severe bleeding into torrential bleeding.[1][15][44] Bleeding can increase from mild to severe over minutes, and it is therefore best to overestimate the degree of bleeding. Severe bleeding is usually obvious but occasionally blood can pool in the vagina (and then be expressed as large clots).

  • Continuous electronic fetal heart monitoring should be arranged as long as significant bleeding continues; fetal compromise (abnormal fetal heart tracing) is usually an indication of severe bleeding.[5][44]

  • Proceed to an immediate caesarean section if bleeding does not subside, or if there is evidence of significant fetal compromise.[1][2] Prophylactic intra-operative antibiotics are indicated routinely in caesarean sections.[2][15][39][44][59]

As for all cases of significant haemorrhage in pregnancy, ABC of key resuscitation guidelines should be followed.

  • Intravenous access should be obtained.

  • Administration of an antifibrinolytic (such as tranexamic acid) should be considered as soon as possible as they have been shown to have a survival benefit.[60]

  • Crystalloids and blood products should be administered as indicated; consider the risks of transmission of infectious diseases (which varies locally) in deciding on blood transfusion.

  • Type and screen and cross-match for at least 4 units of packed red blood cells (and inform transfusion service of possibility of need for massive transfusion). Follow with serial FBCs (frequency depends on degree of bleeding). Consider assessing international normalised ratio (INR)/partial thromboplastin time (PTT), fibrinogen, and fibrinogen degradation products if there is evidence of disseminated intravascular coagulation.

  • Transfusion of fresh frozen plasma and platelets should be considered, depending on the Hb level, platelet count, and level of coagulopathy.

After initial stabilisation of a bleed:

  • Urgent consultation with appropriately trained personnel should be obtained for further management. If bleeding subsides and if appropriate, the mother should be transferred to a centre where suitable obstetric and neonatal expertise is available. An ultrasound (or possibly, if previous uterine scarring, MRI) should be obtained to define placental anatomy. After stabilisation, outpatient care may be appropriate in some circumstances. This decision should be left to the consultant.[39][61]

Antenatal management of placenta praevia

The primary goal of therapy is to observe mother and fetus closely so that urgent intervention can be arranged if deterioration occurs.[1][2][15][39][44][59]

Expectant management

  • Women should be given advice about pelvic rest (e.g., no penetrative sexual intercourse or use of tampons) and advised to seek medical attention in case of significant bleeding (i.e., any bleeding beyond spotting).[1][4][15]

  • Women should be advised that they can bleed suddenly and severely and that they should remain within easy access to advanced medical care.[1][4][5][15][44]

  • Many low-lying placentas migrate during pregnancy and resolve spontaneously. If PP or a low-lying placenta are detected at the routine anatomical scan (typically 18 to 22 weeks' gestation) and there is no significant bleeding, a repeat ultrasound should be obtained at approximately 32 weeks.[1][2][38] If the placenta is now in normal position, no further investigations are indicated. If a low-lying placenta or a PP is detected, however, it is very unlikely to resolve spontaneously, and a further ultrasound should be arranged at 36 weeks to aid delivery planning.[1][2] If there is risk of placenta accreta spectrum (e.g., previous uterine scarring) then an ultrasound with colour flow Doppler imaging should be obtained.[2][3][4] Supplementary to this, MRI imaging may also be used to define the exact placental anatomy. The decision on the method and timing of imaging should be left to the consultant.

  • Depending on local expertise and resources, appropriate referral may be made to a centre at which suitable obstetric and neonatal expertise is available.

  • If delivery is planned or expected before 34 weeks' gestation, intravenous magnesium sulfate is recommended for neuroprotection of the baby.[62][63]​ Physicians electing to use magnesium sulfate for fetal neuroprotection should develop specific guidelines regarding inclusion criteria, treatment regimens, and concurrent tocolysis.[63] There is no evidence that magnesium sulfate has any value as a tocolytic agent, and its use should only be for neuroprotection in appropriate groups of women.[64]​​

  • If appropriate (24 to 34 weeks' gestation), the mother should receive corticosteroids to hasten fetal lung maturity.[65][66][67] The Society of Obstetricians and Gynaecologists of Canada (SOGC) recommends corticosteroid administration only if the risk of delivery within 7 days is determined to be very high.[1]

  • In women who have bled previously or are otherwise at high risk of bleeding (cervical shortening or dilation), hospitalisation until delivery may be indicated. This decision should be made depending on the individual circumstances of the case (time of year, distance from hospital, availability of transportation, etc.) and the availability of local resources.[1][2][15]

  • There is currently insufficient evidence to support the routine use of cervical cerclage in women with PP. However, cerclage may be considered on an individual basis <24 weeks' gestation, for example in those with cervical shortening or antenatal haemorrhage.[1]

Preterm labour

  • An attempt should be made to arrest labour, although the efficacy of this has not been well established.

  • The major purpose of tocolytic therapy is to prolong pregnancy in order to allow the administration of corticosteroids.[68][69]​ The secondary use is to allow time for transfer to a secondary or tertiary referral centre (if indicated and if the mother's condition is stable).

  • The American College of Obstetricians and Gynecologists (ACOG) advises against the use of tocolysis in the late preterm period (34 weeks to 36 weeks plus 6 days) for the purpose of enabling corticosteroids to be administered.[66]

  • If appropriate after initial stabilisation, the mother should receive intravenous magnesium sulfate (for neuroprotection of the baby) and antenatal corticosteroids (to mature fetal lungs).[63]​​[65][66][67]​​​​ The US Food and Drug Administration (FDA) recommends against using magnesium sulfate injection for more than 5 to 7 days to stop preterm labour in pregnant women (an off-label use), as it may lead to low calcium levels and bone problems in the fetus or baby. The UK-based Medicines and Healthcare products Regulatory Agency (MHRA) also recommends against any use of magnesium sulfate in pregnancy for more than 5 to 7 days. If prolonged or repeated use occurs during pregnancy (e.g., multiple courses or use for >24 hours), consider monitoring of neonates for abnormal calcium and magnesium levels and skeletal adverse effects.[70][71]​​ SOGC recommends corticosteroid administration only if the risk of delivery within 7 days is determined to be very high.[1]

  • Consider a repeat dose of corticosteroids if the mother remains at risk for preterm birth 7 or more days after the initial course of corticosteroids. [66][67][68][72] Repeat doses of antenatal corticosteroids seem to reduce the need for neonatal respiratory support, however compared with a single dose there may be no difference in serious morbidity or mortality outcomes for the baby. There is also an increased risk of low birthweight with repeat corticosteroids which is dose dependent.[67]

  • If the attempt to arrest labour is not successful, a caesarean section should be performed.

Placenta praevia at term

In general, PP after 36 weeks is an indication for caesarean section as the route of delivery.[1] The decision as to the timing of the caesarean section is based on the gestational age (which may be uncertain) and the presence of risk factors, including the degree of bleeding, the start of labour (and the associated degree of cervical dilation), the danger of blood transfusion (which varies locally), and the presence of adequate neonatal care.[1][2] In the presence of risk factors, caesarean section is recommended at 36 weeks to 36 weeks plus 6 days.[1][2][5] In the absence of risk factors, caesarean section is recommended at 37 weeks to 37 weeks plus 6 days.[1][2][5] Prophylactic intra-operative antibiotics are indicated routinely in caesarean sections.[2][15][39][44][59]

If the woman is in labour, an urgent caesarean section is indicated as bleeding may suddenly worsen. If possible, a surgeon experienced in the control of massive uterine haemorrhage and caesarean hysterectomy is preferred.[1][2]​ The mother should be warned about the possibility of operative complications, including caesarean hysterectomy.[1][2]​ Adequate blood (possibly autologous) should be available and the transfusion service should be informed that there may be large transfusion requirements.[1][2]​ The neonatal team should be alerted to the situation.

Low-lying placenta at term

The os-placental edge distance on ultrasound at 36 weeks' gestation is valuable in planning route of delivery.[1][2] When the placental edge is 11 to 20 mm from the internal cervical os, women can be offered a trial of labour with a high expectation of success.[1] Trial of labour can be considered in carefully selected women with an os-placental edge distance of ≤10 mm, providing it takes place in a facility with immediate access to an obstetrician, anaesthetist, neonatologist, and blood transfusion.[1]

The asymptomatic woman at term and in labour may be allowed to continue labour with careful monitoring and consultation in a 'double setup' situation (one that may be immediately converted to a caesarean section if bleeding becomes significant or if the fetus becomes distressed).[2][15][39][44][59]

If women with a placental edge 11 to >20 mm from the internal cervical os elect to have a caesarean delivery, optimal timing for the procedure is 39 weeks to 40 weeks plus 6 days.[1] In women with an os-placental edge distance of ≤10 mm, caesarean delivery should be timed for 37 weeks to 37 weeks plus 6 days in the presence of risk factors, or 38 weeks to 38 weeks plus 6 days in the absence of risk factors.[1] Earlier, urgent delivery may be required in extenuating circumstances, including if antenatal haemorrhage results in maternal haemodynamic compromise or an abnormal fetal heart rate, or if there is significant antenatal haemorrhage at ≥34 weeks' gestation.[1]

Miscarriage/termination

Miscarriage is not treated differently in the presence of PP. Elective termination (whether medical or surgical) in the first trimester does not differ in presence of PP. In the second trimester, however, surgical termination may be preferred.

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