Pregnancy related complications: Pearls and pitfalls
Part 1 of this 3 part series, (found here) dealt with the principles of resuscitation of the critically injured pregnant trauma patient. This next post is going to deal with pregnancy related complications and how to manage them.
Placental abruption
Placental abruption is the most common pregnancy related complication following trauma, occurring in up to 7% of all trauma. It occurs in up to 50% of all seriously injured pregnant women, but can also occur in relatively minor trauma, in 4% of these cases. It is therefore crucial that we always consider placental abruption in every pregnant trauma patient.
Placental abruption occurs when the placenta is sheared off the wall of the uterus following impact to the abdomen and pelvis. It typically occurs after 20 weeks of pregnancy but may occur as early as 16 weeks of gestation following trauma.
The consequences of abruption are often devastating. Fetal complications are: perinatal asphyxia, intrauterine fetal death, cerebral palsy and preterm labour. Maternal complications include disseminated intravascular coagulopathy (DIC), haemorrhagic shock and an increased risk of post-partum haemorrhage. DIC may complicate 10% of abruptions, so a DIC screen is recommended in some guidelines.
The symptoms and signs of placental abruption typically occur soon after the impact, but may present up to 24 hours later.
The classic (therefore uncommon!) presentation of placental abruption is abdominal pain, vaginal bleeding and reduced fetal movements. Severe abruption will manifest as maternal shock as well. The abdominal pain is often constant and severe. Remember that if vaginal bleeding is present, a sonar to exclude placenta praevia should be done prior to vaginal examination.
Unfortunately, absence of abdominal pain does not entirely exclude abruption.
Concealed bleeding may occur, meaning that there may be no PV bleeding at all. Ultrasound is unreliable in abruption as the retroplacental clot quickly becomes isoechoic to the placenta, making the abruption difficult to see.
So how do we exclude this serious complication?
CTG monitoring is the most reliable test to help rule out the diagnosis.
Consider CTG if:
Viable gestational age: Fetus at or close to a viable gestation (this is Country specific but is generally approximately 24 weeks in high income countries, and 26-28 weeks in low to middle income countries.
Mechanism of injury is suggestive for abruption: A fall onto the abdomen, direct blow or a vehicle accident. Even if the impact seems relatively minor, a CTG should be done in these cases.
A minimum of 4 hours of CTG monitoring is needed. This normally requires consultation with Obstetrics.
In minor trauma, if the CTG shows a healthy fetal heart trace and no more than 1 uterine contraction every 15 minutes, the patient may be discharged with Obstetric follow-up. Studies have shown no adverse events using this guideline. Non-reassuring traces, or more contractions than 1 every 15 minutes requires at least 24 hours of CTG monitoring and admission to hospital.
The Kleihauer Betke test is a blood test done on maternal blood that detects the presence of fetal haemoglobin, indicating that fetal maternal haemorrhage has occurred. The role of this test for detecting placental abruption has been debated in the literature. The 2010 EAST guidelines for trauma in pregnancy still recommend its use. The 2015 Canadian guidelines do not recommend it as a screening test for abruption as it may be positive even in the absence of abruption and negative despite abruption being present. The Kleihauer Betke test has an important role in Rhesus negative pregnant women following trauma and is discussed below.
Preterm labour
Preterm labour is defined as the onset of labour prior to 37 completed weeks of gestation. Signs of preterm labour include the presence of a show, uterine contraction, and effacement and dilation of the cervix. Abruption, maternal hypoxia and bleeding can all precipitate preterm labour.
Uterine contractions post trauma are common but stop in 90% of cases. More than 1 contraction every 15 minutes of the tocogram suggests the onset of preterm labour, which is confirmed by progressive dilation and effacement of the cervix.
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Premature rupture of the membranes (PROM) can occur following trauma, with or without the onset of preterm labour. PROM is confirmed by the presence of liquor draining, and a positive ferning test.
Further management of preterm labour in the setting of trauma will be guided by the Obstetricians, with the mother’s wellbeing being the priority.
Patients being discharged from the Emergency department should be counselled about the signs of preterm labour and the increased risk of preterm labour following trauma. They should always be referred to the Obstetrician for further follow-up.
Uterine Rupture
One often worries about uterine rupture following trauma but this is thankfully a rare complication, occurring in less than 0.1% of maternal trauma. Fetal trauma is also very rare, as the fetus is well protected by the uterus.
Signs of rupture include: haemorrhagic shock, peritonism, palpable fetal parts, and frequently an absent fetal heart beat with free fluid visible in the abdomen and pelvis on ultrasound. If suspected this is an Obstetric emergency that requires emergency laparotomy.
Feto-maternal haemorrhage and Rhesus Isoimmunisation
Rhesus iso-immunisation is the development of maternal anti-D antibodies in an Rh negative mother following exposure to fetal Rh positive blood. The antibodies can cause haemolytic disease of the newborn in subsequent pregnancies where the fetus is Rh positive. Complications such as stillbirth and hydrops fetalis may also occur. Blood group typing should always be done in pregnant trauma patients, and anti-D administered if the mother is Rh negative.
The Kleihauer Betke test is done in Rh negative patients to determine the amount of fetal blood in the mother’s circulation. This can help to determine if a larger dose of anti-D is required.
In summary
- Placental abruption is the most common complication following trauma in pregnancy.
- The CTG is the best test to screen for placental abruption and should be done for a minimum of 4 hours in patients with a viable pregnancy and suggestive mechanism of injury.
- Blood typing should be done on every pregnant patient. If the patient is Rh negative, anti-D should be administered to prevent rhesus iso-immunisation.
Click on the title below to read the other posts in this three part series:
Trauma in Pregnancy Part 1: Resuscitating the pregnant trauma patient
References
Practice management guidelines for the diagnosis and management of injury in the Pregnant patient: The EAST Practice Management Guidelines Work Group:
