A 21–year-old female has been placed on a MgSO4 infusion after she had an eclamptic seizure.
Which ONE of the following is TRUE regarding the use of MgSO4 in pregnancy?
Answer: D: MgSO4 is indicated in pregnant patients with severe preeclampsia to prevent seizures and in eclamptic patients for the treatment and prophylaxis of seizures. Routine monitoring of serum levels is not useful, as there is no ‘therapeutic range’ established for its use in eclampsia. Adverse effects include flushing, nausea, drowsiness and weakness with respiratory depression and respiratory and cardiac arrest the most serious complications. However, the adverse effects follow a dose response; deep tendon reflexes are lost at a serum magnesium level of 10 mEq/L, respiratory depression occur at 15 mEq/L and cardiac arrest at more than 15 mEq/L. This dose response relationship means that clinical monitoring should ensure that toxicity and adverse effects are avoided. For this reason, deep tendon reflexes and respiratory rate should routine be monitored and can be used as an early indicator of toxicity.
Magnesium is excreted in the urine and raised serum levels will quickly occur in patients with impaired renal function and be at risk of significant adverse effects if the dose is not reduced. Decreased urine output may therefore lead to earlier toxicity and measuring hourly urine output should be included in the clinical monitoring. Magnesium levels should be checked if there is loss of deep tendon reflexes or in the presence of renal dysfunction. Nevertheless, some clinicians still prefer to routinely measure magnesium levels to detect toxicity. If toxicity does develop, calcium gluconate is an effective antidote.
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Regarding drug use in pregnancy and lactation, which ONE of the following is the MOST appropriate?
Answer: A: Paracetamol is the analgesic of choice in pregnancy and lactation but is often inadequate for severe migraine attacks. Metoclopramide is safe to use in pregnancy, and may be added to paracetamol to increase its effectiveness. Dihydroergotamine and the triptans should be avoided throughout pregnancy. NSAIDs can be continued into the second trimester (up to 32 weeks) as there are no data suggesting increased fetal malformations.
However, NSAIDs should not be used in late pregnancy because they can cause premature closure of the fetal ductus arteriosus, delay labour and birth, or cause oligohydramnios via an effect on fetal renal function. NSAIDs are classified as compatible with breastfeeding. Diclofenac or ibuprofen are the preferred drugs. Oxycodone is another medication that is commonly prescribed postpartum that is compatible with breastfeeding if given as occasional doses.
Trichomoniasis in pregnancy is associated with adverse pregnancy outcomes (premature rupture of membranes, preterm delivery and low birth weight) and a single dose of metronidazole 2 g orally is generally recommended. However, metronidazole treatment does not necessarily result in a reduction in perinatal morbidity and some trials suggest the possibility of increased prematurity, particularly if treatment is given during the midtrimester. Gentamicin has a TGA pregnancy classification D and should be avoided where possible. It is often used in severe sepsis in pregnancy where the benefits outweigh the risks. A cephalosporin would be a more appropriate antibiotic in the setting of pyelonephritis. Gentamicin is compatible with breastfeeding but may cause diarrhoea in the infant.
Regarding abruptio placentae in pregnancy, which ONE of the following is TRUE?
Answer: C: The clinical presentation of abruption varies widely from totally asymptomatic cases to those where there is fetal death with severe maternal morbidity. The classic description of placental abruption is painful vaginal bleeding, severe uterine pain or tenderness, uterine hypertonicity and hypotension. It is important to realise, however, that severe abruption may occur with neither or just of one of these signs. Additionally, symptoms can be subtle with minimal or no bleeding and only minimal abdominal cramping. The amount of vaginal bleeding correlates poorly with the degree of abruption. Back pain may be the only symptom, especially when the placenta is posteriorly located. The severity of symptoms depends on the location of the abruption, whether it is revealed or concealed, and the degree of abruption. There are often features of fetal distress, with fetal death occurring in most cases in which there is >50% placental separation.
Placental abruption is often associated with the development of disseminated intravascular coagulation (DIC). The risk of DIC is highest when there is such a large placental detachment as to cause fetal death. Haemorrhage associated with DIC leads to further consumption of coagulation factors, setting off a vicious cycle. Bleeding may occur into the uterine myometrium, leading to a beefy boggy uterus called a Couvelaire uterus. The normal fibrinogen level in pregnancy is 4–4.5 g/L; values below <3 g/L indicates significant consumption of coagulation factors.
Ultrasonography has a limited sensitivity in detecting abruptio placenta, with a reported negative predictive value of 63–88%. The ultrasonographic appearance of abruption depends to a large extent on the size and location of the bleed as well as the duration between the abruption and the time the ultrasonographic examination was performed, as the echogenicity of fresh blood is so similar to that of the placenta. Placental abruption is primarily a clinical diagnosis. Ultrasound is purely an adjunct in the diagnosis and helps exclude other causes of vaginal bleeding such as placenta praevia.
Regarding antepartum haemorrhage in the third trimester of pregnancy, which ONE of the following is TRUE?
Answer: A: In contrast to abruption, the classic presentation of placenta praevia is painless, bright red vaginal bleeding occurring at the end of the second trimester. Bleeding is usually painless because the blood is expelled and does not cause uterine distension. Fortunately, this ‘sentinel bleed’ is rarely massive and usually stops spontaneously, though it often recurs and may become profuse during labour. The degree of bleeding is often proportional to the degree of haemodynamic compromise. Some degree of uterine irritability is present in about 20% of the cases, which may make it difficult to distinguish from abruptio.
Digital vaginal examination should be avoided in all patients presenting with antepartum haemorrhage in the second half of the pregnancy until the diagnosis of placenta praevia is excluded as the possibility of tearing or dislodging a placenta praevia may result in profuse and potentially fatal haemorrhage. Ultrasound is the diagnostic procedure of choice for diagnosing placenta praevia in any patient who presents with vaginal bleeding during the latter half of pregnancy. Transabdominal ultrasound has a sensitivity of 95%. Multiple studies have shown that transvaginal ultrasound is safe and more accurate than transabdominal ultrasound. Once an ultrasound has excluded placenta praevia, a careful speculum examination may be performed to look for other causes of bleeding. In the rare case where an ultrasound cannot exclude placenta praevia or is not available, a digital and speculum examination should be performed in the operating theatre with the patient prepared and draped for an urgent caesarean section.
Vasa praevia refers to the velamentous insertion of the cord below the presenting part of the fetus. Normally, the vessels run from the middle of the placenta via the umbilical cord to the fetus. Velamentous insertion means that the vessels, unprotected by Wharton’s jelly, traverse the membranes before they come together into the umbilical cord. These unprotected vessels may rupture at any time during pregnancy but usually in association with rupture of the amniotic membranes. When this occurs, bleeding is from the fetus, which may quickly lead to fetal exsanguination and death. Perinatal mortality with vessel rupture ranges from 75 to 100%.
A 28-year-old female presents in labour. After delivery of the head, you notice the chin retracts tightly into the perineum.
Which ONE of the following is the MOST appropriate answer?
Answer: D: Shoulder dystocia refers to impaction of the fetal shoulders at the pelvic outlet occurring after delivery of the head. Typically, the anterior shoulder is trapped behind the symphysis pubis, which leads to delay of delivery of the rest of the infant. In addition, the fetal shoulders are in the vertical position rather than the normal oblique position. Impaction of the fetal shoulders and thorax in the maternal pelvis prohibits adequate respiration, and compression of the umbilical cord frequently compromises fetal circulation. Fetal hypoxia results from impaired respirations due to impaction of the fetal shoulders and thorax in the maternal pelvis. Fetal circulation is compromised due to compression of the umbilical cord as well as compression of the neck and central venous congestion. The aim is to deliver the fetus under 5 minutes to prevent asphyxia.
Various manoeuvres exist and can be employed in an attempt to dislodge the anterior shoulder. With the McRoberts’ manoeuvre the mother is placed in the extreme lithotomy position, with legs sharply flexed up to the abdomen. The McRoberts’ manoeuvre does not change the actual dimension of the maternal pelvis. Rather, the manoeuvre straightens the sacrum relative to the lumbar spine, allowing cephalic rotation of the symphysis pubis sliding over the fetal shoulder. Commonly, suprapubic pressure is applied by an assistant, directing the anterior shoulder downward and laterally in an attempt to rotate the shoulder and infant under the symphysis pubis. Fundal pressure should never be applied, as this will further impact the shoulder on the pelvic rim.
Shoulder dystocia is typically a ‘bony’ obstruction and not a result of obstructing soft tissue. Management by episiotomy has been associated with an increase in the rate of perineal trauma without benefit of reducing the occurrence of neonatal depression or brachial plexus palsy. The decision to cut a generous episiotomy must be based upon clinical circumstances, such as a narrow vaginal fourchette in a primigravid patient or the need to perform fetal manipulation. Draining the bladder with a Foley catheter may give more room anteriorly. Other manoeuvres include Wood’s corkscrew manoeuvre, Rubin’s manoeuvre and delivery of the posterior arm.
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