Chapter 13 Common Medical Disorders Associated with Pregnancy
Cardiac disease
In most pregnancies, heart disease is diagnosed before pregnancy. There is, however, a small but significant group of women who will present at an antenatal clinic with an undiagnosed heart condition. Cardiac disease takes a variety of forms. Those more likely to be seen in pregnancy are:
The most common congenital heart defects found in pregnancy are shown in Box 13.1. Some acquired heart conditions are listed in Box 13.2.
Changes in cardiovascular dynamics during pregnancy
In normal pregnancy the haemodynamic profile alters in order to meet the increasing demands of the growing fetoplacental unit. Although this increases the workload of the heart quite significantly, normal, healthy pregnant women are able to adjust to these physiological changes easily. In women with coexisting heart disease, however, the added workload can precipitate complications.
The haemodynamic changes commence early in pregnancy and gradually reach their maximum effect between 28 and 32 weeks.
During labour there is a significant increase in cardiac output as a result of uterine contractions.
In the 12–24 hours following birth there is further alteration with the shift of blood (approximately 1 litre) from the uterine to the systemic circulation.
Diagnosis
The recognition of heart disease in pregnancy may be difficult, as many of the symptoms of normal pregnancy resemble those of heart disease. The signs and symptoms of cardiac compromise are listed in Box 13.3.
Laboratory tests can assist with the diagnosis of cardiac disease and determine the type of lesion, together with giving an assessment of current functional capacity. Tests include:
Preconception care
Women with known heart disease should seek advice from a cardiologist and an obstetrician before becoming pregnant, so that the risks of the condition can be discussed.
Antenatal care
The symptoms of normal pregnancy, together with the haemodynamic changes, can mimic the signs and symptoms of heart disease. Maternal investigations should be carried out prior to and at the onset of pregnancy in order to gain baseline referral points.
Management
All pregnant women with heart disease should be managed in obstetric units via a multidisciplinary approach involving midwives, obstetricians, cardiologists and anaesthetists. The aim is to maintain a steady haemodynamic state and prevent complications, as well as promote physical and psychological wellbeing. Visits to a joint clinic run by a cardiologist and obstetrician are usually made every 2 weeks until 30 weeks’ gestation and weekly thereafter until birth. At each visit functional grading is made according to the New York Heart Association classification and the severity of the heart lesion is assessed by clinical examination. Evaluation of fetal wellbeing will include:
ultrasound examination to confirm gestational age and congenital abnormality
assessment of fetal growth and amniotic fluid volume, both clinically and by ultrasound
monitoring the fetal heart rate by cardiotocography (CTG)
measurement of fetal and maternal placental blood flow indices by Doppler ultrasonography.
Intrapartum care
The first stage of labour
Vaginal birth is preferred unless there is an obstetric indication for caesarean section. Optimal management involves monitoring the maternal condition closely. This will include the measurement of:
Pulse oximetry, insertion of a central venous pressure (CVP) catheter and electrocardiogram (ECG) monitoring may be utilised.
Fluid balance
Women with significant heart disease require care to be taken concerning fluid balance in labour. Indiscriminate use of intravenous crystalloid fluids will lead to an increase in circulating blood volume, which women with heart disease will find difficult to cope with and they may easily develop pulmonary oedema.
Pain relief
It is important to consult a doctor before administering any form of pain-relieving drug to a woman with a heart condition. In the majority, an epidural would be the analgesia of choice.
Positioning
Cardiac output is influenced by the position of the labouring woman. It is preferable for an upright or left lateral position to be adopted.
Preterm labour
If a woman with heart disease should go into labour prematurely, then beta-sympathomimetic drugs are contraindicated.
The second stage of labour
This should be short without undue exertion on the part of the mother.
The midwife should encourage the woman to breathe normally and follow her natural desire to push, giving several short pushes during each contraction.
Forceps or ventouse may be used to shorten the second stage if the maternal condition deteriorates.
Care should be taken when the woman is in the lithotomy position, as this produces a sudden increase in venous return to the heart, which may result in heart failure.
Postnatal care
During the first 48 hours following birth the heart must cope with the extra blood from the uterine circulation. Close observation should identify early signs of infection, thrombosis or pulmonary oedema.
Breastfeeding is not contraindicated.
Discharge planning is particularly important for women with heart disease. The woman and her partner will need to discuss the implications of a future pregnancy with the cardiologist and obstetrician.
Respiratory disorders
Asthma
Pregnancy does not consistently affect the maternal asthmatic status; some women experience no change in symptoms whereas others have a distinct worsening of the disease.
Antenatal care
The main anxiety for women and those providing care is generated by the use of medication and the fear that this may harm the fetus.
To date all medications commonly used in the treatment of asthma, including systemic steroids, are considered safe and it is crucial that therapy is maintained during pregnancy in order to prevent deterioration of the condition and precipitation of adverse pregnancy events.
The lynchpin of management is the use of peak expiratory flow rates (PEFR) to monitor the level of resistance in the airways caused by inflammation or bronchospasm, or both.
Intrapartum care
If an asthma attack does occur, it should be treated with the same rapidity and medication as an attack outside of pregnancy.
Intravenous, intra-amniotic and transcervical prostaglandins should be avoided in pregnancy and labour because of their bronchospasmic action.
Any woman who has received corticosteroids in pregnancy should have increased doses for the stress of labour.
Cystic fibrosis
Cystic fibrosis (CF) is an autosomal recessive disorder affecting the exocrine glands that causes production of excess secretions with abnormal electrolyte concentrations, resulting in the obstruction of the ducts and glands.
Prepregnancy care
When planning a pregnancy, a woman with CF and her partner should have genetic counselling.
Although pregnancy appears to be well tolerated in women with pre-existing mild pulmonary dysfunction, morbidity and mortality are increased in women with pancreatic insufficiency or moderate to severe lung disease, or both.
Intrapartum care
During labour close monitoring of cardiorespiratory function will be required and an anaesthetist should be involved at an early stage.
Fluid and electrolyte management requires careful attention, as women with CF may easily become hypovolaemic from the loss of large quantities of sodium in sweat.
Epidural analgesia is the recommended form of pain relief in labour and general anaesthesia should be avoided.
Postnatal care
Women should be cared for in a high-dependency unit and should be closely monitored, as studies have highlighted that cardiorespiratory function often deteriorates following birth.
Breastfeeding is not contraindicated; however, in order for this to be successful, women need to be well nourished and maintain an adequate calorie intake.
Pulmonary tuberculosis
Tuberculosis (TB) is caused by the tubercle bacillus, Myobacterium tuberculosis. The lungs are the organ most commonly affected, although the disease may involve any organ.
Management
Standard antituberculous therapy should be used to treat TB in pregnancy. TB is treated in two phases:
In the first phase, rifampicin, isoniazid and pyrazinamide are given daily for the first 2 months.
In the second (continuation) phase, rifampicin and isoniazid are taken for a further 4 months.
These drugs are considered to be safe and are not associated with human fetal malformations. Attention should also be given to rest, good nutrition and education with regard to preventing the spread of the disease. TB is usually rendered non-infectious after 2 weeks of treatment.
Postnatal care
Babies born to mothers with infectious TB should be protected from the disease by the prophylactic use of isoniazid syrup 5 mg/kg/day for 6 weeks and should then be tuberculin tested.
If the tuberculin test is negative, bacille Calmette–Guérin (BCG) vaccination should be given and drug therapy discontinued.
If the test is positive, the baby should be assessed for congenital or perinatal infection, and drug therapy should be continued if these are excluded.
Breastfeeding is contraindicated only if the mother has active TB.
It is advisable for a woman with TB to avoid further pregnancies until the disease has been quiescent for at least 2 years. The woman needs to be aware that rifampicin reduces the effectiveness of oral contraception.
Renal disease
Asymptomatic bacteriuria
A diagnosis of asymptomatic bacteriuria (ASB) is made when there are more than 100 000 bacteria per millilitre of urine. All women should be screened for bacteriuria using a clean voided specimen of urine at their first antenatal visit.
If ASB is not identified and treated with antibiotics, 20–30% of affected women will develop a symptomatic urinary tract infection such as cystitis or pyelonephritis. These infections represent a significant risk for both mother and fetus and there is evidence to suggest that they may play a role in the onset of preterm labour.
Pyelonephritis
Management
Refer to a doctor; admit to hospital.
Obtain a midstream specimen of urine (MSU) to test for culture and sensitivity.
Give intravenous antibiotics followed by oral antibiotics once the pyrexia has settled.
Record fluid balance; intravenous fluids may be required.
Maintain 4-hourly observation of temperature and pulse.
Prevent complications of immobility, e.g. deep vein thrombosis.
Repeat cultures 2 weeks after completion of antibiotics and monthly until birth.
Chronic renal disease
In order to determine the impact of pregnancy on a woman with chronic renal disease, the following factors need to be considered:
Type of pre-existing renal disease.
General health status of the woman.
Presence or absence of hypertension.
If renal disease is under control, the maternal and fetal outcome is usually good. In some instances renal function may deteriorate and the chance of pregnancy complications subsequently rises.
Care and management
The aim of pregnancy care is to prevent deterioration in renal function. This will necessitate more frequent attendance for antenatal care and close liaison between the midwife, obstetrician and nephrologist.
Renal function is assessed on a regular basis by measuring serum urate levels, serum electrolyte and urea, 24-hour creatinine clearance and serum creatinine.
Screen for glycosuria, proteinuria, haematuria, urinary tract infection and anaemia.
Monitor for the emergence and severity of hypertension and pre-eclampsia.
Fetal surveillance includes fortnightly ultrasound scans from 24 weeks, Doppler flow studies and daily fetal activity charts.
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