8.1 Pre-existing Medical Conditions in Pregnancy (Diabetes, Cardiac, Epilepsy, Renal)

Pre-existing Medical Conditions in Pregnancy (Diabetes, Cardiac, Epilepsy, Renal)

Maternal medical disorders pre-dating pregnancy represent an increasingly prevalent challenge in contemporary midwifery. Data from the MBRRACE-UK (Mothers and Babies: Reducing Risk through Audits and Confidential Enquiries across the UK) confidential enquiries consistently demonstrate that indirect causes—pre-existing medical conditions exacerbated by pregnancy—account for more than half of all maternal deaths in the UK. Midwives play a pivotal role in early risk stratification, coordinating multidisciplinary care, recognising subtle signs of physiological decompensation, and ensuring that evidence-based interventions are instituted without delay.

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The Multidisciplinary Care Model in Complex Antenatal Care

Pregnant women with pre-existing chronic conditions must not receive fragmented or siloed care. National guidelines mandate a multidisciplinary team (MDT) framework coordinated by a named consultant obstetrician with expertise in medical disorders, a specialist physician (e.g., diabetologist, cardiologist, nephrologist, or neurologist), an obstetric anaesthetist, and a specialist midwife.

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Pre-existing Diabetes Mellitus (Type 1 and Type 2)

Pre-existing diabetes (Type 1 and Type 2) significantly elevates the risks of congenital malformations, miscarriage, pre-eclampsia, fetal macrosomia, stillbirth, birth trauma, and neonatal metabolic derangements. Care is guided by NICE guideline NG3 (Diabetes in pregnancy).

1. Pre-conception Care & Optimisation

• Glycaemic Targets: Women should aim for an HbA1c level <48 mmol/mol (6.5%) prior to conception without causing frequent or severe hypoglycaemia. An HbA1c exceeding 86 mmol/mol (10%) confers such extreme teratogenic risk (sacral agenesis, complex cardiac defects, neural tube defects) that women should be strongly advised to defer pregnancy and use reliable contraception until control improves.
• High-Dose Folic Acid: Women with pre-existing diabetes must be prescribed folic acid 5 mg daily (high dose) from preconception until 12 completed weeks of gestation to mitigate the elevated risk of neural tube defects.
• Medication Reconciliation: Potentially teratogenic medications—notably angiotensin-converting enzyme (ACE) inhibitors, angiotensin receptor blockers (ARBs), and statins—must be discontinued prior to conception or immediately upon pregnancy confirmation, substituting pregnancy-safe alternatives such as labetalol or methyldopa if antihypertensive therapy is required.

2. Organ Surveillance & Baseline Assessment

• Retinal Assessment: Digital retinal screening should be offered at the initial booking appointment and repeated at 28 weeks' gestation (or at 16–20 weeks if diabetic retinopathy was detected at booking). Rapid optimisation of glycaemia can paradoxically cause transient worsening of proliferative retinopathy, which may require urgent ophthalmological laser photocoagulation.
• Renal Assessment: Baseline renal function must be assessed at booking: serum creatinine, estimated glomerular filtration rate (eGFR), and urinary albumin:creatinine ratio (ACR) or protein:creatinine ratio (PCR). A urinary ACR >30 mg/mmol or estimated GFR <45 mL/min/1.73m² warrants urgent nephrology referral.

3. Antenatal Glycaemic Management & Continuous Glucose Monitoring

• Continuous Glucose Monitoring (CGM): NICE NG3 recommends offering real-time continuous glucose monitoring (rtCGM) to all pregnant women with Type 1 diabetes to improve maternal glycaemia, reduce neonatal hypoglycaemia, and lower the incidence of large-for-gestational-age infants.
• Self-Monitoring Capillary Blood Glucose Targets:
  • Fasting: below 5.3 mmol/L (above 4 mmol/L if taking insulin or glibenclamide)
  • 1 hour postprandial: <7.8 mmol/L (or 2 hours postprandial: <6.4 mmol/L)
• Gestational Insulin Dynamics: During the first trimester, enhanced insulin sensitivity and early pregnancy nausea increase the risk of severe maternal hypoglycaemia; glucagon emergency kits must be supplied, and family members trained. In the second and third trimesters, rising levels of human placental lactogen (hPL), progesterone, and cortisol provoke dramatic insulin resistance, requiring insulin dose increases of 50% to 100% above baseline.
• Diabetic Ketoacidosis (DKA): Pregnant women with Type 1 diabetes are at heightened risk of DKA, which can develop rapidly and at lower or even near-normal blood glucose levels (euglycaemic DKA) because of accelerated starvation ketosis and the reduced buffering capacity of the compensated respiratory alkalosis of pregnancy. NICE NG3 advises testing for ketonaemia and urgent assessment if a woman with Type 1 diabetes is unwell or hyperglycaemic. DKA is an extreme medical emergency carrying a fetal mortality rate of 10–30%.

4. Fetal Surveillance & Timing of Birth

• Ultrasound Schedule: Viability scan at 7–9 weeks; routine dating and first-trimester screening at 11–14 weeks; detailed 20-week anomaly scan including specialized four-chamber and outflow tract cardiac views; serial fetal growth ultrasound scans every 4 weeks (28, 32, and 36 weeks) to evaluate abdominal circumference and amniotic fluid volume (polyhydramnios).
• Timing and Mode of Birth: Elective birth (induction of labour or caesarean section) is offered between 37+0 and 38+6 weeks' gestation for women with Type 1 or Type 2 diabetes without other complications. Earlier delivery is indicated in the presence of fetal growth restriction, macrosomia, or pre-eclampsia.

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Maternal Cardiac Disease in Pregnancy

Cardiac disease remains the leading cause of indirect maternal mortality in the UK according to MBRRACE-UK. The profound haemodynamic demands of pregnancy—including a 45% increase in plasma volume, a 30% to 50% increase in cardiac output, and significant intrapartum autotransfusion—can trigger catastrophic cardiac failure in women with underlying structural, ischemic, or electrical heart disease.

1. Modified WHO (mWHO) Classification of Maternal Cardiovascular Risk

The European Society of Cardiology (ESC) and MBRRACE-UK endorse the Modified WHO (mWHO) classification, which stratifies maternal cardiovascular risk into four categories:

2. Clinical Red Flags in Maternal Cardiac Disease

Midwives must distinguish physiological pregnancy symptoms (mild exertional breathlessness, ankle oedema, systolic ejection murmur) from pathological cardiac decompensation. Red flag signs and symptoms that mandate urgent emergency escalation include:

• Breathlessness at rest or sudden-onset nocturnal dyspnoea.
• Orthopnoea (inability to sleep flat without extra pillows).
• Chest pain that is retrosternal, exertional, or radiating to the jaw/left arm.
• Palpitations accompanied by syncope, near-syncope, or presyncope.
• Persistent resting tachycardia (>100 bpm) or tachypnoea (respiratory rate >20 breaths/min).
• New pathological cardiac murmurs (especially any diastolic murmur or loud pansystolic murmur).
• Basal pulmonary crackles that do not clear with coughing, or elevated jugular venous pressure (JVP).

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Epilepsy in Pregnancy & Antiepileptic Pharmacology

Epilepsy is the most common serious neurological disorder in pregnancy. Uncontrolled tonic-clonic convulsions carry severe risks of maternal trauma, status epilepticus, fetal hypoxia, and intrauterine demise.

1. Teratogenic Risks & The Sodium Valproate Prohibition

• Sodium Valproate: Valproate carries a 10% risk of major congenital malformations (spina bifida, cardiac septal defects, cleft lip/palate, craniosynostosis) and up to a 30% to 40% risk of neurodevelopmental disorders, intellectual disability, and autism spectrum disorders. Under UK Medicines and Healthcare products Regulatory Agency (MHRA) regulations, sodium valproate is strictly contraindicated in women of childbearing potential unless the Pregnancy Prevention Programme (Prevent) is in place, and must not be used in pregnancy for epilepsy unless there is no suitable alternative. Since 2024, it must not be started in patients under 55 unless two specialists independently agree there is no other effective or tolerated treatment.
• Safer Alternatives: Lamotrigine and levetiracetam have the lowest established teratogenic profiles and are preferred monotherapies when clinically indicated.
• Folic Acid: All women with epilepsy taking any antiepileptic drug (AED) should take high-dose folic acid (5 mg daily) preconception until at least 12 weeks of gestation.

2. Gestational Pharmacokinetics & Drug Level Monitoring

During pregnancy, elevated hepatic enzyme activity, oestrogen-induced hepatic glucuronidation, and increased renal glomerular filtration accelerate the clearance of certain antiepileptics. Serum levels of lamotrigine can fall by 50% or more, predisposing the woman to breakthrough seizures. However, RCOG GTG68 advises that routine monitoring of antiepileptic drug levels in pregnancy is not recommended; levels may be checked in individual circumstances (for example, worsening seizure control on lamotrigine), with dose adjustment by the epilepsy team.

3. Intrapartum Management & Emergency Seizures

• Medication Adherence: Women must continue their prescribed oral antiepileptic medications throughout labour without interruption.
• Status Epilepticus vs. Eclampsia:
  • Any convulsion lasting >5 minutes, or repeated seizures without recovery of consciousness between episodes, represents status epilepticus.
  • Midwives must immediately differentiate epileptic convulsions from eclampsia. Eclampsia occurs in the context of pregnancy-induced hypertension (BP ≥140/90 mmHg), proteinuria, and hyperreflexia after 20 weeks' gestation, and is treated with magnesium sulfate, not standard antiepileptics.
  • First-line emergency medical treatment for an epileptic seizure lasting >5 minutes is intravenous lorazepam 4 mg (administered over 2 minutes) or buccal midazolam 10 mg, accompanied by high-flow oxygen (15 L/min via non-rebreather mask), left lateral tilt, and rapid multidisciplinary obstetric/anaesthetic escalation.

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Chronic Kidney Disease (CKD) & Systemic Lupus Erythematosus (SLE)

1. Chronic Kidney Disease

• Renal Thresholds in Pregnancy: Normal gestational vasodilation causes a 50% rise in GFR, lowering healthy maternal serum creatinine to 40–65 µmol/L. A serum creatinine >75 µmol/L is abnormal in pregnancy and denotes renal compromise.
• Obstetric Risks: CKD markedly increases the risk of superimposed pre-eclampsia (up to 40%), severe maternal hypertension, fetal growth restriction (FGR), and indicated preterm birth.
• Prophylaxis: CKD is a high-risk factor for pre-eclampsia, so NICE NG133 advises aspirin 75–150 mg daily from 12 weeks until birth (many units prescribe 150 mg at night).

2. Systemic Lupus Erythematosus (SLE) & Antiphospholipid Syndrome

• Disease Quiescence: Pregnancy should ideally be planned when SLE has been clinically quiescent for at least 6 months.
• Autoantibodies & Fetal Heart Block: Maternal anti-Ro (SSA) and anti-La (SSB) autoantibodies can cross the placenta and bind to fetal cardiac conduction tissue, triggering inflammation, fibrosis, and permanent congenital complete heart block (CCHB). Fetal heart rate must be monitored weekly or bi-weekly from 16 to 24 weeks' gestation using Doppler or specialized fetal echocardiography.
• Secondary Antiphospholipid Syndrome (APS): Characterised by lupus anticoagulant and anticardiolipin antibodies, predisposing to recurrent miscarriage, late fetal loss, and placental infarction. Managed antenatally with combination therapy: low-dose aspirin plus prophylactic low-molecular-weight heparin (LMWH).