The majority of pregnancies are not complicated by underlying disease; however, there are a number of conditions that can affect both mother and unborn baby. Care for these women is important both before conception and throughout their pregnancy in order manage the risks to ensure they remain as low as possible. When women with underlying conditions become pregnant they are often seen in a joint clinic with an obstetrian and a specialist physician.
This article will discuss some of the more prevalent conditions that affect pregnancy (noted above) but will focus particularly on diabetes, epilepsy and heart disease, because of their clinical importance.
N.B: Neonates born to diabetic mothers are usually kept on the Special Care Baby Unit for 24-48 hours in order to monitor for hypoglycaemia.
Epilepsy affects 0.5-1% of women of child-bearing age. The main challenge with epilepsy in pregnancy is weighing up the risk of continuing anti-epileptic medication (many of which are teratogenic) versus the consequences of stopping the medication and the threat of increased fits (which may result maternal and fetal hypoxia). It is generally considered that uncontrolled seizures are more harmful to the fetus than the potential teratogenic effects of anti-epileptic medication (about 2% risk).
Pre-pregnancy counselling is important to convey this to the patient but ultimately, it is the patient’s decision.
Other pregnancy complications that have been associated with epilepsy include:
- Pre-term delivery
- Low birth weight
- Fetal risk of epilepsy (3%)
N.B: Warfarin is associated with an increased risk of congenital malformations if taken in the first trimester and placental and fetal haemorrhage if taken in third trimester.
- Avoid ACE-inhibitors (risk of adversely affecting fetal BP, damage to fetal renal function, skull defects and oligohydramnios)
- First line anti-hypertensive in pregnancy is methyldopa
- Admit for bedrest if hypertension is severe
- Careful monitoring for fetal growth restriction throughout pregnancy
- CTG monitoring throughout labour
- Ideal: vaginal delivery but low threshold for caesarean section
- Magnesium sulphate administered if risk of eclampsia
- BP will usually drop to pre-pregnancy levels following delivery but need to monitor mother for 48hr for eclampsia
- Affects 0.2% of pregnancies
- Maternal risks: cardiac arrhymias, diarrhoea, vomiting, abdominal pains, psychosis
- Fetal risks: growth restriction, stillbirth, tachycardia, premature delivery, if mother has autoimmune hyperthyroid autoantibodies can cross the placenta causing fetal thyrotoxicosis and goitre
- Management: treat with lowest possible dose of propylthiouracil (does cross the placenta, occasionally causing fetal hypothyroidism but less than carbimazole)
- Radioactive iodine is contraindicated in pregnancy (it destroys the fetal thyroid gland)
- Affects 1% of pregnant women
- Thyroid function tests need to be performed 6-weekly throughout pregnancy to ensure optimum treatment with thyroxine
- Maternal risks: post-natal depression, higher risk of pre-eclampsia
- Fetal risk: cretinism (severe physical and mental developmental delay due to congenital hypothyroidism)
- Common in pregnancy and usually does not cause any problems
- Asthma medications are safe to use during pregnancy
- If asthma is poorly controlled there is a higher risk of fetal growth restriction
- Avoid general anaesthesia in labour, ergometrine and NSAIDs, as they are all associated with bronchospasm#
Ideally women should be on as few (and preferably no) medications throughout pregnancy. This is because the effects of most medications on pregnancy are unknown as clinical trials are restricted in pregnant women. However the following medications should be avoided completely in pregnancy if at all possible:
- Lithium (bipolar disease)
- Isotretinoin (acne)
- Some antibiotics (tetracycline, doxycycline and streptomycin)
- Methotrexate (chemotherapy agent/antimetabolite)
Nevertheless it is important to weigh up the risk: benefit ratio. In some cases the risk of stopping the medication is higher than the potential risk of taking it throughout pregnancy. As always it is important to consider each case individually.
Impey L, Child T. Obstetrics and Gynaecology. 3rd edition. Wiley-Blackwell; 2008. pp. 165-185
Campbell S, Lees C. Obstetrics by Ten Teachers. 17th edition. New York: Oxford University Press; 2000. pp. 141-161
British National Formulary. 58th Edition, London; BMJ Group and RPS Publishing 2009, September 2009. pp. 831-851.
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