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Preventable Causes of Congenital Abnormalities
Dr Sue Page




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Preventable Causes of Congenital Abnormalities
Table of Contents
  • Diet / Vitamin
  • Medications
  • Infections
  • Recreational drugs
  • Maternal Conditions

    • Diet / Vitamin

    Folic Acid

    Probably the most widely publicised is the addition of folic acid to the diet 1 month preconception, and up to 16 weeks, to reduce the risk of Neural Tube Defects of all types. For couples with a previous NTD child, the reduction is 72%. Doses recommended are 0.5mg daily, or 5mg daily if the risk is judged high (eg. previous NTD, poor nutrition, anti-convulsant therapy)

    Vitamin A

    Vitamin A in doses greater than 1 mill IU is associated with birth defects

    Multivitamin

    Standard dose multivitamin use reduces the risk of facial clefts

    Calcium

    High dose calcium (2000mg daily) may be associated with lower maternal BP, and thereby less complications of pregnancy. Confirmatory studies are underway.

    Herbal

    Golden Seal increases uterine irritability and miscarriage

    Alkaloids such as in coltsfoot, groundsel, ragwort, and butterbur, have caused foetal ascites, hepatomegaly and stillbirth.

    Medications

    Many drugs cause adverse reactions in the foetus, but the following are of particular concern as they are common and teratagenic. The aim is to withdraw or reduce the treatment as far as possible prior to the month of conception. In, general, all medications should be avoided in pregnancy, and if unavoidable, restrained to category A types.

    Warfarin

    Warfarin has been asscociated with hypoplastic nasal structure & skeletal abnormalities

    Anti-convulsants

    Anti-convulsants have been asscociated with cleft lip & palate, congenital heart disease, CNS & skeletal abnormalities.

    Diazepam

    Diazepam has been asscociated with cleft palate.

    Tetracyclines

    Tetracyclines have been asscociated with stained teeth & depressed skeletal growth.

    Infections

    Rubella

    Rubella before 16 weeks crosses the placenta, resulting in severe defects esp. if 8-10 weeks, including heart abnormalities, mental retardation, deafness, and blindness. Preconception testing / vaccination should be offered to all women, with avoidance of pregnancy for 2-3 months after rubella vaccine is given.

    Syphilis

    Syphilis untreated after 16 weeks results in a variety of defects including CNS retardation, blindness, hypoplastic nose and limb deformities, anaemia, rashes. High risk women should be tested in both 1st and 3rd trimesters.

    Chickenpox

    Chickenpox can result in microcephaly, eye defects, limb hypoplasia, and miscarriage, for 2% of those who contract it before 20 weeks, and neonatal infection or stillbirth if acquired late in pregnancy. Immunoglobulin can be considered if significant exposure.

    Cytomegalovirus

    Cytomegalovirus is usually acquired in childhood, and is usually a mild illness, but can cause a fulminant infection including hepatitis. If the mother contracts it from a preschool age offspring, 10% of infants can be infected with microcephaly, deafness, cirrhosis, anaemia, pneumonia, and mental retardation.

    Toxoplasmosis

    Toxoplasmosis is not so common in Australia, and not routinely tested for, but women should be advised to avoid handling cat bowls or litter trays. It causes congenital hepatosplenomegaly, retinitis, and brain cysts with consequent retardation and epilepsy, and responds well to pyrimethamine and sulphonamide.

    Listeria

    Listeria is a bacterial infection found in soft cheese, cold deli meats, raw seafood It can cause miscarriage and stillbirth and these foods should be avoided.

    HIV

    HIV has a high rate of transmission to infant (20-50%), unless the mother opts for AZT in pregnancy, LSCS, bottle feeding and infant AZT for 6 weeks (down to 3%).

    Recreational drugs

    Caffeine

    Evidence for this is conflicting, but some reports suggest that 8 cups or more may be associated with reduced female fertility and increased rates of miscarriage, premature delivery, and stillbirth.

    Alcohol

    International reports usually link foetal alcohol syndrome (mental & growth retardation, "portwine stain" birthmarks, and facial deformities) to maternal ingestion of 8 or more standard drinks per day, but it has also been reported at levels of 10 drinks per week. There is no clear knowledge pertaining to safe levels, esp. in the first 8 weeks, but 1-2 drinks and not every day is thought to be safe. Alcohol has also been linked to reduced quantity and quality of sperm.

    Cocaine

    Cocaine use in first trimester results in higher rates of spontaneous abortion, and in surviving foetuses it has been associated with kidney defects and placental abruption.

    Marijuana

    Marijuana reduces sperm counts, and results in disturbed sleep patterns in children through to 3 years old. (Arch. Paed. & Adolescent Medicine, 1995)

    Heroin

    Heroin has no specific defect syndrome, but exposes the mother to a variety of infectious diseases, including hepatitis and endocarditis, and a 59% risk of antenatal complication (usually prem. labour +/- chorioamnionitis)

    Petrol sniffing

    Petrol sniffing causes neurodevelopment impairments, including spastic quadriplegia.

    Smoking in Pregnancy

    Smoking is the single most important preventable cause of perinatal morbidity and mortality in our community. The evidence linking smoking to IUGR is sufficent that the US centre for Health Promotion and Education has been using the term "fetal tobacco syndrome" since 1995, while the first randomised prospective study to demonstrate that a reduction in smoking improves infant birthweight was published by Sexton & Hebel in 1984. Rates of smoking are higher in women of low socioeconomic class, but are approx. 25-30% overall. A recent Australian study found that while women could successfully modify alcohol consumption, 40% of smokers were unable to modify their tobacco intake, and 10% actually smoked more! Smoking also reduces sperm counts, and increases the incidence of resp. illnesses and SIDS in the infant.

    Generally speaking, the more intensive the intervention the greater the smoking cessation rate; but obviously this is limited not only by the motivation of the mother, but also by the motivation and skills of the health worker and by the consultation time available. It therefore becomes necessary to know which methods are cost and time effective:

    Smoking Counselling in Pregnancy
    (1) Brief Advice (1-2 mins)
    • 5% long term cessation rate
    • up to 10% if lighter smoker, primip, pregnancy-related symptoms
      (2) Medium Behavioural Intervention (5-10 mins+follow-up)
    • 10% long term cessation rate
    • 15%public clinics, 25% private clinics (Windsor & Orleans, 1986)  
      • check knowledge and challenge misconceptions (eg.small babies are good)
      • provide information tailored to the individual mother,
      • address specific fears eg. nicotine withdrawl,weight gain, and coping with stress
      • encourage alternative behaviours tailored to the individual
      (3) Intensive Behavioural Intervention (>10 mins, >2 follow-up sessions)
    • 22.5 long term cessation rate and at 3 yr follow-up 36%still abstaining vs 8% in the control group (Richmond et al)
    • in addition to counselling, the use of written reminders, home visits and self-help manuals
    • incorporating health information and physiologic testseg. height/weight, lung function tests, U/S with specific verbal & visual feedback (Reading et al)
    • serum cotinine/carboxyhaemoglobin
      (4) Smoking Cessation Clinics
    • 15-50% long term cessation rates
      • really only suitable for the highly motivated, willing to commit 4-9 hours
      • studies show those referred antenatally rarely actuallyattend
    women may find self-help approaches more acceptable
     

    Maternal Conditions

    A number of maternal conditions affect foetal development, but perhaps the most significant of these is diabetes.

    Diabetes

    The incidence of diabetes prior to conception is 0.2-0.3% (usually IDDM), with a further 2-3% developing impaired glucose tolerance of pregnancy (gestational diabetes). Even with specialist care the perinatal mortality of a pregnancy complicated by diabetes is 2-3 times that of a normal pregnancy.

    Macrosomia occurs in up to 50% of diabetic pregnancies and increases infant mortality by 3 times, morbidity by 8 times, while 50% will be delivered by LSCS due to CPD and failure to progress. Macrosomia is not excluded by tight diabetic control, and needs U/S review at 36-39 weeks.

    Other risks include:

    Maternal:

    1. Polyhydramnios, 6-25% (13% deliver prematurely)
    2. PIH and Proteinuria, up to 25%
    3. Severe oedema requiring hospitalisation, 10-20%
    4. Abruptio, 5%
    5. Pyelonephritis, 1.5-12%
    Infant:

    1. Anomalies (cardiac, NTD, skeletal incl. sacral agenesis), 5-8%
    2. Intrauterine death
    3. Perinatal mortality 3 times normal, 50% due to anomalies
    4. Respiratory Distress Syndrome, up to 50%
    5. Neonatal hypoglycaemia, 50%
    6. Polycythemia 33%, Jaundice 16%
    7. Hypocalcaemia
    If HbA1c is above 6 at 6 weeks, the risk of abnormality is high. Ideally HbA1c should be below 6 for 3 consecutive months prior to ceasing contraception.

    The Australian Diabetes in Pregnancy Study Group recommends screening of all gravidae at 26-28 weeks by 75g glucose load. If BSL is >8.0 at 1 hour a full GTT should then be performed. If the 2 hour level is then >8.0 this is diagnostic.

    The diet should aim for 50% carbohydrate, 30% unsaturated fats, 20% protein; with 100-120 kj / kg ideal.

    Less than 3% of diabetic pregnancies require insulin.

    Dr Sue Page
    General Practioner
    Lennox Head
    NSW
    Australia 2477
    cmitchell@om.com.au

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    It was originally posted on 12/4/98; 8:40:48 AM.
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