Tuesday, 17 November 2009

Cystic fibrosis in Pregnancy

This is a multisystem disorder with impaired cellular secretion.
Commonest autosomal recessive disorder in U.K.
In Carrier rate 1:25 in Caucasians.In USA 1:30 American is a symptomless carrier.

Most common single mutation in Nonhispanic Caucasians is deltaF508.This occurs in approximately 65-70% of cases.DNA probes exist to detect 95% of mutations.If the couple already had a affected child,the defective gene could be identified and then prenatal diagnosis can be done to exclude cystic fibrosis.



Clinical features
1.recurrent lung infection/bronchiectasis/respiratory failure

2.pancreatic deficiency-malnutrition & diabetes.


Effect of Cystic fibrosis in Pregnancy
Fertility
Female: Fertility is reduced due to 1.thick cervical mucous 2.low lean body mass 3. voluntary infertility due to fear of producing affected children.

Male:
Most are infertile due to atresia of the vas & epididymis.

Pre pregnancy counselling

Factors to consider

1.cor pulmonlae

2.uncontrollable recurrent respiratory tract infection.

3.vital capacity - Patients with vital capacity less than 50% recommended termination.Many cystic fibrosis patients and patients with kyphosis with such vital capacity have normal pregnancy.

4.Right ventricular cavity size at end diastole is a good prognosticator of clinical outcome.

5.Patients may have diabetes and/or liver disease.Screening for diabetes need to be done.

6.Presence of Burkholderia cepacia is also an important risk factor.
Women's life span is reduced,so implications for parenting should be discussed.


Contraindication to pregnancy

1.Pulmonary hypertension
2.Cor pulmonale
3.FEV1 <30-40 class="ii gt">
Genetics
If father is a carrier-50% of babies wold be born with cystic fibrosis,other 50% would be carriers.

If father's carrier status unknown, the risk of CF baby is 2-2.5% as the carrier status is UK general population is 1:25.

Antenatal
1.risk of spontaneous abortion not increased.
2.complication in pregnancy
(A)prematurity
(B)IUGR-due to chronic hypoxia


Principles of antenatal management

1.antenatal screening- Power point on Cystic Fibrosis screening
2.support maternal nutrition
3.regular physio therapy
4.prevention & early treatment of infections.
5.avoid prolonged hypoxia
6.regular growth monitoring-Growth restriction can be managed by bed rest, nutritional supplements & oxygen.


Antibiotic treatment


Generally risk of infection is greater than the side effects of antibiotics.
Penicillin,cephalosporins and erythromycin are safe in pregnancy.
Tetracycline should be avoided.
Monitoring of drug levels should be done when intravenous aminoglycosides are used.
Data on new drugs like imipenam is limited.



The patient is managed by joined care between cystic fibrosis center & specialized obstetric center.


Screen for diabetes mellitus around 20 weeks


Presence of resting hypoxia(oxygen saturation 80-90%) is an indication for admission for bed rest & oxygen therapy.







Intrapartum


1.care with fluid & electrolyte as patients may easily become hyponatraemic & fluid overload should be avoided in corpulmonle.

2. epidural or caudal anaesthesia is preferred as there is risk post anaesthetic atelectasis.

3.risk of pneumothorax- be wary of chest pain

4.instrumental delivery could be used avoid prolonged second stage.


Postpartum
Breast feeding isn't contraindicated.Sodium & protein content of breast milk is normal.

Most medications used in the management of cystic fibrosis are safe in pregnancy.


Effect of pregnancy on disease

Pregnancy didn't affect the rate of annual decline in FEV1.



Sources
1.Nelson-Piercy C. Handbook of Obstetric Medicine, Second Edition. 2nd ed. Taylor & Francis; 2001.


2.Swiet MD. Medical Disorders in Obstetric Practice. 4th ed. Wiley-Blackwell; 2002.




Other sources



Article from Chest Journal

Another article