Carrier screening for cystic fibrosis: a perinatal perspective

Advances in preconception genetic counseling

Preconception counseling offers couples contemplating pregnancy the opportunity to identify and reduce potential pregnancy risks, plan care for known risks, and establish early prenatal care. The goal of preconception counseling is to promote physically and emotionally healthy parents in an attempt to ensure optimal prenatal, intrapartum, and postpartum maternal and fetal health. The advantages of addressing these issues prior to conception include the opportunity of giving recurrence or occurrence risk information for informed decision regarding pregnancy, the accessibility of more reproductive options such as preimplantation genetic diagnosis, and the opportunity to make lifestyle, medical, and behavior alterations for optimal maternal and fetal outcome. This article will discuss advances and updates in preconception genetic counseling including risk assessment and potential intervention for concerns identified through evaluation of family history, ethnicity, maternal age, medical and obstetric history, and associated psychosocial and nursing implications. Significant advances have emerged in the areas of cystic fibrosis carrier screening, first trimester screening, preimplantation genetic diagnosis, and detection and treatment of maternal thrombophilia.

Metabolic risk factors for stone formation in patients with cystic fibrosis

PURPOSE

Cystic fibrosis is characterized by chronic pulmonary disease, insufficient pancreatic and digestive function, and abnormal sweat concentrations. Patients with cystic fibrosis also have an increased incidence of nephrolithiasis. We compared the results of metabolic evaluation in patients with cystic fibrosis with and without nephrolithiasis.

MATERIALS AND METHODS

A total of 496 patients were evaluated at our center, including 98 with a mean age of 25 years who had cystic fibrosis and complete metabolic evaluation available between 1996 and 2000. Of these patients 13 (13%) had a history of nephrolithiasis. The records were reviewed for clinical characteristics and all patients underwent metabolic evaluation, including serum electrolyte measurement and 24-hour urine collection. Statistical analysis was done to compare the stone versus nonstone groups.

RESULTS

The incidence of nephrolithiasis in our study was 3%. We identified 13 patients 16 to 41 years old (mean age 27) with nephrolithiasis, of whom 62% had had multiple episodes. Flank pain was the presenting symptom in 9 of the 13 cases (69%). Renal ultrasound and computerized tomography were the most common imaging modalities. In 9 cases stones were passed without intervention, extracorporeal shock wave lithotripsy was required in 2 and ureteroscopy with stone extraction was done in 2. Calcium oxalate was the dominant stone composition in the 9 patients in whom stone analysis was performed. Metabolic evaluation of the stone versus no stone groups showed elevated urinary oxalate (45.5 versus 42.5 mg./24 hours), relative calcium oxalate supersaturation (5.3 versus 7.2) and decreased urinary citrate in the 2 groups. There was a statistical difference in citrate excretion with lower levels in stone formers (102 versus 218 mg./24 hours, p = 0.0007).

CONCLUSIONS

Patients with cystic fibrosis have an increased incidence of nephrolithiasis and are at high risk for recurrence. Metabolic evaluation is indicated in all patients with cystic fibrosis and urolithiasis since most have hyperoxaluria, urinary calcium oxalate supersaturation and decreased urinary citrate. Correcting detected stone risk factors in these cases may decrease stone recurrence.