Diagnosis and management of fetal malformations

Routine prenatal ultrasound anomaly screening program in a Nigerian university hospital: Redefining obstetrics practice in a developing African country

BACKGROUND

Congenital anomalies are among the leading causes of fetal and infant morbidity and mortality worldwide. Prenatal ultrasound (US) screening has become an essential part of antenatal care in the developed world. Such practice is just evolving in the developing countries such as Nigeria. The aim of this article is to present our initial experience and demonstrate the effectiveness of a prenatal US screening program in detecting congenital malformation in a developing country.

MATERIALS AND METHODS

This was a prospective evaluation of the prenatal US screenings conducted at a major referral hospital in Southwestern Nigeria. All pregnant women referred to the antenatal clinic for mid-trimester screening during the period of study were assessed.

RESULTS

Two hundred and eighty-seven pregnant women (5 with twin gestations) were presented for fetal anomaly scan during the study period. Twenty-nine anomalies (9.9%) were detected among the scanned population. Sixteen of the anomalies were followed to delivery/termination with a specificity of 93.5%. The commonest malformations were demonstrated in the genitourinary tract (34.5%) followed by malformations within the central nervous system (27.6%). Six (20.6%) of the anomalies were lethal. Five of the anomalies were surgically correctable.

CONCLUSION

Institutions and hospitals across Nigeria and other low- and middle-income countries need to develop policies and programs that would incorporate a standardized routine screening prenatal US in order to improve feto-maternal well-being and reduce the high perinatal mortality and morbidity in developing nations.

Techniques in current use in prenatal diagnosis

Prenatal diagnosis is now offered to the majority of pregnant women in Europe and the United States. Advances in obstetric and laboratory techniques mean that increasing numbers of conditions can be diagnosed prenatally; indeed, gene carriers can be identified before pregnancy in some cases. Current obstetric and laboratory techniques for prenatal screening and diagnosis of genetic disorders are discussed.

Routine radiographer screening for fetal abnormalities by ultrasound in an unselected low risk population

A screening programme for fetal abnormalities began at The Hillingdon Hospital in July 1986. Second trimester ultrasound scans are performed by radiographers. A combined prospective and retrospective study of the ultrasound findings and outcome in all pregnancies delivered in 1989-1990 was undertaken. 6412 babies were born during this period, of whom 6183 (96%) were examined by ultrasound in the second trimester; 29 pregnancies were terminated for fetal abnormality. Of the 89 fetuses who were abnormal at birth or at induced termination of the pregnancy (1.4%), 84 were scanned in the second trimester. In 51 cases the abnormality was detected before 22 weeks gestation (sensitivity, 60.7%). 56 of these 84 abnormal fetuses scanned had potentially lethal or major handicapping abnormalities of which 41 were detected by ultrasound before 22 weeks gestation (sensitivity, 73%). There was one false positive diagnosis of abnormality which did not affect outcome. 6352 babies were normal at delivery or on discharge from hospital (specificity, 99.98%).

Effectiveness of routine ultrasonography in detecting fetal structural abnormalities in a low risk population

OBJECTIVE

To review the efficacy of routine prenatal ultrasonography for detecting fetal structural abnormalities.

DESIGN

Retrospective study of the ultrasonographic findings and outcome of all pregnancies in women scanned in 1988-9.

SETTING

Maternity ultrasonography department of a district general hospital.

SUBJECTS

8785 fetuses.

MAIN OUTCOME MEASURES

Correlation of prenatal ultrasonographic findings with outcome in the neonate.

RESULTS

8733 babies were born during 1988-9, and 52 pregnancies were terminated after a fetal malformation was identified. 8432 (95%) of the fetuses were examined by ultrasonography in the second trimester. 130 fetuses (1.5%) were found to have an abnormality at birth or after termination of pregnancy, 125 of which had been examined in the second trimester. In 93 cases the abnormality was detected before 24 weeks (sensitivity 74.4%, 95% confidence interval to 66.7% to 82.1%. Two false positive diagnoses occurred, in both cases the pregnancies were not terminated and apparently normal infants were born. This gives a specificity of 99.98% (99.9% to 99.99%). The positive predictive value of ultrasonography in the second trimester was 97.9% (92.6% to 99.7%). Of the 125 abnormalities, 87 were lethal or severely disabling; 72 of the 87 were detected by the routine screening programme (sensitivity 82.8%, 73.2% to 90.0%).

CONCLUSION

Routine fetal examination by ultrasonography in a low risk population detects many fetal structural abnormalities but can present several dilemmas in counselling.