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Biomedical subjects

N A Callan

Publications and source records attributed to N A Callan.

At least 19 recordsLinked to original sources
PubMed2000

Prediction of birth weight by ultrasound in the third trimester.

OBJECTIVE: To compare the accuracy of predicted birth weight by the gestation-adjusted projection method using ultrasonographic measurements obtained just before and at term. METHODS: The study group comprised patients with singleton pregnancies who underwent sonograms between 34.0 and 36.9 weeks' gestation (period 1) and at 37 weeks and beyond (period 2). The mean error in birth weight prediction, absolute birth weight error, and signed and absolute percent errors were compared with paired t tests. Thus, each patient served as her own control. RESULTS: The study included 138 patients undergoing 276 sonograms. The mean absolute error of the predicted birth weight was smaller for period 1 than for period 2 (197 +/- 167 g compared with 235 +/- 209 g, P =.019). The mean absolute percent error was 6.2 +/- 5.2% for period 1 compared with 7.4 +/- 6.3% for period 2 (P =.019). These same trends were observed when fetuses with suspected growth abnormalities were examined separately. Averaging data from both gestational periods did not improve the prediction of birth weight. CONCLUSION: Sonograms between 34.0 and 36. 9 weeks' gestation allow for more accurate prediction of birth weight than sonograms later in gestation. Though these differences are small and not clinically significant, this study indicates that serial sonograms in the late third trimester do not improve the ability to predict birth weight, even in abnormally grown fetuses. A single sonogram between 34 and 37 weeks' gestation is recommended for prediction of birth weight.

Adolescent↗
PubMed1996

Adjustment of birth weight standards for maternal and infant characteristics improves the prediction of outcome in the small-for-gestational-age infant.

OBJECTIVE: Birth weight is a function of gestational age. Various maternal and infant characteristics also affect birth weight. This study sought to adjust for these factors to better define abnormal growth. STUDY DESIGN: Maternal and infant characteristics from normal pregnancies were correlated with birth weight. A formula was developed and applied to a second group in which we compared perinatal outcomes in normally grown infants with those who were small for gestational age. We compared outcomes between small-for-gestational-age infants defined by the formula with those defined by conventional tables. RESULTS: Infants defined by the formula as small-for-gestational-age were more likely to have morbidity and mortality than those who were normally grown (p < 0.001). Small-for-gestational-age infants defined by the formula had more deaths and adverse outcomes than those defined by gestational age. CONCLUSION: Adjusting birth weight standards for maternal and infant characteristics may improve the prediction of adverse outcomes.

Adult↗
PubMed1996

The role of HLA antibodies in neonatal thrombocytopenia: a prospective study.

The role of HLA antibodies in neonatal alloimmune thrombocytopenia is controversial. We prospectively studied the sera of obstetric patients at delivery for HLA antibodies and correlated their presence with umbilical cord blood platelet counts. We studied 493 births at The Johns Hopkins Hospital comprising of 357 African American, 115 Caucasian, and 21 babies of other racial groups. One hundred and thirty nine mothers had HLA antibodies. Of these HLA alloimmunized mothers, only ten infants had platelet counts of 150,000/ microL or less. Three hundred and eight mothers with no detectable antibodies gave birth to 27 infants with platelet counts of 150,000/microL or less. Yates corrected Chi square analysis showed no significant relationship between maternal HLA alloimmunization and baby platelet count (p = 0.709). Only 8 of sixty cord sera from babies of HLA alloimmunized mothers were positive for HLA antibodies. The HLA cord blood antibody results were then correlated with the neonatal platelet counts. The Fisher's exact test showed no significant relationship between the presence of HLA antibodies in cord blood samples and neonatal platelet counts (p = 0.232). Although one third (31%) of mothers have HLA antibodies, neonatal thrombocytopenia is rarely associated with this finding. However, HLA antibodies can cross the placenta, and in these unusual cases, may be associated with a higher risk of neonatal thrombocytopenia.

Female↗
PubMed1995

Molecular genotyping of fetal platelet antigens with uncultured amniocytes.

OBJECTIVE: Amino acid substitutions in platelet membrane glycoproteins result in alloantigens implicated in neonatal alloimmune thrombocytopenia. We report the use of the reverse dot blot technique to genotype the five major fetal platelet alloantigens from amniotic fluid cells. STUDY DESIGN: We evaluated a patient with Bakb platelet antibodies who had a previous pregnancy complicated by fetal intracranial hemorrhage. The father was heterozygous Baka/Bakb, giving the pregnancy a 50% risk for platelet incompatibility between mother and fetus. Amniotic fluid was obtained at 16 weeks. Deoxyribonuleic acid was extracted from uncultured amniocytes and amplified with polymerase chain reaction. These products were hybridized to filters containing oligonucleotides specific for each of the 10 different platelet antigen alleles. Reactivity was detected with a chromogenic substrate. RESULTS: The reverse dot blot genotyping of uncultured amniocytes revealed the fetus to be Baka/Baka, thus not at risk for neonatal alloimmune thrombocytopenia. CONCLUSION: Precise knowledge of fetal platelet type by amniocentesis could obviate the need for fetal blood sampling and significantly alter prenatal management of neonatal alloimmune thrombocytopenia.

Adult↗
PubMed1994

Neonatal lupus erythematosus. Report of serological and immunogenetic studies in twins discordant for congenital heart block.

Autoantibody, HLA studies and C4 phenotypes were performed on twins discordant for isolated congenital heart block. Serum from the mother and cord blood from the infants revealed Ro(SSA) and La(SSB) antibodies in all three sera. No significant difference in Ro(SSA) antibody titre was noted in the cord blood of either twin when compared with maternal titres, as detected by a sensitive ELISA assay. The infants' mother was HLA-DR3 positive. Both infants had identical HLA and C4 phenotypes. Immunoblot analysis revealed that sera from both mother and infants reacted with the 52-kDa Ro(SSA) macromolecule. Quantitative cord blood IgM levels were not elevated in either twin. This study indicates that placental transfer of anti-Ro(SSA) or anti-La(SSB) alone to the fetus is not sufficient for the expression of congenital complete heart block. We conclude from this experiment of Nature that there must be a second event determining which infant develops complete heart block, but this is unknown at present.

Adult↗
PubMed1993

Effect of fetal movement on the amniotic fluid index.

OBJECTIVES: Fetal movement has been shown to change the size and location of amniotic fluid pockets during measurement of the amniotic fluid index. The effect of redistributing the fixed intrauterine fluid volume on the amniotic fluid index is unknown. Therefore we tested the hypothesis that the amniotic fluid index was unaffected by fetal movement. STUDY DESIGN: A single examiner prospectively determined the amniotic fluid index before and after three discrete episodes of fetal movement during 96 biophysical profiles. A reliable blinded examiner provided a second postmovement measurement as a control. Data were analyzed by the paired t test. RESULTS: The mean change in the amniotic fluid index after fetal movement was 1.5 +/- 0.1 cm and 2.5 +/- 0.2 cm for postmovement determinations by the same examiner and blinded observer, respectively (p < 0.001). CONCLUSION: Interobserver and intraobserver variation can account for the change in the amniotic fluid index after fetal movement.

Amniotic Fluid↗
PubMed1993

Congenital heart disease in adolescents and adults. Pregnancy and contraception.

As the detection and treatment of congenital heart disease improves, more women are reaching childbearing age. The type of congenital heart disease, whether there has been corrective surgery, and the patient's functional status determines the maternal as well as fetal outcome. The patient may present to her physician for preconceptual counseling or late in her pregnancy with little care and in severe distress. These possible situations necessitate that the physician becomes familiar with congenital heart disease and its implications in the pregnant patient.

Contraception↗
PubMed1993

Prenatal diagnosis of congenital heart disease.

In counseling the patient with a fetus with CHD, attempts should be made to determine the exact cardiac diagnosis and whether there are associated extracardiac or chromosomal abnormalities. A careful family history and examination of appropriate family members may lead to the diagnosis of a genetic syndrome. An evaluation of the maternal medical and obstetric history will explore the possibility of maternal disease states, teratogens, or environmental exposures as cause for the cardiac lesion. The information obtained from a prenatal evaluation may lead to a possible cause of CHD in the fetus and thus more accurate counseling regarding recurrence risks and the prognosis for the present pregnancy. With further improvement in the prenatal diagnosis of structural cardiac disease, a knowledge of possible causes is essential for the clinician providing counseling. In addition, a multidisciplinary approach with the involvement of obstetricians, neonatologists, pediatric cardiologists, cardiac surgeons, and geneticists will optimize care in pregnancies complicated by a fetus with structural heart disease.

Echocardiography↗
PubMed1991

Prenatal diagnosis of tetralogy of Fallot with absent pulmonary valve.

Multiple indications for fetal echocardiography have been proposed that includes polyhydramnios. In this report, the prenatal diagnosis of tetralogy of Fallot with absent pulmonary valve and absent ductus arteriosus was made in a patient presenting with polyhydramnios. Tracheobronchial and esophageal compression secondary to gross dilation of the pulmonary artery is considered the etiology of the polyhydramnios, and in the case of this structural defect is an indicator of poor prognosis.

Adult↗
PubMed1991

Fetal echocardiography: indications for referral, prenatal diagnoses, and outcomes.

Three hundred three fetuses were studied with fetal echocardiography and 21 were diagnosed with congenital heart disease (CHD). Indications for study, prenatal findings, and postnatal outcomes were examined in all fetuses studied. The most common indications for referral were previous family history and fetal dysrhythmia. Of 189 fetuses studied for these indications, six had CHD. Indications with the highest proportion of abnormal studies included an abnormal four-chamber view of the heart (50% abnormal), fetal hydrops (30.8% abnormal), and polyhydramnios (25% abnormal). Five of 21 with CHD had chromosomal defects and eight had extracardiac anomalies. Two of the 21 fetuses with CHD survived. Present referral indications led to the diagnosis of the most severe lesions, yet reassurance is provided to many couples with normal fetuses. Fetal echocardiography is important in the care of the fetus at risk for CHD.

Echocardiography↗
PubMed1991

Stuck twin with cotwin nonimmune hydrops: successful treatment by amniocentesis.

Until the recent introduction of therapeutic amniocentesis, pregnancies complicated by the stuck twin phenomenon usually suffered poor outcomes. We report the first case in which a single amniocentesis of the cotwin was followed by equalization of amniotic fluid volume in both sacs, resolution of nonimmune hydrops in the cotwin, and delivery of 2 healthy infants. The cause of the phenomenon in this was most likely severe twin-twin transfusion, based on a negative hematologic and serologic immune and nonimmune hydrops evaluation, and placental histology revealing a superficial large-caliber arteriovenous anastomosis joining the twins' circulations without an intervening capillary bed. The mechanism proposed for the physiologic response in this case to therapeutic amniocentesis is based on the correction of abnormal amniotic fluid volumes and pressures. This contention is supported by histologic evaluation of the placenta and the intrapartum fetal heart rate tracing.

Adult↗
PubMed1991

Fetal echocardiography.

Fetal echocardiography is an essential technique in the evaluation and management of fetal disease. Recent reviews address the accuracy of the technique, the benefit of routine screening, the association with chromosomal defects, and outcomes in fetuses with the prenatal diagnosis of congenital heart disease. Advances in Doppler have resulted in the more accurate and rapid diagnosis of structural heart disease, and in the use of this technique in the physiological assessment of fetal disease states.

Arrhythmias, Cardiac↗
PubMed1990

Intrauterine growth retardation: characteristics, risk factors and gestational age.

Maternal, obstetrical, and neonatal factors were studied in 1604 pregnancies complicated by intrauterine growth retardation and 1604 non-IUGR controls. These were examined in the overall IUGR group and at various gestational ages. Eighty-six percent of perinatal deaths were found in the IUGR group with 57.4% occurring prior to labor. Maternal smoking, low weight gain, low prepregnancy weight, and hypertension were found more frequently in the IUGR population. In addition, maternal hypertension was found to be significant in the IUGR infants delivered prematurely.

Adult↗
PubMed1990

Fetal genitourinary tract anomalies: evaluation, operative correction, and follow-up.

The prenatal diagnosis of a genitourinary anomaly was made in 53 fetuses. Sonographic findings, antenatal course, and postnatal treatment and outcomes were examined. No interventional therapy was undertaken in utero, and the natural history could be examined in the 44 of 53 (83%) who did not electively terminate their pregnancies. Twenty-three of the total 53 (43%) had unilateral disease and 30 (57%) had bilateral involvement. Thirty-five of 53 (66%) survived, with 22 undergoing operative therapy postnatally. In all but one of the 35 survivors, the anomaly was isolated to the genitourinary tract, and the majority of surviving fetuses had unilateral disease. Oligohydramnios was present in only three of 35 survivors, and none had severe oligohydramnios. Nine of 53 women underwent termination of pregnancy and nine others experienced a neonatal death. All 18 of their fetuses had bilateral disease, with oligohydramnios present in 14 (78%). All five fetuses with chromosomal abnormalities were found in this group of 18. The majority of fetuses with a genitourinary anomaly will do well postnatally. Pulmonary hypoplasia, extrarenal anomalies, and chromosomal defects are frequent findings in the minority with poor outcomes. A multidisciplinary approach to management of the pregnancy with a fetal genitourinary tract anomaly is essential to optimize outcome.

Abortion, Eugenic↗
PubMed1987

Ultrasonic ratio of fetal thoracic to abdominal circumference: an association with fetal pulmonary hypoplasia.

Real time ultrasound was used in pregnant women who were considered to be at risk for development of pulmonary hypoplasia (n = 26). The population consisted of women who had either premature rupture of membranes (n = 16) or oligohydramnios (n = 10). The ratio calculated by comparing the fetal thoracic circumference to abdominal circumference was obtained in all cases within 10 days of delivery. This ratio correlated strongly with neonatal outcome. Multivariate regression models of neonatal outcome were developed to analyze the relationship of gestational age at which premature membrane rupture occurred, the duration of premature rupture, date of birth, and prenatal diagnosis. The addition of the thoracic circumference to the abdominal circumference ratio increased significantly the proportion of explained variability. Application of this ratio should be considered in evaluating fetal status in oligohydramnios and in the expectant management of premature rupture of membranes.

Amniotic Fluid↗