Margaret B. McNay

Gastroschisis and exomphalos: precise diagnosis by midpregnancy ultrasound

Summary. As part of a regional screening programme for neural‐tube defects the cause of the raised α‐fetoprotein levels was correctly identified in 13 pregnancies with a fetal abdominal wall defect by the 22nd week. Careful ultrasound study identified gastroschisis in seven fetuses and exomphalos in six: the presence or absence of a sac, the course of the umbilical vessels and the abdominal organs involved were the most important diagnostic criteria. Pregnancy continued into the third trimester in five cases complicated solely by gastroschisis and two babies have survived the neonatal period following surgical correction. It is suggested that precise identification by ultrasound of the type and severity of abdominal wall defect and also of the presence or absence of associated anomalies will enable the selection of some babies with gastroschisis or isolated exomphalos which have a good prognosis for survival without handicap.

Atrial-Natriuretic-Peptide - A Vasodilator of the Fetoplacental Circulation

Paired maternal and fetal atrial natriuretic peptide concentrations were measured in 62 percutaneous umbilical blood samplings performed principally for the assessment and treatment of rhesus isoimmunization. Pretransfusion fetal atrial natriuretic peptide levels were significantly higher than maternal atrial natriuretic peptide levels (median 117 pg/ml vs median 32 pg/ml; p less than 0.001); paired pretransfusion fetal and maternal atrial natriuretic peptide samples showed a weak correlation with each other (R2 = 17%; p = 0.002). Fetal atrial natriuretic peptide levels correlated inversely with hematocrit (R2 = 14%; p = 0.003), but not with albumin or gestational age. Paired pretransfusion and posttransfusion (median = 134 pg/ml) fetal atrial natriuretic peptide levels (n = 38) showed a significant rise after transfusion (p less than 0.001); this rise was related to the percentage of fetoplacental blood volume transfused (R2 = 33%; p = 0.035). In a subgroup of 26 procedures, change in fetal atrial natriuretic peptide levels was weakly correlated with transient reductions in the Doppler systolic/diastolic ratio of the umbilical artery (R2 = 14%; p = 0.07). These data support work in animals that indicate a role for atrial natriuretic peptide in the human fetus, but these data do not confirm that atrial natriuretic peptide modulates fetoplacental vascular impedance in the human fetus.

FERRTTIN AS AN ASSESSMENT OF IRON STORES IN NORMAL PREGNANCY

In Glasgow, the iron stores in healthy women and in normal pregnant women on prophylactic iron supplementation have been assessed by measurement of plasma ferritin. Ferritin concentration fell progressively to a low level in late pregnancy suggesting that the average iron store was inadequate to meet the demands of pregnancy and that dietary iron supplements were therefore required. There was no evidence that iron supplementation led to excessive iron stores.

Midtrimester chorionic villus sampling: An alternative approach?

OBJECTIVE Our purpose was to audit midtrimester chorionic villus sampling after a positive maternal serum screening test for autosomal trisomy. STUDY DESIGN From January 1990 until July 1993 chorionic villus sampling was offered to all screened positive women. RESULTS Five hundred fifty-one mothers had chorionic villus sampling. The mean age was 31.7 years. The mean gestational age was 18.2 weeks. The mean time for direct karyotyping was 4.4 days and for culture results 20.2 days. Results were obtained in 99.6% of samples: direct plus culture results in 94%, direct results alone in 2.3%, and culture results alone in 3.3%. Fourteen pregnancies had abnormal karyotypes. There were five cases of placental mosaicism and one false-positive result. The loss rate was 0.4%. CONCLUSION Midtrimester chorionic villus sampling, which is easier to perform than cordocentesis, provides a rapid and reliable karyotype. The complication rate is comparable to that of other invasive procedures.