Ultrasound identification assists in determining chorionicity in twins, in the interpretation of sex chromosome mosaicism and aneuploidy and in sex-linked conditions presenting after 14 weeks. This study addresses the frequency and accuracy of gender identification in a series of consecutive patients presenting for amniocentesis for genetic indications. Amniocentesis was performed at 14-20 weeks in 843 fetuses over a 5-year period. Ultrasound prediction of fetal gender was documented in 93.3% (770/843). The overall accuracy of diagnosis of fetal gender was 99.3% (765/770). Errors in diagnosis of gender were more likely to occur in the assessment of the female fetus. Such errors in diagnosis may be minimized by combining both tangential/transverse and sagittal views of the fetal perineum.

Summary Spontaneous fetomaternal haemorrhage at 14 to 20 weeks gestation resulted in raised serum alpha‐fetoprotein (AFP) levels in 13 of 150 patients attending a genetic counselling clinic. In all 13 patients, the placenta was anterior or fundal in position. By allowing for a rise in serum AFP levels of 4 μg/l for each fetal cell seen in 30 high power fields (Kleihauer test), a 62·5 per cent reduction in the number of patients selected for amniocentesis because of raised serum AFP levels would have been achieved. The occurrence of fetomaternal haemorrhages at the time of amniocentesis can be detected by either the Kleihauer technique or the measurement of maternal serum AFP levels.

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Prenatal diagnosis of the Meckel syndrome was made at 20 weeks of gestation from the findings of a biparietal diameter smaller than expected for gestational age, a grossly raised amniotic fluid alphafetoprotein level and a rapid growth of foetal macrophages after 20 hours culture. Termination at 23 weeks of gestation resulted in a male foetus with an occipital encephalocele, microcephaly, Polydactyly, and bilateral polycystic kidneys. This case report emphasises the importance for genetic counselling of delineating the Meckel syndrome from the multifactorial cases of neural tube defects, and also illustrates, at least in some cases, that the syndrome can be diagnosed in utero.

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