Objective To compare the diagnostic accuracy of the current reference standard-ultrasound with in utero magnetic resonance imaging, in a selected group of patients. Design Prospective study.Setting Five fetal maternal tertiary referral centres and an academic radiology unit.Sample One hundred cases of fetuses with central nervous system abnormalities where there has been diagnostic difficulties on ultrasound. In 48 cases the women were less than 24 weeks of gestation and in 52 cases later in pregnancy. Methods All women were imaged on a 1.5 T clinical system using a single shot fast spin echo technique. The results of antenatal ultrasound and in utero magnetic resonance were compared. Main outcome measures The definitive diagnosis was made either at autopsy or by postmortem magnetic resonance imaging, in cases that went to termination of pregnancy, or a combination of postnatal imaging and clinical follow up in the others. Results In 52 of cases, ultrasound and magnetic resonance gave identical results and in a further 12, magnetic resonance provided extra information that was judged not to have had direct effects on management. In 35 of cases, magnetic resonance either changed the diagnosis (29) or gave extra information that could have altered management (6). In 11 of the 30 cases where magnetic resonance changed the diagnosis, the brain was described as normal on magnetic resonance. Conclusions In utero magnetic resonance imaging is a powerful tool in investigating fetal brain abnormalities.Our results suggest that in selected cases of brain abnormalities, detected by ultrasound, antenatal magnetic resonance may provide additional, clinically useful information that may alter management.

Solid-state 13C CP MAS NMR studies of compounds [(Me3Sn),M(CN),], with M = Fe, Ru and Os, using variable temperature, show that the trigonal bipyramidal arrangements a t Sn are undergoing internal rotation about the N-Sn-N axes with lifetimes of the order of 0.5 s a t moderately lowered temperature.

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Total and differential leucocyte counts were measured in cord blood samples obtained by cordocentesis (n=316) or at elective caesarean section (n= l1) from normal fetuses of between 18 and 40 weeks' gestation. The total fetal leucocyte count increased exponentially from 2*8X109/l at 18 weeks to 11*8X109/l at term. The lymphocyte and monocyte counts increased linearly and the number of neutrophils increased exponentially from a mean value of 0.2 x 109/l at 18 weeks to 0-8 x 109/l at 31 weeks and then 8-5x109/l at term. Early myeloid cells, eosinophils, and basophils were observed in 24%, 55%, and 15% of the blood films respectively; they contributed less than 2% to the total leucocyte count and there were no significant changes with gestation. The physiological leucopenia observed in fetuses early in the third trimester may partly explain the predisposition of premature neonates to infection.

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Objective To assess the ability of ultrafast magnetic resonance imaging to visualise abnormalities in the central nervous system of third trimester fetuses in utero and to compare the results with the current`reference standard' of ultrasound and postnatal imaging or post-mortem data. Design A prospective, observational study comparing the diagnostic accuracy of two imaging methods: antenatal ultrasound and antenatal magnetic resonance with each other and postnatal or post mortem data.Population Twenty-one pregnant women of 19±36 weeks of gestation whose fetus were thought to have a central nervous system abnormality on the basis of antenatal ultrasound. The women had either not been offered or had refused a termination and were willing to have a magnetic resonance scan. Methods A 1.5T magnetic resonance scanner used a single shot fast spin echo sequence, in three image planes.The results were compared with the ultrasound results obtained by an experienced investigator independently. A series of 21 patients, with a range of pathologies of central nervous system, were imaged. Postnatal ultrasound and/or magnetic resonance imaging, or post-mortem data were used for additional con®rmation of the pathology in all cases.Results The magnetic resonance report was different to the ultrasound in 10/21 (47.6%), magnetic resonance provided information additional to the ultrasound in 5/21 (23.8%), ultrasound and magnetic resonance results agreed in 6/21 cases (28.6%). Conclusion Magnetic resonance in the third trimester provides a useful adjuvant to ultrasound imaging of the fetus when assessing abnormalities of the central nervous system after 19 weeks of gestation particularly if the abnormality involves the posterior fossa.

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