Sonographic measurements of the umbilical cord and vessels were performed in 368 uncomplicated pregnancies, and nomograms of their growth were constructed. All measurements were obtained in appropriate for gestational age fetuses in pregnancies with accurate dating. From the above measurements, an estimate of Wharton's jelly quantity (expressed as square millimeters) was calculated. The nomograms presented add another biometric measurement of normally growing fetuses and may serve to differentiate between them and those who are found to have umbilical cord abnormalities.

Sonographic measurements of the umbilical cord and vessels during normal pregnancies.

Umbilical cord morphology and pregnancy outcome.

Objective The purpose of this study was to investigate whether the prenatal diagnosis of a ‘lean’ umbilical cord in otherwise normal fetuses identifies fetuses at risk of being small for gestational age (SGA) at birth and of having distress in labor. The umbilical cord was defined as lean when its cross-sectional area on ultrasound examination was below the 10th centile for gestational age. Method Pregnant women undergoing routine sonographic examination were included in the study. Inclusion criteria were gestational age greater than 20 weeks, intact membranes, and singleton gestation. The sonographic cross-sectional area of the umbilical cord was measured in a plane adjacent to the insertion into the fetal abdomen. Umbilical artery Doppler waveforms were recorded during fetal apnea and fetal anthropometric parameters were measured. Results During the study period, 860 patients met the inclusion criteria, of whom 3.6% delivered a SGA infant. The proportion of SGA infants was higher among fetuses who had a lean umbilical cord on ultrasound examination than among those with a normal umbilical cord (11.5% vs. 2.6%, p < 0.05). Fetuses with a lean cord had a risk 4.4-fold higher of being SGA at birth than those with a normal umbilical cord. After 25 weeks of gestation, this risk was 12.4 times higher when the umbilical cord was lean than when it was of normal size. The proportion of fetuses with meconium-stained amniotic fluid at delivery was higher among fetuses with a lean cord than among those with a normal umbilical cord (14.6% vs. 3.1%, p < 0.001). The proportion of infants who had a 5-min Apgar score < 7 was higher among those who had a lean cord than among those with normal umbilical cord (5.2% vs. 1.3%, p < 0.05). Considering only patients admitted in labor with intact membranes and who delivered an appropriate-for-gestational-age infant, the proportion of fetuses who had oligohydramnios at the time of delivery was higher among those who had a lean cord than among those with a normal umbilical cord (17.6% versus 1.3%, p < 0.01).

Prenatal diagnosis of a lean umbilical cord : a simple marker for the fetus at risk of being small for gestational age at birth

Biomarkers are often applied to assess prenatal exposure to methylmercury in research and surveillance. In a prospective study in the Faroe Islands, the main exposure biomarkers were the mercury concentrations in cord blood and maternal hair obtained at parturition. We have now supplemented these exposure biomarkers with mercury analyses of umbilical cord tissue from 447 births. In particular, when expressed in relation to the dry weight of the tissue, the cord mercury concentration correlated very well with that in cord blood. Structural equation model analysis showed that these two biomarkers have average total imprecision of about 30%, which is much higher than the laboratory error. The imprecision of the dry-weight-based concentration was lower than that of the wet-weight-based parameter, and it was intermediate between those of the cord blood and the hair biomarkers. In agreement with this finding, regression analyses showed that the dry-weight cord mercury concentration was almost as good a predictor of methylmercury-associated neuropsychologic deficits at 7 years of age as was the cord-blood mercury concentration. Cord mercury analysis can therefore be used as a valid measure of prenatal methylmercury exposure, but appropriate adjustment for the imprecision should be considered.

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R.S. Brown

Papers

The water content of the human umbilical cord.