Analysis of fetal and neonatal urine using proton nuclear magnetic resonance spectroscopy

AIM

To use high field proton nuclear magnetic resonance spectroscopy (1H NMR) to characterise the low molecular weight metabolite composition of neonatal and fetal urine in relation to gestational age and perinatal outcome.

METHODS

The first urine passed by two neonatal groups, six full term and five preterm infants with normal renal function, was analysed by 1H NMR and compared with fetal urine from 14 cases with obstructive uropathy.

RESULTS

The mean ratios of taurine, myo-inositol, and trimethylamine-N-oxide (TMAO) to creatinine were 4.3, 10.1, and 14.1 times higher, respectively, in the preterm group when compared with those of the full term group. Fetal obstructive uropathy was characterised by glycosuria, amino and organic aciduria, regardless of gestational age (13-30 weeks).

CONCLUSIONS

Samples of the first urine passed--that is, urine produced in fetal life--by normal preterm infants are useful controls for cases of obstructive uropathy detected in the third trimester. 1H NMR will become a clinically useful tool for monitoring renal development and abnormalities in utero.

First trimester fetal nuchal translucency: problems with screening the general population. 1

OBJECTIVE

To evaluate the feasibility of measuring first trimester nuchal translucency in an unselected population, to assess the relationship with gestation and maternal age and to measure reproducibility.

DESIGN

A prospective observational study.

SETTING

University College Hospital, London.

SUBJECTS

One thousand and four women attending for a routine first trimester dating scan between eight and thirteen weeks of gestation. Measurements of nuchal translucency were attempted in 1368 (80.3%) and successful in 1127 (82% of attempts).

RESULTS

Nuchal translucency is most easily measured at 11 weeks of gestation. If a cut-off of > or = 3 mm is used, 6% of unselected fetuses between eight and thirteen weeks of gestation are classified as abnormal. Nuchal translucency increases with gestational but not maternal age. Reproducibility is poor: by repeating measurements with a different operator, the same operator using a different still image, or the same operator using the same still image, 18.8%, 17.5% or 12.4% of nuchal translucency measurements, respectively, change their classification as normal or abnormal.

CONCLUSIONS

If nuchal translucency > or = 3mm were used as an indication for karyotyping, 6% of the normal pregnant population would be screen positive. However, the percentage will vary greatly depending on the gestational age profile of the screened population. The poor reproducibility of nuchal translucency measurement could diminish its usefulness as a screening test for Down's syndrome.

First trimester fetal nuchal translucency: problems with screening the general population. 2

OBJECTIVE

To investigate first trimester nuchal translucency > or = 3 mm as a screening test for aneuploidy in the normal pregnant population.

DESIGN

A pilot observational study.

SETTING

University College Hospital, London.

SUBJECTS

One thousand one hundred and twenty-seven women had measurements of nuchal translucency at the time of their dating scan (8-13 weeks of gestation).

RESULTS

Seventy fetuses (6%) had a nuchal translucency > or = 3 mm. Five karyotypically abnormal fetuses were identified by standard routine techniques (three trisomy 21, two trisomy 18), all in high risk mothers (> or = 39 years). Only two had nuchal translucency > or = 3 mm (one trisomy 21, one trisomy 18).

CONCLUSIONS

Although nuchal translucency measurement is feasible and promising, there is at present insufficient data to warrant its introduction for screening of the general population, or to replace traditional second trimester screening.

The introduction of external cephalic version at term into routine clinical practice

External cephalic version (ECV) at > or = 37 weeks' gestation in suitable women with breech presentation was introduced in 1991 as a new management option at a University Teaching Hospital. After 16 months, the policy was audited by analysing a prospectively collected database of women offered ECV at term and by a retrospective review of all breech deliveries during the same period. A total of 52 women had ECV attempted with an immediate success rate of 46%. Four other cases had undergone spontaneous version by the time they attended for ECV. Of the remaining 72 breech deliveries, 49 were known to be breech and were not offered ECV; 39 of these had no contraindication (28% failure to offer ECV). Of the breech presentations, 22 remained undiagnosed until labour (18% of total study group). These results suggest that ECV at term can be introduced safely and without difficulty, with a strict protocol. Whilst the overall impact of ECV at term in clinical practice may be limited, if some vaginal breech deliveries and caesarean sections can be avoided it is a useful addition to the antenatal management of individual women with breech presentation.

Uteroplacental resistance index: analysis of intra- and interobserver variability

The aim of this study was to assess the intra- and interobserver variability of second-trimester uteroplacental continuous-wave flow velocity waveforms. The left and right uterine and arcuate resistance indices were measured in women having their routine booking scan at 16-24 weeks' gestation. Four experiments assessed the intra-observer between-frame variability, the intraobserver beat-to-beat variability, the intraobserver temporal variability, and the interobserver variability, using the limits-of-agreement method. The intraobserver between-frame variability was greater than the beat-to-beat variability at three of the four sites. The temporal variability was not significantly different between sites. There were wide interobserver limits of agreement with respect to the reference ranges, although they were greater at arcuate sites than uterine sites. These observations suggest that the reproducibility of the resistance index in continuous wave Doppler uteroplacental flow velocity waveforms is poor, particularly from arcuate sites. The uterine site is preferable and descriptive analysis may be better.

The relationship of uterine and umbilical Doppler resistance to fetal and placental protein synthesis in the second trimester

The relation of uteroplacental and umbilical Doppler resistance index (RI) to peripheral levels of alphafetoprotein (AFP), human chorionic gonadotrophin (hCG), human placental lactogen (HPL), Schwangerswaft protein (SP1), pregnancy-associated placental protein A (PAPP-A) and insulin-like growth factor binding protein 1 (IGP-BP1) at 16-24 weeks was established in a cross-sectional study of 183 unselected singleton pregnancies. There was an association between high values of uteroplacental RI and high hCG levels, and high umbilical RI values with high hCG and HPL levels. Thus, in the mid-trimester, the levels of some placental proteins seem to be related to placental resistance.

Improved prediction of preeclampsia by two-stage screening of uterine arteries using the early diastolic notch and color Doppler imaging

OBJECTIVE

To assess the value of the early diastolic notch and color Doppler imaging of the uterine arteries at 24 weeks' gestation in a two-stage Doppler screening test for preeclampsia.

METHODS

Two thousand fifty-eight unselected women had an initial screening study with continuous-wave Doppler at 18-22 weeks' gestation. Color Doppler imaging was used at 24 weeks' gestation to examine both uterine arteries in 273 women with initial abnormal results (high resistance index or diastolic notch).

RESULTS

Three hundred twenty-nine women (16%) had abnormal flow velocity waveforms at the first stage and 104 (5.1%) at the second stage of Doppler screening. The presence of an early diastolic notch in the flow velocity waveform was significantly better than a high resistance index at predicting preeclampsia at both 20 and 24 weeks; the relative risk of developing significant preeclampsia for a woman with a persistent notch at 24 weeks was increased 68-fold. All women delivered before 34 weeks because of severe preeclampsia had abnormal waveforms at both stages of screening.

CONCLUSION

An early diastolic notch in the flow velocity waveform is a better predictor of preeclampsia than are conventional impedance indices. Preeclampsia can be predicted effectively by two-stage Doppler screening.

Early prediction of uteroplacental complications of pregnancy using Doppler ultrasound, placental function tests and combination testing

In a prospective, blind study of 183 unselected women attending for routine booking scan with a singleton pregnancy at 16-24 weeks' gestation, uteroplacental resistance index, and peripheral levels of alpha-fetoprotein, human chorionic gonadotropin, human placental lactogen, Schwangerswaft protein, pregnancy-associated placental protein A and insulin-like growth factor (IGF) binding protein 1 were measured. High levels of alpha-fetoprotein and IGF 1 binding protein 1 (> 90th centile) were associated with small-for-gestational age babies (< 10th centile) (sensitivity 24% and 22%; specificity 90% and 91%). High levels of alpha-fetoprotein, human chorionic gonadotropin and pregnancy-associated placental protein A (> 90th centile) were associated with one or more of three severe complications of pregnancy: very small-for-gestational age (< 3rd centile), severe proteinuric hypertension or intrauterine death (sensitivity 20%, 20% and 57%; specificity 90%, 95% and 91%, respectively). A uteroplacental resistance index > 90th centile was also associated with small-for-gestational age and severe complications (sensitivity 24% and 50%, specificity 90% and 90%). A combination of resistance index and a placental function test improved the prediction for a group of patients that included any complications (sensitivity 31% and specificity 89%). Doppler ultrasound was a more efficient predictor than individual placental function tests but screening predictions can be improved by combining Doppler parameters and placental protein estimations. Combinations of placental function tests might provide equivalent, or complementary, information. This preliminary work demonstrates the potential value of combining biophysical and biochemical tests to predict complications of pregnancy.

The law, medical students, and assault

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Drug dependence with oestrogen replacement therapy

Dependence on some drugs can be hard to recognize. Hormone replacement therapy (HRT) has been widely prescribed only in the past two decades, and the indications for treatment and the risk/benefit ratio are still disputed. Oestrogens are psychoactive: they lift mood, can be given by injection, and their use has powerful psychological effects. Reports of women with supraphysiological oestradiol concentrations may represent tolerance and withdrawal. Dependence on substances occurring naturally in the body has been reported before. We propose that HRT dependence occurs.

Doppler velocimetry studies of the uterine artery in the early prediction of pre-eclampsia and intra-uterine growth retardation

Pre-eclampsia/proteinuric pregnancy-induced hypertension (PPIH) and intra-uterine growth retardation (IUGR) are associated with incomplete trophoblastic invasion of the uterus in the first half of pregnancy. The uteroplacental circulation can be observed using Doppler ultrasound. We have performed two mid pregnancy screening studies of our antenatal population in the last three years, to assess the use of Doppler velocimetry studies at that time in predicting the subsequent development of PPIH and IUGR. In the first study continuous wave Doppler ultrasound was used to study the uterine circulation. The Resistance Index (RI) was measured once in both uterine arteries in 925 patients between 16 and 24 weeks gestation. There was a significant association between an abnormal RI (greater than 95th centile) and the subsequent development of PPIH, IUGR and severe complications of pregnancy. However, even though the specificity (95%) was high the sensitivity was low (25%). There was no significant association with nonproteinuric hypertension. In an attempt to improve the sensitivity for the second study, colour flow imaging and the use of a diastolic notch as well as an elevated RI were introduced. 2437 patients had continuous-wave Doppler studies of the uterine circulation performed at 20 weeks gestation. 16% had abnormal waveforms, persisting in 5.4% at 24 weeks and 4.6% at 26 weeks when measured with colour/pulsed Doppler. The high sensitivity (76%) of this innovation at 20 weeks is retained at 24 and 26 weeks, while the specificity (from 86% to 97%) and positive predictive value (13% to 44%) improve progressively with gestation.(ABSTRACT TRUNCATED AT 250 WORDS)

Doppler investigation of uteroplacental blood flow resistance in the second trimester: a screening study for pre-eclampsia and intrauterine growth retardation

OBJECTIVE

To assess the screening properties of a mid-trimester uteroplacental Doppler scan in a normal unselected population.

DESIGN

A cross-sectional study measuring an averaged resistance index (AVRI) from four sites (left and right uterine and arcuate arteries) with continuous wave Doppler ultrasound.

SETTING

Routine booking ultrasound, King's College Hospital, London.

SUBJECTS

977 women at 16-24 weeks gestation.

MAIN OUTCOME MEASURES

Intrauterine death, birthweight, pregnancy-induced hypertension (PIH), antepartum haemorrhage.

RESULTS

There was a 96.5% follow-up. Pregnancies with high AVRI values had a higher prevalence of proteinuric hypertension, placental abruption, small-for-gestational-age babies, and fetal loss. When AVRI was greater than 95th centile, the overall risk of pregnancy complications was 67%, and the risk of a severe complication was 25%. However, the sensitivity of the test for these complications was only 13% and 21% respectively. The risk for an individual woman with a high AVRI of developing a complication was increased by up to 9.8 times.

CONCLUSION

Although Doppler screening does detect a unifying defect leading to perinatal death, pre-eclampsia, growth retardation and placental abruption, the predictive values do not yet justify its introduction as a routine test.

Maternal death associated with ovum donation twin pregnancy

A case of maternal death due to sub-arachnoid haemorrhage in an ovum donation twin pregnancy complicated by hypertension is described. Attention is drawn to a forecasted increase in maternal morbidity and mortality in in-vitro fertilization (IVF) pregnancies, which occur in older women and are often multiple.

Uteroplacental Doppler flow velocity waveforms in the second trimester. A complex circulation

Continuous wave Doppler ultrasound was used to examine the uteroplacental circulation of an unselected group of 977 [corrected] women between 16 and 24 weeks gestation. Reference ranges for resistance index (RI) were determined and throughout this gestation range there was a significant fall in RI with increasing gestation. The RI was lower from placental than non-placental sites and from distal 'arcuate' than proximal 'uterine' sites. There is a need to define fixed standardized sites for sampling and for normal ranges to account for variables such as placental site.

Who defaults after treatment for gonorrhoea? Randomised controlled study of effect of an educational leaflet

A study of patients with gonorrhoea showed that those who defaulted most from follow up were male, heterosexual, and had multiple sexual partners. A prospective, blind, randomised controlled trial showed that a leaflet giving information about gonorrhoea had a positive effect on follow up attendance by women, but no appreciable effect on rates of defaulting overall. This has implications for the initial treatment schedules.

Investigation of the uteroplacental circulation by Doppler ultrasound

Doppler assessment of the uteroplacental circulation can be performed easily. In early pregnancy, it may identify pregnancies at risk of developing pregnancy-induced hypertension and IUGR. In late pregnancy, a high impedance in the uteroplacental vascular bed indicates that the fetus is at risk of developing hypoxia, but the fetal and umbilical FVW are the best indicators of immediate fetal well-being. Doppler ultrasound also offers the potential for noninvasive experimental hemodynamic studies of the uteroplacental circulation.