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Biomedical subjects

M Mongelli

Publications and source records attributed to M Mongelli.

At least 19 recordsLinked to original sources
PubMed2005

Third-trimester ultrasound dating algorithms derived from pregnancies conceived with artificial reproductive techniques.

OBJECTIVE: To derive an accurate formula for ultrasound estimation of gestational age in late pregnancy. METHODS: A database of 123 singleton pregnancies conceived by artificial reproductive techniques with third-trimester ultrasound measurements was studied. Biometry variables included the fetal head circumference (HC) and femur length (FL). The dataset was equally divided into a derivation sample and a target sample. To derive the equations of best fit, regression analysis was used, with true menstrual age as the dependent variable and fetal biometry measurements as independent variables. The formulae were tested on the target set and the menstrual age estimates were compared with the actual menstrual age. Clinical performance was estimated in terms of systematic and random errors, absolute errors and their 95% CI values. RESULTS: The menstrual ages at time of scanning ranged from 26 to 41 weeks, with a mean of 33 weeks. The best performing derived formula was a combination of HC and FL. This had a random error of 7.5 days and prediction errors within a 95% confidence limit of -13 to +17 days. With FL only, the random error was 8.2 days, whereas using the HC only yielded a random error of 9.4 days. CONCLUSIONS: Ultrasound estimation of gestational age in late pregnancy is better than indicated by older publications. It is more accurately estimated by combining the HC with the FL than by using the FL measurements alone.

Algorithms↗
PubMed2005

Ultrasound diagnosis of fetal macrosomia: a comparison of weight prediction models using computer simulation.

OBJECTIVE: To assess the frequency of the diagnosis of macrosomia in relation to differing weight estimation formulae in unselected pregnancies. METHODS: Computer modeling techniques were employed. Computer modeling software generated correlated fetal biometry measurements according to published British standards, from 37 to 41 weeks' gestation. For each set of measurements, estimated fetal weights were obtained by a panel of 18 ultrasound weight formulae. The diagnosis of macrosomia was made if the fetal weight estimate was greater than 4500 g. Cohorts of 5000 pregnancies for each week of gestation were studied. RESULTS: The frequency of diagnosis of macrosomia increased progressively with advancing gestational age, with large increases between 40 and 41 weeks. The type of weight estimation formula had a profound influence on the frequency of diagnosis of macrosomia. Five of the formulae tested almost never returned a weight estimate greater than 4500 g. Three formulae yielded false positive rates in excess of 15%. The Hadlock group of formulae yielded frequencies of 0.3% to 14.6%. CONCLUSIONS: Most formulae tend to over-diagnose macrosomia at term. Intervention rates for suspected fetal macrosomia may be influenced by gestational age at the time of scan and the type of fetal weight estimation formula in use.

Birth Weight↗
PubMed2005

Z-velocity in screening for intrauterine growth restriction.

OBJECTIVES: Ultrasound scans provide the basis for detection of intrauterine growth restriction (IUGR) but often fail to distinguish IUGR from small-for-gestational age (SGA) fetuses. This study introduces the concept of Z-velocity, calculated as changes in Z-scores over time, as an additional criterion in the diagnosis of IUGR. METHODS: A computer program simulated 50 000 fetal abdominal circumference (FAC) scans based on published growth formulae. False-positive rates were calculated to determine optimal scan time and scan intervals. Using an independent simulation of 32 500 FAC scans, the two methods were compared using receiver-operating characteristics (ROC) curve analysis. RESULTS: ROC showed areas under the curve of > 0.74 over the complete range of scan intervals. The positive predictive value of growth arrest as the only diagnostic criterion was, however, too low to recommend it as an exclusive or the first diagnostic criterion. CONCLUSIONS: Z-velocity can be used to decide whether further investigations for growth abnormality are required in fetuses that fall below the 10(th) percentile. The gain of combined diagnostic approaches should be calculated from large databases that include the neonatal ponderal index as the gold standard.

Diagnosis, Differential↗
PubMed2003

Attitudes of Singapore women toward cesarean and vaginal deliveries.

OBJECTIVES: To assess the attitude, knowledge, and expectations of Asian pregnant women toward cesarean and vaginal deliveries. METHODS: Written questionnaires were given to pregnant women attending the National University Hospital antenatal clinics, and 160 responses were tabulated and analyzed using SPSS software. RESULTS: The participation rate was 65% and 50% of the respondents were Chinese, 20% Indian, 21% Malay, 2% White, and 9.2% Other. The median age was 31 years, and approximately 43% were primiparas. Only 3.7% of them would prefer an elective cesarean delivery, and although 50% had friends or relatives who requested one, only 3% felt that this influenced their preference. The most common reasons for choosing a cesarean delivery were avoiding labor pains and lowering the risk of fetal distress. When asked which modality they would recommend to their friends, only 2% expressed that they would recommend cesarean delivery; however, 71% stated that women should have the right to request a cesarean delivery. Awareness of complications arising from vaginal and cesarean deliveries was generally low and related to the frequency of these complications. There was no significant correlation between demographic characteristics and maternal preference for mode of delivery. CONCLUSIONS: Asian women largely prefer a vaginal delivery, and their attitude toward cesarean delivery on demand is comparable with that of Western women. Cultural or ethnic differences are unlikely to affect maternal preference for cesarean delivery in Singapore women.

Adolescent↗
PubMed2003

Accuracy of ultrasound dating formulae in the late second-trimester in pregnancies conceived with in-vitro fertilization.

PURPOSE: To investigate the accuracy of ultrasound dating formulae in the late second trimester of pregnancy. MATERIAL AND METHODS: A dataset of 136 singleton pregnancies conceived by artificial reproductive techniques was studied to assess the accuracy of ultrasound dating formulae in the late second trimester, and compared with early second trimester. A total of 21 published ultrasound-dating formulae were tested. RESULTS: For most formulae, late second trimester scans yielded results that were marginally less accurate than the early second trimester. The best performance was obtained with dating formulae based on femur length, either alone or combined with the biparietal diameter. These formulae had mean absolute errors of 3-3.5 days. Combining two or more parameters did not result in any substantial gain in accuracy. CONCLUSIONS: Pregnancy dating by ultrasound in the late second trimester is sufficiently accurate for routine clinical use. Formulae based on femur length appear to be at least as accurate as head measurements.

Adult↗
PubMed2003

Factors influencing fetal growth.

Birth weight remains one of the most important measures we have of the health status of a population, and is a strong predictor of both neonatal mortality and morbidity. It reflects maternal nutritional status and fetal growth rates in the antenatal period. Although a large number of physiological and pathological variables can affect the growth rate, for most cases of growth-restricted fetuses a cause cannot be determined. Awareness of the physiological aspects of fetal growth is important in assessing whether the fetus is growing normally. This article is a review of recent findings and key historical material on factors influencing birth weight.

Embryonic and Fetal Development↗
PubMed2001

A fetal growth standard derived from multiple modalities.

OBJECTIVE: To create a fetal weight growth standard from published data on ultrasound-dated pregnancies. METHODS: A fetal growth standard was calculated from published birth weight data, sonographic weight standards, and one MRI study. The birth weights from the East Midlands Obstetric Database were modified by an incremental function to compensate for the lower weights of preterm infants. Published sonographic and MRI standards, and the modified birth weight curve were transformed to yield fractional growth curves that express fetal size as a proportion of the expected term weight. These three curves were then averaged, and the standard deviation was taken as 12% of the median. Curves for Europeans and Chinese were then generated. RESULTS: The average curve for fetal weight is a virtually linear function of gestational age, with a weekly weight gain of 5.2% of the expected term birth weight. CONCLUSIONS: Ultrasound-derived fetal growth curves are subject to bias inherent in weight estimation formulae. A standard derived from multiple modalities is likely to be a more robust estimate of normal fetal growth.

Birth Weight↗
PubMed2001

Induction policy and missed post-term pregnancies: a mathematical model.

The aim of this study was to compare the clinical performance of ultrasound dates and ultrasound dates combined with menstrual dates for the detection of post-maturity. A computer model was designed which uses the statistical distributions of the duration of normal pregnancy, day of ovulation in relation to the menstrual cycle and ultrasound error for estimating gestational age. The clinical performance of the different dating methods was then analysed from these variables, on simulations of 30,000 cases. The efficacy of different dating methods for detecting post-maturity was determined by generating receiver-operator characteristics (ROC) curves. The proportion of post-term pregnancies (294 days and over) predicted by the model (3.5%) agrees with published values. There is a steep rise in missed cases if induction is delayed beyond 10 days from the expected date of delivery, reaching 20% on day 294. Elective delivery on day 290 will detect 98.9% of cases destined to deliver post-term, with an induction rate of 10%; the respective figures for induction on day 294 are 79% and 3.8%. The ROC curves for the detection of post-maturity suggest that use of the mid-trimester biparietal diameter (BPD) is better than a 7-day or 10-day rule. Timing of elective delivery is the most important variable affecting the detection rate for post-maturity There is no advantage in using menstrual dates when ultrasound biometry is available.

Bias↗
PubMed2000

Sociobiological variables and pregnancy outcome.

Recent advances are beginning to shed light on the mechanisms whereby adverse psychosocial factors can influence pregnancy outcome. High levels of maternal stress have been linked to endocrine disturbances, which in turn increases the risk of preterm labor considerably. These observations have been supported by experimental animal models. Birth weight is subject to considerable ethnic variation, and on its own is a nonspecific indicator of pregnancy outcome. The benefits of social and psychological intervention have been best documented in the intrapartum situation, whereas antenatal intervention is most likely to be of benefit when focused on improving socioeconomic conditions and access to healthcare providers.

Birth Weight↗
PubMed2000

Fetal growth.

Recent epidemiological and experimental studies show that abnormal fetal growth can lead to serious complications, including stillbirth, perinatal morbidity and disorders extending well beyond the neonatal period. It is now clear that the intrauterine milieu is as important as genetic endowment in shaping the future health of the conceptus. Maternal characteristics such as weight, height, parity and ethnic group need to be adjusted for, and pathological factors such as smoking excluded, to establish appropriate standards and improve the distinction between what is normal and abnormal. Currently, the aetiology of growth restriction is not well understood and preventative measures are ineffective. Elective delivery remains the principal management option, which emphasizes the need for better screening techniques for the timely detection of intrauterine growth failure.

Embryonic and Fetal Development↗
PubMed2000

Effect of labour and delivery on plasma hepatic enzymes in the newborn.

OBJECTIVE: To study the relationship between cord blood hepatic enzymes and obstetric and neonatal outcome in a Chinese population. MATERIALS AND METHODS: The study group consisted of 288 low-risk Chinese women with singleton term pregnancies. The following enzymes were assayed in cord blood: lactate dehydrogenase (LDH), glutamyl transferase (GGT), aspartate aminotransferase (AST) and alanine transferase (ALT). These were correlated to maternal and neonatal characteristics. RESULTS: A strong correlation was noted between cord blood AST and LDH (R = 0.582, p < 0.01), which was absent amongst those infants delivered by elective cesarean section. LDH, AST and ALT were negatively correlated with cord arterial pH and base excess (BE). GGT was inversely related only to gestational age (R = -0.18, p < 0.01). Both LDH and AST were weakly correlated with the duration of the first and second stages of labour. LDH was most closely linked to arterial pH, whereas AST was related to both arterial BE and duration of the second stage. CONCLUSIONS: The reference values are comparable to those published for Caucasian populations. There are moderate elevations in LDH and AST associated with the onset of labour and changes in acid-base status.

Acid-Base Equilibrium↗
PubMed1999

Symphysis-fundus height and pregnancy characteristics in ultrasound-dated pregnancies.

OBJECTIVE: To investigate the relation between maternal and pregnancy characteristics and symphysis-fundus height values at term in an obstetric population dated by sonography. METHODS: Three hundred twenty-five women were recruited from the antenatal clinics of the Queen's Medical Centre, Nottingham, United Kingdom for measurement of fundal height and for ultrasound scans. Symphysis-fundus height measurements were analyzed by multivariate regression analysis in relation to gestational age, maternal height and weight, ethnic group, and smoking. RESULTS: Gestational age and maternal characteristics explained nearly half of the variability in symphysis-fundus height. Gestational age was the most important determinant, followed by maternal weight, parity, and sex of the infant. The other variables were not significantly correlated. CONCLUSION: Maternal characteristics had statistically significant effects on the expected symphysis-fundus height, which suggests that individually adjusted fundal height charts may improve the precision of clinical screening for fetal growth restriction.

Adolescent↗