PubMed Health⌕ Search

Biomedical subjects

J P Neilson

Publications and source records attributed to J P Neilson.

At least 55 records · Page 3Linked to original sources
PubMed1995

Spiral artery blood flow in the central and peripheral areas of the placental bed in the second trimester.

OBJECTIVE: To assess impedance to blood flow through spiral arteries in the central and peripheral areas of the placental bed, to determine if in vivo findings are in concordance with histologic observations of cytotrophoblast invasion. METHODS: This study was cross-sectional, using transabdominal color flow and pulsed Doppler imaging in 64 women with normal, singleton pregnancies at 17-20 weeks' gestation. Spiral arteries were visualized by color Doppler in the central and peripheral parts of the placental bed, and blood flow was analyzed using pulsed Doppler to calculate the resistance index (RI) and the pulsatility index (PI). RESULTS: Visualization of flow in the spiral arteries was achieved in 100% of cases in the central area and in 95% in the periphery. Both the RI and PI were significantly lower in the center compared with the periphery (P < .001). There was no significant difference in the peak systolic velocities between the two areas. Regression analysis showed no significant difference in RI or PI at the different weeks of gestation in the central and peripheral areas of the placental bed. CONCLUSION: Impedance to blood flow through spiral arteries in the second trimester is lower in the central area of the placental bed, and is in agreement with previous histologic data. Physiologic change of the spiral arteries is functionally complete around 17 weeks' gestation.

Adult↗
PubMed1995

Effective care in pregnancy and childbirth: a synopsis.

Evidence about the effects of care practices is not a sufficient guide to the most appropriate care. Those who provide care, who receive care, who advocate care, or who pay for care must choose on the basis of many factors: personal experience, personal preference, personal values, availability of resources and facilities, and a myriad of other considerations, among which knowledge of the effects of care is certainly important. This knowledge is essential for choices to be properly informed. The most reliable evidence about the effects of care is provided by randomized controlled trials. Unfortunately, this evidence is not readily accessible. It is scattered through a large number of journals throughout the world, and is hidden among a mass of weak, inadequate, and sometimes frankly misleading studies. Those who wish to use all the valid evidence must rely on properly prepared, up-to-date, systematic reviews. The Cochrane Collaboration has taken on the task of preparing, maintaining, and disseminating reviews of randomized trials of health care, published electronically as the Cochrane Database of Systematic Reviews. The reviews are provided by a number of Collaborative Review Groups, and the Cochrane Pregnancy and Childbirth Database is the first specialty database to appear. It is regularly updated to incorporate data that have become available since the previous issue.

Delivery, Obstetric↗
PubMed1994

Prenatal diagnosis of fragile X syndrome: management of the male fetus with a premutation.

Direct detection of the fragile X mutation by DNA analysis has greatly simplified prenatal diagnosis of this disease. However, women carrying a fragile X premutation may pass their expanded trinucleotide repeat to sons without expansion to a full mutation. Such sons are predicted to be intellectually normal. In this situation, the accuracy with which the fetal status can be inferred from analysis of chorionic villus sample (CVS) DNA is unclear. We describe such a case, in which it was felt necessary to proceed to fetal blood sampling despite technically unambiguous DNA results from the CVS. The lack of prospective data means that this dilemma may be expected to recur over the next few years when performing prenatal diagnosis on fragile X premutation carriers.

Adult↗
PubMed1994

Screening for the compromised fetus: a randomized trial of umbilical artery velocimetry in unselected pregnancies.

OBJECTIVE: Meta-analysis of randomized trials of Doppler ultrasonography in high-risk pregnancies has showed reduced mortality rates among normally formed fetuses. This trial addressed the impact on outcome of umbilical artery velocimetry in a nonselected population (i.e., as a screening test in low-risk and high-risk pregnancies). STUDY DESIGN: A randomized, controlled trial with Doppler ultrasonographic investigation was performed at two gestational age windows: 26 to 30 weeks and 34 to 36 weeks. The 2986 women were randomly allocated to revealed or concealed groups in which the Doppler results were either made available or not made available to clinicians; 1056 women were studied at only the first window, 544 at only the second, and 1386 at both. RESULTS: There were no significant differences between groups in antenatal admissions to hospital, preterm deliveries, rates of cesarean section, admission to the neonatal unit, and need for assisted ventilation. There was, however, a trend toward fewer stillbirths in the "revealed" group (three vs eight, odds ratio 0.34, confidence interval 0.10 to 1.07). CONCLUSIONS: The incidence of stillbirths was reduced by more than half in the Doppler-revealed group, but the confidence intervals were wide and these findings could be compatible with chance.

Adult↗
PubMed1992

Prenatal diagnosis in multiple pregnancies.

Multiple pregnancy, with its high rate of fetal loss and increasing incidence, merits greater clinical attention and research. Prenatal diagnosis in multiple pregnancy poses particular difficulties in terms of safety and technique of invasive procedures, interpretation of laboratory results, and the human dilemmas produced by the demonstration of discordant abnormality. Recent applications of ultrasound, including Doppler ultrasound, are also discussed in the context of the monochorionic placenta, prediction of preterm labor, and detection of intrauterine growth retardation.

Amniocentesis↗
PubMed1990

The effects of hospitalization for rest on fetal growth, neonatal morbidity and length of gestation in twin pregnancy.

OBJECTIVE: To test whether a policy of hospitalization for bed rest, from 28-30 weeks gestation until delivery, lengthens the duration of gestation, improves fetal growth and decreases neonatal morbidity in twin pregnancy. DESIGN: A randomized controlled trial. SETTING: Harare Maternity Hospital, Zimbabwe. SUBJECTS: 118 women with an uncomplicated twin pregnancy between 28 and 30 weeks gestation. INTERVENTION: Hospitalization for bed rest. Encouraged to rest in bed as much as possible, although voluntary ambulation was allowed. MAIN OUTCOME MEASURES: Gestational age at delivery and number of infants delivered preterm (less than 37 weeks); birthweight and number of small-for-gestational age (SGA) infants; neonatal morbidity was assessed by number of infants requiring admission to the neonatal unit and the length of stay. RESULTS: There was no effect on duration of gestation or the occurrence of preterm delivery. Mean birthweight was greater in the hospitalized group (t = -2.28, df 234, P = 0.02) and there were fewer SGA infants (OR 0.57, 95% CI 0.33-0.96). No differences were found in neonatal morbidity. CONCLUSIONS: Hospitalization for bed rest does not prolong pregnancy but can improve fetal growth, although this was not reflected in improved neonatal morbidity. Whether twin fetal growth can be enhanced similarly in other populations should be investigated.

Bed Rest↗
PubMed1989

Coitus, twin pregnancy, and preterm labor.

The effect of coitus on precipitation of preterm labor was studied prospectively in 126 women with twin pregnancies. All of the women attended a special antenatal clinic in a tertiary referral center and were questioned about the frequency of coitus. Of the participants, 40% reported coitus early in the third trimester; the rate decreased to 24% by 36 weeks' gestation. There were no significant differences in the frequency of positive responses between those who went into labor before term when contrasted with those who were delivered of infants at term. The data indicate that coitus is not an important precipitant of preterm labor in this high-risk group and that coitus need not be discouraged in women with twin pregnancies.

Adult↗
PubMed1989

Twin-to-twin transfusion syndrome: what are appropriate diagnostic criteria?

One hundred seventy-eight consecutive twin pregnancies were studied to reevaluate the standard diagnostic criteria for chronic twin-to-twin transfusion syndrome of an intertwin hemoglobin difference greater than 5 gm/dl and a birth weight difference greater than 20%. Hemoglobin differences greater than 5 gm/dl were found in six pregnancies with monochorionic placentas but also in seven with dichorionic placentas. Birth weight differences greater than 20% occurred no more commonly in monochorionic than in dichorionic pregnancies. Of the four pregnancies with a coexisting hemoglobin difference greater than 5 gm/dl and birth weight difference greater than 20%, only one had a monochorionic placenta and therefore likelihood of vascular anastomoses. Diagnosis of twin-to-twin transfusion syndrome cannot be definitively established by current standard diagnostic criteria.

Birth Weight↗
PubMed1989

Pregnancy screening by Doppler uteroplacental and umbilical artery waveforms.

Doppler waveforms from the uteroplacental and umbilical arteries were studied in 543 unselected women attending an antenatal clinic. Overall, 357 women were studied at 26-30 weeks and 395 at 34-36 weeks; 209 were studied at both gestation periods. Results were not made available to clinicians. There was no difference in outcome of pregnancies between those with normal and abnormal uteroplacental waveforms, but birthweights were significantly lower in those with an abnormal umbilical artery waveform at either gestation. There were no other statistically significant differences between groups. Although the power of the study to detect differences in outcome in this sample size is limited, our findings do not support the introduction of this new technique into clinical practice before sufficiently large randomized controlled trials have shown some benefit.

Adult↗
PubMed1989

Preterm labour in twin pregnancies: can it be prevented by hospital admission?

Women attending a twin pregnancy antenatal clinic underwent cervical palpation to calculate a cervical score by subtracting dilatation from length. Those with a score of -2 or less at or before 34 weeks are at especially high risk of preterm labour. A total of 139 such women were randomly allocated either to receive bed-rest in hospital or to continue conventional outpatient management. No beneficial effect of bed-rest could be identified in prolonging twin pregnancy or improving fetal outcome.

Bed Rest↗
PubMed1989

Monozygotic twin pregnancy: diagnostic and Doppler ultrasound studies.

Of 178 consecutive twin pregnancies, 63 were both monozygotic and also studied prenatally by real-time B-scan (and usually Doppler) ultrasound. The 48 pregnancies with monochorionic placentas (in which vascular anastomoses are almost universal) were compared with the 15 monozygotic pregnancies having dichorionic placentas. The type of placenta found at delivery was predicted with substantial accuracy by ultrasound examination in mid-pregnancy. We were unable to identify any inter-group difference in fetal growth rate, discordance of fetal growth between twins or pattern of umbilical artery flow velocity waveform. In the absence of the rare florid twin transfusion syndrome, the vascular anastomoses that have been shown to be common in monochorionic placentas do not exert a strong influence on fetal growth or fetoplacental blood flow.

Abdomen↗