Kevin J. Dalton

Morphometric differences between the placental vasculature of non‐smokers, smokers and ex‐smokers

Summary. The aim of this study was to determine whether cigarette smoking during pregnancy has an adverse effect upon the placentas capacity for gaseous exchange. Using recently developed stereological techniques, in conjunction with perfusion fixation, computer‐assisted measurements were made on the placentas of 15 non‐smokers, 15 moderate smokers, 15 heavy smokers and 13 ex‐smokers, 7 of whom stopped smoking during the course of the pregnancy. Compared with the placentas of non‐smokers and of those who stopped before pregnancy, it was found that the placentas of smokers and of those who stopped after conception exhibited a reduced capillary volume fraction, and an increased thickness of the villous membrane. Although they must impair gaseous exchange across the placenta, these changes were less severe than suggested by previously published reports. Nonetheless it is clear that in order to prevent these changes women should stop smoking before conception rather than during the course of a pregnancy.

Excessive Secretion of Insulin Precursors Characterizes and Predicts Gestational Diabetes

Using assays that specifically measure insulin, intact proinsulin, and 32,33 split proinsulin, we examined the β-cell secretory response to an oral glucose tolerance test (OGTT) in 64 women with gestational diabetes mellitus (GDM) and 154 pregnant normoglycemic control subjects of comparable age and body mass index. Women with GDM were characterized by a lower 30-min insulin increment (40.8 [34.9–47.6] vs. 58.6 [53.6–64] pmol insulin/mmol glucose, P < 0.001; geometric mean [95% confidence interval]) and a higher plasma insulin level at 120 min (702 [610–808] vs. 444 [400–492] pmol/l, P < 0.001). 32,33 split proinsulin levels were elevated in GDM patients in both fasting (9.1 [7.3–11.4] vs. 6.7 [6.0–7.5] pmol/l, P < 0.02) and 120-min (75.2 [62.9–90.0] vs. 52.2 [46.7–58.3] pmol/l, P < 0.001) samples, respectively. Intact proinsulin levels were significantly elevated at 120 min in the women with GDM (21.3 [18.1–25.1] vs. 14.8 [13.4–16.3] pmol/l, P < 0.001). Thus, the qualitative abnormalities of insulin secretion in GDM patients (low 30-min insulin increment, high 120-min plasma insulin, and elevated 32,33 split proinsulin) are similar to those seen in nonpregnant subjects with impaired glucose tolerance. To determine whether measures of proinsulinlike molecules (PLMs) might assist in the prediction of GDM, women who had a 1-h glucose level of >7.7 mmol/1 after a 50-g glucose challenge at 28–32 weeks’ gestation had insulin and PLMs measured in the 1-h sample. The percentage of total insulin-like molecules accounted for by proinsulin-like molecules (%PLM) was significantly raised in those women in whom a subsequent OGTT showed GDM versus those in whom a later OGTT was normal (13.9 [11.5–16.7] vs. 10.3 [9.6–11.2]% P = 0.003). In a logistic regression analysis, %PLM at screening was more strongly associated with later GDM than age, obesity, the degree of hyperglycemia at screening, or any individual insulin or PLM variable at the screening test. Incorporation of a measure of %PLM in the routine 50-g screening test has the potential for improving the predictive power of screening tests for GDM.

COMPUTERIZED HOME TELEMETRY OF MATERNAL BLOOD PRESSURE IN HYPERTENSIVE PREGNANCY

We have developed a telemetric technique whereby maternal blood pressure, which is self-measured by pregnant women in their own homes using a Dinamap 1846 automated blood pressure recorder, can then be transmitted over the commercial telephone network into the Rosie Maternity Hospital in Cambridge, where it is computer-processed. The maternal blood pressure is then reviewed by the obstetrician as part of the clinical management protocol. We have used this telemetric technique on 90 occasions, from the homes of 10 pregnant hypertensive women. On almost every occasion, the blood pressure measured at home was lower than that previously measured in the hospital antenatal clinic. This technique offers great promise, both in terms of health economics and also in terms of reducing pregnant womens unhappiness about their being admitted to hospital whenever they exhibit moderate to severe hypertension in the antenatal clinic. Indeed, in the antenatal period, home telemetry should allow the vast majority of hypertensive pregnancies to be managed just as safely at home as in hospital. In the management of high risk pregnancy, home telemetry of maternal blood pressure complements three other home telemetric techniques which have already been described: fetal heart rate, maternal blood glucose and uterine contractions.

Application of neural networks to the ranking of perinatal variables influencing birthweight

In this paper we compare Multi-Layer Perceptrons (a neural network type) with Multivariate Linear Regression in predicting birthweight from nine perinatal variables which are thought to be related. Results show, that seven of the nine variables, i.e., gestational age, mothers body-mass index (BMI), sex of the baby, mothers height, smoking, parity and gravidity, are related to birthweight. We found no significant relationship between birthweight and each of the two variables, i.e., maternal age and social class.

Ultradian rhythms in human fetal heart rate: A computerised time series analysis

Even though fetal heart rate recordings are widely used to monitor fetal health, both antenatally and in labour, the underlying physiology is not well understood. For example, it is not known with any certainty whether the oscillations seen in fetal heart rate are highly organised, in reflection of underlying ultradian rhythms, or whether they are entirely random and haphazard. In order to answer this question, therefore, we have used mathematical techniques of time series analysis to look for clear evidence of ultradian rhythms in fetal heart rate recordings. We have found that specific short-term ultradian rhythms are indeed present, and that they can be measured objectively in terms of their frequency, amplitude and phase. Such rhythms have cycle lengths of 10 to 90 s and they can persist for long periods of time. They may also disappear and later reappear, locking back into synchrony again with previous oscillations. Individual rhythms may undergo amplitude change, phase shift, and perhaps even frequency shift.

Objective measurement of anxiety in hypertensive pregnant women managed in hospital and in the community

Objective To determine whether pregnant hypertensives women are more anxious when monitored in hospital or at homes.

Feature selection using expected attainable discrimination

We propose expected attainable discrimination (EAD) as a measure to select discrete valued features for reliable discrimination between two classes of data. EAD is an average of the area under the ROC curves obtained when a simple histogram probability density model is trained and tested on many random partitions of a data set. EAD can be incorporated into various stepwise search methods to determine promising subsets of features, particularly when misclassification costs are difficult or impossible to specify. Experimental application to the problem of risk prediction in pregnancy is described.

Baseline fetal heart rates from 15 to 38 weeks gestation in normotensive and hypertensive pregnancies

Summary. To determine whether the fetal heart behaves differently in normotensive and hypertensive pregnancies, the changes in baseline fetal heart rate were investigated prospectively from 15 to 38 weeks gestation in 16 women who were normotensive at the time of booking in the antenatal clinic. Fetal heart rate recordings were made ultrasonically, and were computer‐processed by the programs TELEPLOT and BASELINE. Those women who remained normotensive exhibited a decrease of fetal heart rate with advancing gestational age, but this did not occur in the six women who eventually developed hypertension.

Fetal home telemetry made simple

SummaryHigh quality fetal home telemetry may be achieved without the help of a computer, using only a simple fetal heart detector at home, the public telephone lines and a conventional fetal heart rate monitor in the obstetric unit. Our system is called HOMEPLOT, and it is inexpensive to install, economical to maintain, simple to use and reliable in operation.

Refusal of interventions to protect the life of the viable fetus--a case-based Transatlantic overview.

Dr Kevin J Dalton LLM FRCOG FCLM Dept Obstetrics & Gynaecology, University of Cambridge, Addenbrooke’s Hospital (Box 223), Cambridge CB2 2QQ, kjd5@cam.ac.uk It is rare for a pregnant woman to refuse a recommended intervention to protect the life of her viable fetus, and few obstetricians have ever come across the problem. Nevertheless, a number of cases of such a refusal have gone to court for resolution, and some have even reached the Supreme Court of the United States. In England such disputes have always been resolved at or below the Court of Appeal. In the United States, federal and state laws are not unanimous on whether the mother’s refusal to accept treatment should always prevail whenever there is a maternal-fetal conflict of interest. By contrast, in English law the matter is at present firmly settled in favour of a competent mother’s right to refuse, on the grounds that respecting her autonomy must always trump the protection of any fetal interest. The question of whether a mother’s refusal to undergo a recommended treatment should be overridden in favour of her viable fetus is fundamentally one of balancing maternal rights against any fetal rights that are recognised by law, or recognised in ethics. But here it is most important to recognise that what may be required or allowed by law may not be required or allowed in an ethical context. The question of fetal rights vis-a-vis maternal rights remains unsettled in law and ethics.