This paper presents a review of decision making in obstetrics. The first section deals with the obstetric problem-solving model, the second general decision theory and finally several aspects of decision making in the domain of obstetrics are examined.

Screening for genetic and congenital abnormalities during pregnancy has developed over the past 10–15 years from a concept to an established aspect of modern obstetric management in response to the declining importance of other causes of infant and perinatal mortality and morbidity. This review will consider why screening is indicated for this group of conditions, the criteria for any screening programme and the current impact of prenatal screening.

The fetus has become increasingly accessible and visible as a patient over the last two decades. Two major technical advances have contributed to the obstetrician's ability to study and understand the fetus. The first advance was electronic fetal heart-rate monitoring, followed by the second major advancement in the form of real time ultrasound. Prior to the introduction of these technologies, biochemical determiniations of oestriol and human placental lactogen were used to monitor fetal wellbeing. Currently the emphasis, both in clinical practice and research protocols, is on biophysical surveillance of the fetus.

The puerperium is a time of substantial maternal risk. Within recent years, crude maternal mortality rates of 8.9/100,000 total births have been reported from England and Wales and of 6.6/100,000 from Sweden. Maternal deaths are considerably more likely to follow delivery than to precede it (Table 1). The risks associated with caesarean section are particularly noteworthy: death rates have been reported to be as much as 12 times greater than those following vaginal delivery.

As a result of advances in perinatal and neonatal care, birth defects now represent an increasing component of the perinatal mortality rate. Approximately 5% of all pregnancies monitored result in an abnormal fetus and close to one-third of these are chromosomal abnormalities. The upsurge of interest in prenatal diagnosis has reflected this increased importance of genetic disorders in obstetrics.

Pregnancy appears to increase the risk of thromboembolism sixfold, but there are wide variations in the reported incidence of thromboembolic complications during pregnancy. This is due to diagnostic difficulties and the inculsion of various clinical entities within the disease classification. However, there are reliable data on the incidence of fatal pulmonary thromboembolism (PTE) due to the detailed and thorough reports of the confidential enquiries into Maternal Deaths in England and Wales.

The established technique of investigating peripheral arteries by continuous-wave Doppler ultrasound was first applied to obstetrics by FitzGerald and Drumm in 1977. Since that time, each year has seen an increasing number of reports regarding obstetric Doppler, but assessment of its true value in pregnancy management, by large prospective randomized trials, is still awaited. Continuous-wave Doppler ultrasound is a relatively simple and inexpensive technique, ideal for screening the uterine and umbilical arterial circulations without the necessity for concurrent ultrasound imaging. However, difficulties in interpretation and analysis of the displayed Doppler-shifted frequencies, as well as the limited number of reports on the performance characteristics of Doppler ultrasound instruments, may well have contributed to the slowness with which the technique has been taken up for study. Continuous-wave Doppler systems designed for obstetric use have recently become available and the Vasoflo-3 (Oxford Sonicaid, Chichester, Sussex) has a microprocessor which makes the instrument very versatile. I shall review the technique of continuous-wave Doppler ultrasound measurement in obstetrics, with particular reference to measurement variation, in the light of our experience with the Vasoflo-3 (Figure 1). I shall then briefly summarize a few of the reports which have used continuous-wave Doppler ultrasound in obstetrics.