Bailliere's clinical obstetrics and gynaecology最新文献

Ultrasound imaging techniques, both transabdominal and transvaginal, are the most accurate and widely used imaging modalities in the detection and characterization of uterine leiomyomas. The diagnosis of these tumours may be enhanced using ultrasound-guided uterine biopsy and hysterosonography. Magnetic resonance imaging provides accurate imaging information, but its cost and lack of significant superiority over ultrasound have hitherto limited its use. Computerized tomography, plain X-ray, and hysterosalpingography have little to offer in the assessment of fibroids.

High-order multiples are increasingly common as a result of assisted reproductive technologies and represent pregnancies at exceptional risk. This article discusses the antepartum management of high-order multiples, which has in general been highly individualized and poorly studied. Care for high-order multiples should include preterm birth prevention education, the frequent assessment of maternal symptoms and cervical status by a consistent provider, individualized modification of activity, attention to maternal nutrition, ultrasonography for the assessment of fetal anatomy and intra-uterine growth and anticipation of maternal complications. Interventions such as prophylactic cerclage, uterine activity monitoring, prophylactic tocolysis or hospitalization have not improved outcome when used routinely, and guidelines for selective use will be presented. Specialized care for high-order multiples should be directed at identifying congenital anomalies, maximizing fetal growth and preventing early preterm birth, the effect of which will be to improve perinatal outcome for these exceptional pregnancies.

Monochorionic (MC) placentation occurs in two-thirds of monozygous twins and approximately 0.3% of all spontaneous conceptions. Vascular anastomoses within the placenta allow intertwin transfusion to occur, which is in most cases a normal event. However, imbalance in this flow may lead to the clinical sequelae observed, with acute, chronic or reverse intertwin transfusion. Acute transfusion describes the events following the death of one of an MC twin pair in utero, with an approximately 1 in 4 chance of demise or neurological damage in the co-twin. Chronic intertwin transfusion, otherwise termed feto-fetal transfusion syndrome, arises following the gradual flux of blood from one twin (the donor) to its sibling fetus (the recipient). The ensuing polyhydramnios places the pregnancy at risk of preterm amniorrhexis and/or labour, notwithstanding the specific sequelae seen in these fetuses following chronic in utero insult. Reverse transfusion describes the most bizarre form of intertwin transfusion: acardiac twinning. Retrograde perfusion of one of the twins with deoxygenated blood leads to the formation of a non-viable acardiac parasite and a ‘pump twin’ struggling to maintain the cardiac output required to perfuse both twins.

All assisted conception techniques are associated with an increase in the multiple pregnancy rate. Iatrogenic multiple births are increasing as the use of these technologies expands. The cornerstone of safe ovulation induction is careful ultrasound monitoring, with cancellation of cycles if excessive ovulation is expected. In in vitro fertilization (IVF) cycles, the main determinant of multiple pregnancy risk is the number of embryos replaced. The current move in IVF clinics is to reduce the risk of multiple pregnancy by reducing the number of embryos transferred. We would suggest a maximum of two embryos transferred to women under, for example, 39 years of age. Women of 39 years or over have a reduced chance of embryo implantation; they should be allowed the transfer of up to three embryos (the UK legal maximum).

This chapter aims to provide a current review of the use of Doppler ultrasound in the management of multiple pregnancies. OVID and Medline searches were undertaken. Randomized controlled trials, where available, were assessed by the Cochrane Review Manager (RevMan-version 3.0). The specific multiple pregnancy problems of fetal growth restriction (FGR), twin reversed arterial perfusion sequence and twin-twin transfusion syndrome (TTTS) were also reviewed. Historically, controlled and randomized controlled trials show a promising reduction in perinatal mortality in twin pregnancies where Doppler ultrasound is used. However, the numbers are small and further trials are recommended. In those twin pregnancies in which there is FGR as a result of placental dysfunction, Doppler ultrasonography will show intertwin discordancy. In those twin pairs where development is complicated by TTTS, there is often discordant fetal size, with concordant fetal Doppler results. Thus Doppler ultrasound appears to be useful in the management of twin pregnancies and in delineating those complicated by FGR and TTTS.

There is increasing interest in the outcomes of multiple pregnancies as their numbers rise, mainly owing to advances in fertility-enhancing techniques. In addition, the numbers of multiple births surviving the perinatal period is increasing with the increasing survival of very tiny babies. In order to investigate these outcomes or to evaluate procedures that may improve them, it is important to consider a number of methodological issues that affect the comparability of data both between and within populations. How a birth and a multiple birth are defined, data sources, whether multiple pregnancies or individual births are being counted and the identification of multiple gestations by zygosity and chorionicity will all affect the reported outcome rates. In light of this, perinatal mortality and neurodevelopmental disabilities are examined as adverse outcomes of multiple pregnancies.

Multiple gestations account for 1–2% of all pregnancies but contribute disproportionately to the incidence of both perinatal loss and fetal structural abnormalities. Ultrasound examination provides essential information about screening for, and the management of, such defects, including accurate determination of chorionicity, assessment of risk, invasive testing and selective termination if appropriate.

Various methods of predicting preterm labour in both singleton and multiple pregnancies have been studied including risk scoring systems, home uterine activity monitoring, cervical assessment and biochemical methods. In practice, risk scoring systems for preterm delivery perform poorly. Consensus in the literature regarding the usefulness of home uterine activity monitoring is lacking and well designed randomized controlled trials are required. Transvaginal ultrasound assessment of the cervix appears to have a role to play in the prediction of preterm labour. The presence of IFN in cervicovaginal fluid in the late second and early third trimesters is an important risk factor for preterm labour in asymptomatic women with multiple pregnancies. Preterm labour may be mediated in part by inflammatory cytokines. The measurement of these inflammatory cytokines in cervical secretions may also prove helpful in the prediction of preterm labour. It is anticipated that an improved ability to predict preterm labour in both singleton and multiple pregnancies will depend on increasing understanding of the condition's pathophysiology

Multifetal pregnancy reduction (MFPR) has become a mainstay of infertility therapy as its development has allowed physicians to become more aggressive in treating patients resistant to more conservative therapies. Over the course of the past decade, MFPR has become practised in a limited number of tertiary specialty centres, which have improved its performance and very substantially lowered its risks. The majority of physicians performing MFPR employ a transabdominal needle injection of potassium chloride into the fetal thorax. Risks for pregnancy losses of patients starting with triplets and/or quadruplets reduced to twins have improved over the past decade and are not substantially different from those in patients whose pregnancy began as twins. There have been no substantiated risks of coagulopathies or damage to surviving fetuses.