Selective fetal growth restriction (sFGR) has been reported to occur in about 10–15% of monochorionic (MC) twins. The diagnosis of sFGR has been based on variable criteria including estimated fetal weight (EFW), abdominal circumference and/or the degree of fetal weight discordance. Recent studies tend to use a simple definition which includes the presence of an EFW less than the 10th percentile in the smaller twin. Some would argue that the intertwin fetal weight discordance should be included in the definition. Indeed this factor plays a major role in the complications presented by these cases. While the majority of cases with one fetus below the 10th percentile usually will also present with a large intertwin EFW discordance, the contrary is not always true. Thus, it is possible to find MC twins with remarkable intertwin EFW discordance but the EFW of both fetuses are still within normal ranges. Although it appears to be common sense that a large intertwin discrepancy might represent a higher risk for some of the complications described later in this review, there is no consistent evidence to support this notion. Therefore, due to its simplicity, a definition based on an EFW below 10th percentile in one twin is probably the most useful for clinical and research purposes.

Congenital cystic adenomatoid malformations of the lung (CCAMs) were originally described by Ch'In and Tang in 1949 as rare lung lesions occurring in premature or stillborn infants with anasarca. In 1977 Stocker et al divided CCAM into three types based on their clinical and pathological features. The nomenclature has since changed to congenital pulmonary airway malformations (CPAMs) to reflect the possible absence of cystic changes and the probable underlying pathogenesis of different types. CPAMs are relatively rare congenital abnormalities with a reported incidence varying from 1 in 10,000 to 1 in 35,000. There is a slight male predominance, but no racial predilection has been noted. This review will outline the current nomenclature and features of different types of CPAMs, highlight possible mechanisms underlying the development of CPAMs, review current antenatal imaging modalities and interventions, address the debate surrounding the postnatal management of CPAMs, and suggest areas for future research.

Almost 80 years ago George Corner and colleagues provided the first evidence that progesterone maintains pregnancy and that it does so, at least in part, by promoting myometrial relaxation. In the 1950s, Arpad Csapo proposed the “progesterone block hypothesis”, which posits that progesterone maintains pregnancy by promoting myometrial relaxation and that its withdrawal initiates a cascade of hormonal interactions that transforms the myometrium to a highly contractile state leading to the onset of labour. Csapo later proposed that contractility of the pregnant myometrium is determined by the balance between relaxation induced by progesterone and contraction induced by a cohort of signals including oestrogens, uterine distention and stimulatory uterotonins such as prostaglandins (PGs) and oxytocin (OT). According to this “seesaw” hypothesis, progesterone promotes myometrial relaxation by directly inducing relaxation and/or by inhibiting the production of, or myometrial responsiveness to, stimulatory uterotonins. These landmark concepts, though derived from studies of experimental animals, form the foundation for current understanding of progesterone's role in the physiology of human pregnancy. Remarkable progress has been made over the last 20–30 years in understanding the signal transduction pathways through which steroid hormones affect target cells. This knowledge has broadened the scope of Csapo's original paradigms and we are now beginning to unravel the specific signaling pathways and molecular interactions by which progesterone affects human myometrium and how its actions are controlled at the functional level. This is important for the development of progestin-based therapeutics for the prevention or suppression of preterm labour and preterm birth. Here we review recent progress in understanding the mechanisms by which progesterone sustains pregnancy and in particular how it promotes myometrial relaxation, how its relaxatory actions are nullified at parturition, and the hormonal interactions that induce progesterone withdrawal to determine the timing of human birth.

Prenatal care reduces the impact of illicit drug use on perinatal outcomes. Women who misuse substances are often excluded from mainstream society and, on becoming pregnant, feel guilty about their drug misuse and the potential effects this could have on their unborn baby. These women are vulnerable in many ways and agencies must ensure that they are not excluded from antenatal care. The latest enquiry into maternal deaths published in the UK (CEMACH report) highlights how women with socially complex lives who died were far less likely to have sought antenatal care early in pregnancy or to remain in regular contact with maternity services. Of the women who died from any cause, 11% had problems with substance abuse of whom 60% were registered addicts. Gaps in communication between agencies was highlighted as a particular problem.

Type 1 diabetes complicates around 1 in 200 to 300 pregnancies in the United Kingdom. Historically maternal type 1 diabetes carried very high risks for mother and child. Introduction of insulin led to an immediate, marked decline in the previously very high rates of maternal mortality; in contrast an improvement in perinatal outcomes occurred more slowly but was nevertheless dramatic. This is strikingly demonstrated by the temporal decline in perinatal mortality in offspring of mothers with type 1 diabetes which was virtually universal before use of insulin in the 1920's, likely remained in excess of 20% even in the 1960's and fell to under 4% by the 1990's. The reasons for this more gradual improvement in perinatal outcomes cannot be defined with precision but will have been influenced by improved glycaemic management with use of intensive, multiple dose insulin treatment and home glucose monitoring; improvements in obstetric and neonatal management, and better management of complications of diabetes before and during pregnancy. In 1989 the St Vincent declaration proposed that pregnancy outcomes in women with type 1 diabetes should approximate those of the non-diabetic population. While the long term improvements in fetal outcomes have been dramatic, contemporary surveys confirm a persistent doubling or more of rates of congenital anomaly and a three to four fold increase in perinatal mortality in the UK and other European countries which will require further clinical innovation to overcome.

Inherited bleeding disorders pose a particular challenge for pregnancy and the puerperium, due to both the inheritance risk to the fetus and the bleeding risk to the mother. Women at risk require counselling to address the following questions

1. 1 Will I bleed?

2. 2 What treatment do I need?

3. 3 Can I pass it on to my children?

Premature birth is the most important cause of perinatal death and long term morbidity in the world today. Although an increasing proportion of premature births are induced secondary to pre-existing fetal and maternal conditions, over half of these deliveries are due to spontaneous onset of uterine contractions (spontaneous preterm labour). So far, our ability to successfully treat women whose pregnancies are complicated by preterm labour is hampered by a lack of knowledge of the endocrine and biochemical factors that initiate human parturition.

Obstetric cholestasis (OC) also known a intrahepatic cholestatsis of pregnancy (ICP) is defined as pruritus of onset in pregnancy in association with abnormal liver function in the absence of any other identifiable liver pathology which resolves on delivery. It may be associated with adverse obstetric outcome and significant maternal morbidity. In the UK the prevalence is thought to be 0.6–0.7%, with up to 39–41% of women with OC being of Indian or Pakistani origin. Higher prevalence is also observed in Scandinavia (2%) and Chile (4%), (especially women of Araucanian Indian descent 24%). The condition occurs more commonly amongst twin pregnancies (20–22%) and is more common in the winter months in both Scandinavian and Chilean populations. The condition may occur more frequently in those >35 years of age (25% of cases).

The topic of pelvic floor assessment is increasingly attracting attention from gynaecologists, colorectal surgeons, urologists and physiotherapists. This is not surprising, many women who have given birth naturally are affected by pelvic floor trauma, and so are their partners. Health professionals deal with the eventual consequences of such trauma, especially pelvic organ prolapse and faecal incontinence.

Much of our current understanding of human gestation is largely based on information extracted from animal and cell models. Although this information has been fundamental for progression of reproductive research, much of it examines biological molecules in isolation rather than the integrated manner in which they function. Disruption to these fundamental processes is the source of pregnancy complications, of which for many (including pre-eclampsia) the exact aetiology has not been fully elucidated. We need to re-examine the limited way by which we approach these problems, and aim to understand pathophysiology in a more inclusive/holistic way.

The third stage of labour is defined as the period following the completed delivery of the newborn until the completed delivery of the placenta and its attached membranes. Whilst to the exhausted labouring woman this stage may be an afterthought, it is a crucial time for fetal-to-neonatal transition. Major changes in anatomy and physiology occur in both mother and baby. It has also been described as ‘potentially the most hazardous part of childbirth, largely due to the risk of postpartum haemorrhage (PPH) on placental separation. Despite this, the current management guidelines are based on an ‘eclectic combination of historical, anecdotal, philosophical and research-based factors.

The determination of individual preference or choice for a new product, and satisfaction with an existing product or service are routinely performed by advertising and market survey companies worldwide. The data collected, once analysed, has allowed companies to determine the attributes consumers desire within their, or a competitor's, existing products and services. In this way they are able to identify possible ways to improve their products and services and thus to use their own resources efficiently and effectively, thereby maximising their returns for the expenditure incurred.

There is little doubt that congenital abnormalities cause significant stresses to the affected children, their parents and the whole family. Such stresses can be physical, psychological, social and financial. To society, the cost of looking after these affected individuals properly can be substantial. In the absence of prenatal screening, birth defects affect approximately 2–4% of newborns, although there are significant variations between populations.

There has been a marked increase in the prevalence of twins, triplets and higher-order multiple pregnancies over the last 20 years due, in part, to delayed childbearing, but more significantly associated with the widespread introduction of assisted reproductive techniques. Once viability is confirmed these pregnancies pose a series of unique challenges to the obstetrician as the dynamic of the maternal – fetal relationship changes when there are two, or more, fetuses to consider. With the exception of postmaturity, all obstetric complications are more common in multiple pregnancies. Australian data shows perinatal mortality rates of 7, 25 and 63 per 1,000 births for singleton, twin (RR 3.4) and triplet (RR 8.5) pregnancies respectively; with similar rates reported in the UK and USA. While multiple pregnancies account for only 2% of births, they account for 20% of neonatal admissions and 12% of perinatal deaths – with a 5-fold increase in deaths before 1 year of age.

The management of congenital diaphragmatic hernia (CDH) in the newborn infant has changed radically since the first successful outcomes were reported 60 years ago. Then it seemed a surgical problem with a surgical solution – do an operation, remove the intestines and solid viscera from the thoracic cavity, repair the defect and allow the lung to expand. CDH in that era was regarded as the quintessential neonatal surgical emergency. The expectation was that urgent surgery would result in improvement in lung function and oxygenation. That approach persisted up to the 1980s when it was realized that the problem was far more complex and involved both an abnormal pulmonary vascular bed as well as pulmonary hypoplasia. The use of systemically delivered pulmonary vasodilator therapy, principally tolazoline, became a focus of interest in the 1980s with small case reports and case series suggesting improved survival. In the 1990s, based on studies that showed worsening thoracic compliance and gas exchange following surgical repair, deferred surgery and pre-operative stabilization became the standard of care. At the same time extracorporeal membrane oxygenation (ECMO) was increasingly used either as part of pre-operative stabilization or as a rescue therapy after repair. Other centres chose to use high frequency oscillatory ventilation (HFOV). Despite all these innovations the survival in live born infants with CDH did not improve to more than 50% in large series published from high volume centres. However, in the past 10 years there has been an appreciable improvement in survival to the extent that many centres are now reporting survival rates of greater than 80%. Probably the biggest impact on this improvement has been the recognition of the role that ventilation induced lung injury plays in mortality and the need for ECMO rescue. This has ushered in an era of a lung protective or “gentle ventilation” strategy which has been widely adopted as a standard approach. While there have been these radical changes in postnatal management attempts have been made to improve outcome with prenatal interventions, starting with prenatal repair, which was abandoned because of preterm labour. More recently there has been increasing experience in the use of balloon occlusion of the trachea as a prenatal intervention strategy with patients being selected based on prenatal predictors of poor outcome. This approach can only be justified if those predictors can be validated and the outcomes (death or serious long term morbidity) can be shown to be better than those currently achievable, namely 80% survival in high volume CDH centres rather than the 50–60% survival frequently quoted in historical papers.

Parturition is the process leading to expulsion of the fetus from the uterus. It is the result of a co-ordinated interplay between maternal and fetal factors. Despite extensive research the mechanisms that control the length of human pregnancy and signal the onset of labour remain unknown. Preterm labour refers to the onset of labour before 37 completed weeks or 259 days of pregnancy and after the gestation of viability (20–25 weeks, depending on definition). In most developed countries, preterm birth occurs in 5–10% of pregnancies whereas this may rise to 25% in certain developing countries. Despite advancing knowledge of risk factors and the introduction of beneficial medical and public health interventions the incidence of preterm birth rate has risen over the last two decades. Preterm birth is the single biggest cause of perinatal mortality. Adverse outcomes for the neonate include respiratory complications, necrotizing enterocolitis, sepsis and neurodevelopmental disorders. Among those babies born before 30 weeks who survive, approximately 25% will have a major disability. Another 10% will have some disability and an additional 30% will have cognitive, perceptual and behavioural problems that could interfere with school performance. The consequences of prematurity are not confined to the neonate but have important long-term social, financial, behavioural and educational implications.