Comparing methods of analysing datasets with small clusters: case studies using four paediatric datasets

Studies of prematurely born infants contain a relatively large percentage of multiple births, so the resulting data have a hierarchical structure with small clusters of size 1, 2 or 3. Ignoring the clustering may lead to incorrect inferences. The aim of this study was to compare statistical methods which can be used to analyse such data: generalised estimating equations, multilevel models, multiple linear regression and logistic regression. Four datasets which differed in total size and in percentage of multiple births (n = 254, multiple 18%; n = 176, multiple 9%; n = 10 098, multiple 3%; n = 1585, multiple 8%) were analysed. With the continuous outcome, two-level models produced similar results in the larger dataset, while generalised least squares multilevel modelling (ML GLS 'xtreg' in Stata) and maximum likelihood multilevel modelling (ML MLE 'xtmixed' in Stata) produced divergent estimates using the smaller dataset. For the dichotomous outcome, most methods, except generalised least squares multilevel modelling (ML GH 'xtlogit' in Stata) gave similar odds ratios and 95% confidence intervals within datasets. For the continuous outcome, our results suggest using multilevel modelling. We conclude that generalised least squares multilevel modelling (ML GLS 'xtreg' in Stata) and maximum likelihood multilevel modelling (ML MLE 'xtmixed' in Stata) should be used with caution when the dataset is small. Where the outcome is dichotomous and there is a relatively large percentage of non-independent data, it is recommended that these are accounted for in analyses using logistic regression with adjusted standard errors or multilevel modelling. If, however, the dataset has a small percentage of clusters greater than size 1 (e.g. a population dataset of children where there are few multiples) there appears to be less need to adjust for clustering.

Treatment of asphyxiated newborns with moderate hypothermia in routine clinical practice: how cooling is managed in the UK outside a clinical trial

BACKGROUND

This is a phase 4 study of infants registered with the UK TOBY Cooling Register from December 2006 to February 2008. The registry was established on completion of enrolLment to the TOBY randomised trial of treatment with whole body hypothermia following perinatal asphyxia at the end of November 2006.

METHODS

We collected information about patient characteristics, condition at birth, resuscitation details, severity of encephalopathy, hourly temperature record, clinical complications and outcomes before hospital discharge.

RESULTS

120 infants born at a median of 40 (IQR 38-41) weeks' gestation and weighing a median of 3287 (IQR 2895-3710) g at birth were studied. Cooling was started at a median of 3 h 54 min (IQR 2 h-5 h 32 min) after birth. All but three infants underwent whole body cooling. The mean (SD) rectal temperature from 6 to 72 h of the cooling period was 33.57 degrees C (0.51 degrees C). The daily encephalopathy score fell: median (IQR) 11 (6-15), 9.7 (5-14), 8 (5-13) and 7 (2-12) on days 1-4 after birth, respectively. 51% of the infants established full oral feeding at a median (range) of 9 (4-24) days. 26% of the study infants died. MRI was consistent with hypoxia-ischaemia in most cases. Clinical complications were not considered to be due to hypothermia.

CONCLUSION

In the UK, therapeutic hypothermia following perinatal asphyxia is increasingly being provided. The target body temperature is successfully achieved and the clinical complications observed were not attributed to hypothermia. Treatment with hypothermia may have prevented the worsening of the encephalopathy that is commonly observed following asphyxia.

Tuberculosis in pregnancy in the UK

Tuberculosis (TB) is a globally important cause of morbidity and mortality with an increasing incidence in women of reproductive ages. This descriptive study using the UK Obstetric Surveillance System demonstrates key differences in the presentation of TB during pregnancy compared with the nonpregnant population. The disease is limited to ethnic minority women, most commonly recent immigrants. Presentation may be atypical, with extrapulmonary disease as common as pulmonary. Clinicians should be aware of the potential for nonspecific presentation of the disease in pregnancy and consider the diagnosis in women, especially recently arrived immigrants, presenting with nonspecific symptoms.

Inequalities in maternal health: national cohort study of ethnic variation in severe maternal morbidities

OBJECTIVE

To describe on a national basis ethnic differences in severe maternal morbidity in the United Kingdom.

DESIGN

National cohort study using the UK Obstetric Surveillance System (UKOSS).

SETTING

All hospitals with consultant led maternity units in the UK.

PARTICIPANTS

686 women with severe maternal morbidity between February 2005 and February 2006.

MAIN OUTCOME MEASURES

Rates, risk ratios, and odds ratios of severe maternal morbidity in different ethnic groups.

RESULTS

686 cases of severe maternal morbidity were reported in an estimated 775 186 maternities, representing an estimated incidence of 89 (95% confidence interval 82 to 95) cases per 100 000 maternities. 74% of women were white, and 26% were non-white. The estimated risk of severe maternal morbidity in white women was 80 cases per 100 000 maternities, and that in non-white women was 126 cases per 100,000 (risk difference 46 (27 to 66) cases per 100 000; risk ratio 1.58, 95% confidence interval 1.33 to 1.87). Black African women (risk difference 108 (18 to 197) cases per 100,000 maternities; risk ratio 2.35, 1.45 to 3.81) and black Caribbean women (risk difference 116 (59 to 172) cases per 100 000 maternities; risk ratio 2.45, 1.81 to 3.31) had the highest risk compared with white women. The risk in non-white women remained high after adjustment for differences in age, socioeconomic and smoking status, body mass index, and parity (odds ratio 1.50, 1.15 to 1.96).

CONCLUSIONS

Severe maternal morbidity is significantly more common among non-white women than among white women in the UK, particularly in black African and Caribbean ethnic groups. This pattern is very similar to reported ethnic differences in maternal death rates. These differences may be due to the presence of pre-existing maternal medical factors or to factors related to care during pregnancy, labour, and birth; they are unlikely to be due to differences in age, socioeconomic or smoking status, body mass index, or parity. This highlights to clinicians and policy makers the importance of tailored maternity services and improved access to care for women from ethnic minorities. National information on the ethnicity of women giving birth in the UK is needed to enable ongoing accurate study of these inequalities.

Cytokine gene polymorphisms in preterm infants with necrotising enterocolitis: genetic association study

BACKGROUND

The inflammatory cytokine cascade is implicated in the pathogenesis of necrotising enterocolitis (NEC). Genetic association studies of cytokine polymorphisms may help to detect molecular mechanisms that are causally related to the disease process.

AIM

To examine associations between the common genetic variants in candidate inflammatory cytokine genes and NEC in preterm infants.

METHODS

Multi-centre case-control and genetic association study. DNA samples were collected from 50 preterm infants with NEC and 50 controls matched for gestational age and ethnic group recruited to a multi-centre case-control study. Ten candidate single-nucleotide polymorphisms in cytokines previously associated with infectious or inflammatory diseases were genotyped. The findings were included in random-effects meta-analyses with data from previous genetic association studies.

RESULTS

All allele distributions were in Hardy-Weinberg equilibrium. None of the studied cytokine polymorphisms was significantly associated with NEC. Four previous genetic association studies of cytokine polymorphisms and NEC in preterm infants were found. Meta-analyses were possible for several single-nucleotide polymorphisms. These increased the precision of the estimates of effect size but did not reveal any significant associations.

CONCLUSIONS

The available data are not consistent with more than modest associations between these candidate cytokine variant alleles and NEC in preterm infants. Data from future association studies of these polymorphisms may be added to the meta-analyses to obtain more precise estimates of effects sizes.

Enteral feeding regimens and necrotising enterocolitis in preterm infants: a multicentre case-control study

BACKGROUND

Most preterm infants who develop necrotising enterocolitis (NEC) have received enteral feeds. Uncertainty exists about which aspects of the feeding regimen affect the risk of NEC.

AIM

To examine associations between various enteral feeding practices and the development of NEC in preterm infants.

METHODS

Multicentre case-control study. 53 preterm infants with NEC were enrolled together with a gestational age frequency-matched control without NEC from a randomly selected neonatal unit. Clinical and feeding data were extracted and compared between the groups.

RESULTS

Significantly fewer cases than controls had received human breast milk (75% vs 91%; OR 0.32, 95% CI 0.11 to 0.98). The day on which enteral feeding was started did not differ significantly (mean (SD) days after birth: cases 2.9 (2.8) and controls 2.8 (1.8)). The mean (SD) duration of trophic feeding (<1 ml/kg/h) was significantly shorter in the cases (3.3 (3.1) days) than controls (6.2 (6.7) days) (mean difference (MD) -2.9, 95% CI -4.9 to -0.9) days. Cases were fully fed significantly earlier than controls (mean (SD) days after birth: cases 9.9 (4.2) and controls 14.3 (9.8); MD -4.4, 95% CI -7.3 to -1.5).

CONCLUSIONS

These data suggest that the duration of trophic feeding and rate of advancement of feed volumes may be modifiable risk factors for NEC in preterm infants. Further randomised controlled trials are warranted to assess the effect of different rates of feed advancement on the incidence of NEC, as well as other outcomes.

Granulocyte-macrophage colony stimulating factor administered as prophylaxis for reduction of sepsis in extremely preterm, small for gestational age neonates (the PROGRAMS trial): a single-blind, multicentre, randomised controlled trial

BACKGROUND

Systemic sepsis is a major cause of death in preterm neonates. There are compelling theoretical reasons why treatment with haemopoietic colony-stimulating factors might reduce sepsis and improve outcomes, and as a consequence these agents have entered into use in neonatal medicine without adequate evidence. We assessed whether granulocyte-macrophage colony stimulating factor (GM-CSF) administered as prophylaxis to preterm neonates at high risk of neutropenia would reduce sepsis, mortality, and morbidity.

METHODS

We undertook a single-blind, multicentre, randomised controlled trial in 26 centres between June, 2000, and June, 2006. 280 neonates of below or equal to 31 weeks' gestation and below the 10th centile for birthweight were randomised within 72 h of birth to receive GM-CSF 10 microg/kg per day subcutaneously for 5 days or standard management. From recruitment to day 28 a detailed daily clinical record form was completed by the treating clinicians. Primary outcome was sepsis-free survival to 14 days from trial entry. Analysis was by intention to treat. This study is registered as an International Standard Randomised Controlled Trial, number ISRCTN42553489.

FINDINGS

Neutrophil counts after trial entry rose significantly more rapidly in infants treated with GM-CSF than in control infants during the first 11 days (difference between neutrophil count slopes 0.34 x 10(9)/L/day; 95% CI 0.12-0.56). There was no significant difference in sepsis-free survival for all infants (93 of 139 treated infants, 105 of 141 control infants; difference -8%, 95% CI -18 to 3). A meta-analysis of this trial and previous published prophylactic trials showed no survival benefit.

INTERPRETATION

Early postnatal prophylactic GM-CSF corrects neutropenia but does not reduce sepsis or improve survival and short-term outcomes in extremely preterm neonates.

Childhood outcomes after prescription of antibiotics to pregnant women with preterm rupture of the membranes: 7-year follow-up of the ORACLE I trial

BACKGROUND

The ORACLE I trial compared the use of erythromycin and/or amoxicillin-clavulanate (co-amoxiclav) with that of placebo for women with preterm rupture of the membranes without overt signs of clinical infection, by use of a factorial randomised design. The aim of the present study--the ORACLE Children Study I--was to determine the long-term effects on children of these interventions.

METHODS

We assessed children at age 7 years born to the 4148 women who had completed the ORACLE I trial and who were eligible for follow-up with a structured parental questionnaire to assess the child's health status. Functional impairment was defined as the presence of any level of functional impairment (severe, moderate, or mild) derived from the mark III Multi-Attribute Health Status classification system. Educational outcomes were assessed with national curriculum test results for children resident in England.

FINDINGS

Outcome was determined for 3298 (75%) eligible children. There was no difference in the proportion of children with any functional impairment after prescription of erythromycin, with or without co-amoxiclav, compared with those born to mothers who received no erythromycin (594 [38.3%] of 1551 children vs 655 [40.4%] of 1620; odds ratio 0.91, 95% CI 0.79-1.05) or after prescription of co-amoxiclav, with or without erythromycin, compared with those born to mothers who received no co-amoxiclav (645 [40.6%] of 1587 vs 604 [38.1%] of 1584; 1.11, 0.96-1.28). Neither antibiotic had a significant effect on the overall level of behavioural difficulties experienced, on specific medical conditions, or on the proportions of children achieving each level in reading, writing, or mathematics at key stage one.

INTERPRETATION

The prescription of antibiotics for women with preterm rupture of the membranes seems to have little effect on the health of children at 7 years of age.

FUNDING

UK Medical Research Council.

Childhood outcomes after prescription of antibiotics to pregnant women with spontaneous preterm labour: 7-year follow-up of the ORACLE II trial

BACKGROUND

The ORACLE II trial compared the use of erythromycin and/or amoxicillin-clavulanate (co-amoxiclav) with that of placebo for women in spontaneous preterm labour and intact membranes, without overt signs of clinical infection, by use of a factorial randomised design. The aim of the present study--the ORACLE Children Study II--was to determine the long-term effects on children after exposure to antibiotics in this clinical situation.

METHODS

We assessed children at age 7 years born to the 4221 women who had completed the ORACLE II study and who were eligible for follow-up with a structured parental questionnaire to assess the child's health status. Functional impairment was defined as the presence of any level of functional impairment (severe, moderate, or mild) derived from the mark III Multi-Attribute Health Status classification system. Educational outcomes were assessed with national curriculum test results for children resident in England.

FINDINGS

Outcome was determined for 3196 (71%) eligible children. Overall, a greater proportion of children whose mothers had been prescribed erythromycin, with or without co-amoxiclav, had any functional impairment than did those whose mothers had received no erythromycin (658 [42.3%] of 1554 children vs 574 [38.3%] of 1498; odds ratio 1.18, 95% CI 1.02-1.37). Co-amoxiclav (with or without erythromycin) had no effect on the proportion of children with any functional impairment, compared with receipt of no co-amoxiclav (624 [40.7%] of 1523 vs 608 [40.0%] of 1520; 1.03, 0.89-1.19). No effects were seen with either antibiotic on the number of deaths, other medical conditions, behavioural patterns, or educational attainment. However, more children whose mothers had received erythromycin or co-amoxiclav developed cerebral palsy than did those born to mothers who received no erythromycin or no co-amoxiclav, respectively (erythromycin: 53 [3.3%] of 1611 vs 27 [1.7%] of 1562, 1.93, 1.21-3.09; co-amoxiclav: 50 [3.2%] of 1587 vs 30 [1.9%] of 1586, 1.69, 1.07-2.67). The number needed to harm with erythromycin was 64 (95% CI 37-209) and with co-amoxiclav 79 (42-591).

INTERPRETATION

The prescription of erythromycin for women in spontaneous preterm labour with intact membranes was associated with an increase in functional impairment among their children at 7 years of age. The risk of cerebral palsy was increased by either antibiotic, although the overall risk of this condition was low.

FUNDING

UK Medical Research Council.

A prospective national study of acute fatty liver of pregnancy in the UK

OBJECTIVES

To identify a national, population-based cohort of women with acute fatty liver of pregnancy (AFLP), to evaluate proposed diagnostic criteria and to document accurately the incidence, management and outcomes of the condition.

SUBJECTS AND METHODS

This was a population-based descriptive study using the UK Obstetric Surveillance System, carried out in all 229 hospitals with consultant-led maternity units in the UK. The participants comprised 57 women in the UK diagnosed with AFLP between February 2005 and August 2006 in an estimated cohort of 1 132 964 maternities (women delivering).

RESULTS

The estimated incidence of AFLP was 5.0 cases per 100 000 maternities (95% CI 3.8 to 6.5 per 100,000). Fifty-five cases (90%) were confirmed by diagnostic criteria and clinical assessment, two (3%) by clinical assessment alone, representing 97% agreement (kappa statistic = 0.78). 18% of women had twin pregnancies and 20% were underweight (body mass index (BMI) <20). 60% of women were admitted to intensive care and 15% to a specialist liver unit. One woman received a liver transplant. One woman died (case fatality rate 1.8%, 95% CI 0% to 9.4%). There were seven deaths among 67 infants (perinatal mortality rate 104 per 1000 births, 95% CI 43 to 203).

CONCLUSIONS

The largest population-based cohort of women with AFLP to date has been identified. Diagnostic criteria previously proposed agree substantially with clinical diagnosis. The incidence estimate from this study is lower than documented by earlier hospital-based studies, but maternal and neonatal outcomes are better than previously reported, possibly related to improved ascertainment. Women with twin pregnancies appear to be at higher risk, but further studies are needed to investigate the risk associated with low BMI.

The TOBY Study. Whole body hypothermia for the treatment of perinatal asphyxial encephalopathy: a randomised controlled trial

Background

A hypoxic-ischaemic insult occurring around the time of birth may result in an encephalopathic state characterised by the need for resuscitation at birth, neurological depression, seizures and electroencephalographic abnormalities. There is an increasing risk of death or neurodevelopmental abnormalities with more severe encephalopathy. Current management consists of maintaining physiological parameters within the normal range and treating seizures with anticonvulsants.

Studies in adult and newborn animals have shown that a reduction of body temperature of 3–4°C after cerebral insults is associated with improved histological and behavioural outcome. Pilot studies in infants with encephalopathy of head cooling combined with mild whole body hypothermia and of moderate whole body cooling to 33.5°C have been reported. No complications were noted but the group sizes were too small to evaluate benefit.

Methods/Design

TOBY is a multi-centre, prospective, randomised study of term infants after perinatal asphyxia comparing those allocated to "intensive care plus total body cooling for 72 hours" with those allocated to "intensive care without cooling".

Full-term infants will be randomised within 6 hours of birth to either a control group with the rectal temperature kept at 37 +/- 0.2°C or to whole body cooling, with rectal temperature kept at 33–34°C for 72 hours. Term infants showing signs of moderate or severe encephalopathy +/- seizures have their eligibility confirmed by cerebral function monitoring. Outcomes will be assessed at 18 months of age using neurological and neurodevelopmental testing methods.

Sample size

At least 236 infants would be needed to demonstrate a 30% reduction in the relative risk of mortality or serious disability at 18 months.

Recruitment was ahead of target by seven months and approvals were obtained allowing recruitment to continue to the end of the planned recruitment phase. 325 infants were recruited.

Primary outcome

Combined rate of mortality and severe neurodevelopmental impairment in survivors at 18 months of age. Neurodevelopmental impairment will be defined as any of:

• Bayley mental developmental scale score less than 70

• Gross Motor Function Classification System Levels III – V

• Bilateral cortical visual impairments

Trial Registration

Current Controlled Trials ISRCTN89547571

MRC ORACLE Children Study. Long term outcomes following prescription of antibiotics to pregnant women with either spontaneous preterm labour or preterm rupture of the membranes

Background

The Medical Research Council (MRC) ORACLE trial evaluated the use of co-amoxiclav 375 mg and/or erythromycin 250 mg in women presenting with preterm rupture of membranes (PROM) ORACLE I or in spontaneous preterm labour (SPL) ORACLE II using a factorial design. The results showed that for women with a singleton baby with PROM the prescription of erythromycin is associated with improvements in short term neonatal outcomes, although co-amoxiclav is associated with prolongation of pregnancy, a significantly higher rate of neonatal necrotising enterocolitis was found in these babies. Prescription of erythromycin is now established practice for women with PROM. For women with SPL antibiotics demonstrated no improvements in short term neonatal outcomes and are not recommended treatment. There is evidence that both these conditions are associated with subclinical infection so perinatal antibiotic administration may reduce the risk of later disabilities, including cerebral palsy, although the risk may be increased through exposure to inflammatory cytokines, so assessment of longer term functional and educational outcomes is appropriate.

Methods

The MRC ORACLE Children's Study will follow up UK children at age 7 years born to 4809 women with PROM and the 4266 women with SPL enrolled in the earlier ORACLE trials. We will use a parental questionnaire including validated tools to assess disability and behaviour. We will collect the frequency of specific medical conditions: cerebral palsy, epilepsy, respiratory illness including asthma, diabetes, admission to hospital in last year and other diseases, as reported by parents.

National standard test results will be collected to assess educational attainment at Key Stage 1 for children in England.

Discussion

This study is designed to investigate whether or not peripartum antibiotics improve health and disability for children at 7 years of age.

Trial registration

The ORACLE Trial and Children Study is registered in the Current Controlled Trials registry. ISCRTN 52995660

Vaginal microbicides for preventing mother-to-child transmission of HIV infection--no evidence of an effect or evidence of no effect?

BACKGROUND

Vaginal disinfection is a simple, potentially effective strategy for reducing mother-to-child transmission (MTCT) of HIV that can be implemented in combination with antiretroviral therapy or even in the absence of prenatal HIV testing. We systematically reviewed currently available randomised controlled trials to estimate the benefits and risks of this intervention.

METHODS

We conducted an exhaustive search for published and unpublished trials assessing the effect of vaginal microbicides on MTCT of HIV, extracted data in triplicate, assessed statistical heterogeneity between trial results, and conducted meta-analysis using Mantel-Haenszel's method.

FINDINGS

Five potentially eligible studies were identified, two of which met eligibility criteria. Pooling the data shows that the effect of vaginal disinfection on the risk of MTCT of HIV (relative risk (RR) 0.94, 95% confidence interval (CI) 0.71 - 1.25) and neonatal death (RR 1.36, 95% CI 0.32 - 5.79) is uncertain. The combined data (two trials with 708 participants) had less than 80% power to detect a 30% reduction in the risk of MTCT of HIV from a baseline risk of 30%, and are compatible with a wide range of effects; from a 29% reduction to a 25% increase in risk. One trial, with 108 participants, showed no evidence that adverse effects increased in mothers (RR 1.02, 95% CI 0.87 - 1.20) and found that adverse effects decreased in neonates (RR 0.45, 95% CI 0.32 - 0.64).

INTERPRETATION

At present there is insufficient and inconclusive evidence on the effect of vaginal microbicides on the risk of MTCT of HIV. This review identifies the need and provides the impetus for an adequately powered randomised controlled trial to assess the effect(s) of this inexpensive intervention.

Variations in policies for management of the third stage of labour and the immediate management of postpartum haemorrhage in Europe

BACKGROUND

The EUropean Project on obstetric Haemorrhage Reduction: Attitudes, Trial, and Early warning System (EUPHRATES) is a set of five linked projects, the first component of which was a survey of policies for management of the third stage of labour and immediate management of postpartum haemorrhage following vaginal birth in Europe.

OBJECTIVES

The objectives were to ascertain and compare policies for management of the third stage of labour and immediate management of postpartum haemorrhage in maternity units in Europe following vaginal birth.

DESIGN

Survey of policies.

SETTING

The project was a European collaboration, with participants in 14 European countries.

SAMPLE

All maternity units in 12 countries and in selected regions of two countries in Europe.

METHODS

A postal questionnaire was sent to all or a defined sample of maternity units in each participating country.

MAIN OUTCOME MEASURES

Stated policies for management of the third stage of labour and the immediate management of postpartum haemorrhage.

RESULTS

Policies of using uterotonics for the management of the third stage were widespread, but policies about agents, timing, clamping and cutting the umbilical cord and the use of controlled cord traction differed widely. For immediate management of postpartum haemorrhage, policies of massaging the uterus were widespread. Policies of catheterising the bladder, bimanual compression and in the choice of drugs administered were much more variable.

CONCLUSIONS

Considerable variations were observed between and within countries in policies for management of the third stage of labour. Variations were observed, but to a lesser extent, in policies for the immediate management of postpartum haemorrhage after vaginal birth. In both cases, policies about the pharmacological agents to be used varied widely.

Donor breast milk versus infant formula for preterm infants: systematic review and meta-analysis

OBJECTIVES

To compare the effect of donor breast milk with infant formula in preterm infants. Separate comparisons with formula were made for donor breast milk that was: (1) given as a sole diet; (2) given as a supplement to mother's own breast milk; and (3) fortified with macronutrients and micronutrients. The main outcomes were death, necrotising enterocolitis (NEC), infection, growth and development.

DATA SOURCES

Electronic databases-Cochrane, CENTRAL, MEDLINE, EMBASE, CINAHL, and HMIC: DH.

REVIEW METHODS

Systematic review and meta-analysis of trials and observational studies of preterm or low birthweight infants.

RESULTS

Seven studies (including five randomised controlled trials), all from the 1970s and 1980s, fulfilled the inclusion criteria. All studies compared the effect of sole donor breast milk with formula (combined n = 471). One of these also compared the effect of donor breast milk with formula given as a supplement to mother's own milk (n = 343). No studies examined fortified donor breast milk. A meta-analysis based on three studies found a lower risk of NEC in infants receiving donor breast milk compared with formula (combined RR 0.21, 95% CI 0.06 to 0.76). Donor breast milk was associated with slower growth in the early postnatal period, but its long-term effect is unclear.

CONCLUSION

Donor breast milk is associated with a lower risk of NEC and slower growth in the early postnatal period, but the quality of the evidence is limited. Further research is needed to confirm these findings and measure the effect of fortified or supplemented donor breast milk.

Systematic review of effects of low-moderate prenatal alcohol exposure on pregnancy outcome

OBJECTIVE

The aim of this study was to review systematically the available evidence on studies in humans on the effects of low-moderate levels of prenatal alcohol consumption (up to 10.4 UK units or 83 g/week) compared with consumption of no alcohol on pregnancy outcome.

DESIGN

Systematic review.

POPULATION

Pregnant women or women who are trying to become pregnant.

METHODS

The search strategy included Medline, Embase, Cinahl and PsychInfo for the years 1970-2005. Titles and abstracts were read by two researchers and inclusion/exclusion being decided according to prespecified criteria. All the included articles were then obtained and read in full by the two researchers to decide on inclusion. The articles were assessed for quality using the Newcastle-Ottawa Quality Assessment Scales.

MAIN OUTCOME MEASURES

Outcomes considered were miscarriage, stillbirth, intrauterine growth restriction, prematurity, birthweight, small for gestational age at birth and birth defects including fetal alcohol syndrome.

RESULTS

The search resulted in 3630 titles and abstracts, which were narrowed down to 46 relevant articles. At low-moderate levels of consumption, there were no consistently significant effects of alcohol on any of the outcomes considered. Many of the reported studies had methodological weaknesses.

CONCLUSIONS

This systematic review found no convincing evidence of adverse effects of prenatal alcohol exposure at low-moderate levels of exposure. However, weaknesses in the evidence preclude the conclusion that drinking at these levels during pregnancy is safe.

Candida parapsilosis infection in very low birthweight infants

In a UK national surveillance study, we found that Candida parapsilosis accounted for one quarter of all cases of invasive fungal infection in very low birthweight infants. C parapsilosis was associated with fewer deep-seated infections than C albicans, but mortality was similar. Ongoing surveillance is needed to monitor the epidemiology of invasive fungal infection in very low birthweight infants.

Antiretrovirals for reducing the risk of mother-to-child transmission of HIV infection

BACKGROUND

Antiretroviral drugs (ARV) reduce viral replication and can reduce mother-to-child transmission of HIV either by lowing plasma viral load in pregnant women or through post-exposure prophylaxis in their newborns. In rich countries, highly active antiretroviral therapy (HAART) has reduced the vertical transmission rates to around 1-2%, but HAART is not yet widely available in low and middle income countries. In these countries, various simpler and less costly antiretroviral regimens have been offered to pregnant women or to their newborn babies, or to both.

OBJECTIVES

To determine whether, and to what extent, antiretroviral regimens aimed at decreasing the risk of mother-to-child transmission of HIV infection achieve a clinically useful decrease in transmission risk, and what effect these interventions have on maternal and infant mortality and morbidity.

SEARCH STRATEGY

We sought to identify all relevant studies regardless of language or publication status by searching the Cochrane HIV/AIDS Review Group Trials Register, The Cochrane Library, Medline, EMBASE and AIDSearch and relevant conference abstracts. We also contacted research organizations and experts in the field for unpublished and ongoing studies. The original review search strategy was updated in 2006.

SELECTION CRITERIA

Randomised controlled trials of any antiretroviral regimen aimed at decreasing the risk of mother-to-child transmission of HIV infection compared with placebo or no treatment.

DATA COLLECTION AND ANALYSIS

Two authors independently selected relevant studies, extracted data and assessed trial quality. For the primary outcomes, we used survival analysis to estimate the probability of infants being infected with HIV (the observed proportion) at various specific time-points and calculated efficacy at a specific time as the relative reduction in the proportion infected. Efficacy, at a specific time, is defined as the preventive fraction in the exposed group compared to the reference group, which is the relative reduction in the proportion infected: 1-(Re/Rf). For those studies where efficacy and hence confidence intervals were not calculated, we calculated the approximate confidence intervals for the efficacy using recommended methods. For analysis of results that are not based on survival analyses we present the relative risk for each trial outcome based on the number randomised. No meta-analysis was conducted as no trial assessed the identical drug regimens.

MAIN RESULTS

Eighteen trials including 14,398 participants conducted in 16 countries were eligible for inclusion in the review. The first trial began in April 1991 and assessed zidovudine (ZDV) versus placebo and since then, the type, dosage and duration of drugs to be compared has been modified in each subsequent trial. Antiretrovirals versus placebo In breastfeeding populations, three trials found that:ZDV given to mothers from 36 to 38 weeks gestation, during labour and for 7 days after delivery significantly reduced HIV infection at 4-8 weeks (Efficacy 32.00%; 95% CI 0.64 to 63.36), 3 to 4 months (Efficacy 34.00%; 95% CI 6.56 to 61.44), 6 months (Efficacy 35.00%; 95% CI 9.52 to 60.48), 12 months (Efficacy 34.00%; 95% CI 8.52 to 59.48) and 18 months (Efficacy 30.00%; 95% CI 2.56 to 57.44).ZDV given to mothers from 36 weeks gestation and during labour significantly reduced HIV infection at 4 to 8 weeks (Efficacy 44.00%; 95% CI 8.72 to 79.28) and 3 to 4 months (Efficacy 37.00%; 95% CI 3.68 to 70.32) but not at birth.ZDV plus lamivudine (3TC) given to mothers from 36 weeks gestation, during labour and for 7 days after delivery and to babies for the first 7 days of life (PETRA 'regimen A') significantly reduced HIV infection (Efficacy 63.00%; 95% CI 41.44 to 84.56) and a combined endpoint of HIV infection or death (Efficacy 61.00%; 95% CI 41.40 to 80.60) at 4 to 8 weeks but these effects were not sustained at 18 months.ZDV plus 3TC given to mothers from the start of labour until 7 days after delivery and to babies for the first 7 days of life (PETRA 'regimen B') significantly reduced HIV infection (Efficacy 42.00%; 95% CI 12.60 to 71.40) and HIV infection or death at 4 to 8 weeks (Efficacy 36.00%; 95% CI 8.56 to 63.44) but the effects were not sustained at 18 months.ZDV plus 3TC given to mothers during labour only (PETRA 'regimen C') with no treatment to babies did not reduce the risk of HIV infection at either 4 to 8 weeks or 18 months. In non-breastfeeding populations, three trials found that:ZDV given to mothers from 14 to 34 weeks gestation and during labour and to babies for the first 6 weeks of life significantly reduced HIV infection in babies at 18 months (Efficacy 66.00%; 95% CI 34.64 to 97.36).ZDV given to mothers from 36 weeks gestation and during labour with no treatment to babies ('Thai-CDC regimen') significantly reduced HIV infection at 4 to 8 weeks (Efficacy 50.00%; 95% CI 12.76 to 87.24) but not at birthZDV given to mothers from 38 weeks gestation and during labour with no treatment to babies did not influence HIV transmission at 6 months. Longer versus shorter regimens using the same antiretrovirals One trial in a breastfeeding population found that:ZDV given to mothers during labour and to their babies for the first 3 days of life compared with ZDV given to mothers from 36 weeks and during labour (similar to 'Thai-CDC') resulted in HIV infection rates that were not significantly different at birth, 4-8 weeks, 3 to 4 months, 6 months and 12 months. Three trials in non-breastfeeding populations found that:ZDV given to mothers from 28 weeks gestation during labour and to infants for the first 3 days after birth compared with ZDV given to mothers from 35 weeks gestation through labour and to infants from birth to 6 weeks significantly reduced HIV infection rate at 6 months (Efficacy 45.00%; 95% CI 1.88 to 88.12) but compared with the same regimen ZDV given to mothers from 28 weeks gestation through labour and to infants from birth to 6 weeks did not result in a statistically significant difference in HIV infection at 6 months. ZDV given to mothers from 35 weeks gestation during labour and to infants for the first 3 days after birth was considered ineffective for reducing transmission rates and this regimen was discontinued.An antenatal/intrapartum course of ZDV used for a median of 76 days compared with an antenatal/intrapartum ZDV regimen used for a median 28 days with no treatment to babies in either group did not result in HIV infection rates that were significantly different at birth and at 3 to 4 months. In a programme where mothers were routinely receiving ZDV in the third trimester of pregnancy and babies were receiving one week of ZDV therapy, a single dose of nevirapine (NVP) given to mothers in labour and to their babies soon after birth compared with a single dose of NVP given to mothers only resulted in HIV infection rates that were not significantly different at birth and 6 months. However the reduction in risk of HIV infection or death at 6 months was marginally significant (Efficacy 45.00%; 95% CI -4.00 to 94.00). Antiretroviral regimens using different drugs and durations of treatment In breastfeeding populations, three trials found that:A single dose of NVP given to mothers at the onset of labour plus a single dose of NVP given to their babies immediately after birth ('HIVNET 012 regimen') compared with ZDV given to mothers during labour and to their babies for a week after birth resulted in lower HIV infection rates at 4-8 weeks (Efficacy 41.00%; 95% CI 11.60 to 70.40), 3-4 months (Efficacy 39.00%; 95% CI 11.56 to 66.44), 12 months (Efficacy 36.00%; 95% CI 8.56 to 63.44) and 18 months (Efficacy 39.00%; 95% CI 13.52 to 64.48). In addition, the NVP regimen significantly reduced the risk of HIV infection or death at 4-8 weeks (Efficacy 42.00%; 95% CI 14.56 to 69.44), 3 to 4 months (Efficacy 40.00%; 95% CI 14.52 to 65.48), 12 months (Efficacy 32.00%; 95% CI 8.48 to 55.52) and 18 months (Efficacy 33.00%; 95% CI 9.48 to 56.52). The 'HIVNET 012 regimen' plus ZDV given to babies for 1 week after birth compared with the 'HIVNET 012 regimen' alone did not result in a statistically significant difference in HIV infection at 4 to 8 weeks.A single dose of NVP given to babies immediately after birth plus ZDV given to babies for 1 week after birth compared with a single dose of NVP given to babies only significantly reduced the HIV infection rate at 4 to 8 weeks (Efficacy 37.00%; 95% CI 3.68 to 70.32). Five trials in non-breastfeeding populations found that:In a population in which mothers were receiving 'standard' ARV for HIV infection a single dose of NVP given to mothers in labour plus a single dose of NVP given to babies immediately after birth ('HIVNET 012 regimen') compared with placebo did not result in a statistically significant difference in HIV infection rates at birth and at 4 to 8 weeks. The 'Thai CDC regimen' compared with the 'HIVNET 012 regimen' did not result in a significant difference in HIV infection at 4 to 8 weeks.A single dose of NVP given to babies immediately after birth compared to ZDV given to babies for the first 6 weeks of life did not result in a significant difference in HIV infection rates at 4-8 weeks and 3 to 4 months.ZDV plus 3TC given to mothers in labour and for a week after delivery and to their infants for a week after birth (similar to 'PETRA regimen B') compared with NVP given to mothers in labour and immediately after delivery plus a single dose of NVP to their babies immediately after birth (similar to 'HIVNET 012 regimen') did not result in a significant difference in the HIV infection rate at 4 to 8 weeks. (ABSTRACT TRUNCATED)

Antibiotics for treating bacterial vaginosis in pregnancy

BACKGROUND

Bacterial vaginosis is an imbalance of the normal vaginal flora with an overgrowth of anaerobic bacteria and a lack of the normal lactobacillary flora. Bacterial vaginosis during pregnancy has been associated with poor perinatal outcome and, in particular, preterm birth (PTB). Identification and treatment may reduce the risk of PTB and its consequences.

OBJECTIVES

To assess the effects of antibiotic treatment of bacterial vaginosis in pregnancy.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (May 2006).

SELECTION CRITERIA

Randomized trials comparing antibiotic treatment with placebo or no treatment, or comparing two or more antibiotic regimens in pregnant women with bacterial vaginosis or intermediate vaginal flora.

DATA COLLECTION AND ANALYSIS

Two review authors assessed trials and extracted data independently. We contacted study authors for additional information.

MAIN RESULTS

We included fifteen trials of good quality, involving 5888 women. Antibiotic therapy was effective at eradicating bacterial vaginosis during pregnancy (Peto odds ratio (OR) 0.17, 95% confidence interval (CI) 0.15 to 0.20; 10 trials, 4357 women). Treatment did not reduce the risk of PTB before 37 weeks (Peto OR 0.91, 95% CI 0.78 to 1.06; 15 trials, 5888 women), or the risk of preterm prelabour rupture of membranes (PPROM) (Peto OR 0.88, 95% CI 0.61 to 1.28; four trials, 2579 women). However, treatment before 20 weeks' gestation may reduce the risk of preterm birth less than 37 weeks (Peto OR 0.63, 95% CI 0.48 to 0.84; five trials, 2387 women). In women with a previous PTB, treatment did not affect the risk of subsequent PTB (Peto OR 0.83, 95% CI 0.59 to 1.17, five trials of 622); however, it may decrease the risk of PPROM (Peto OR 0.14, 95% CI 0.05 to 0.38) and low birthweight (Peto OR 0.31, 95% CI 0.13 to 0.75)(two trials, 114 women). In women with abnormal vaginal flora (intermediate flora or bacterial vaginosis) treatment may reduce the risk of PTB before 37 weeks (Peto OR 0.51, 95% CI 0.32 to 0.81; two trials, 894 women). Clindamycin did not reduce the risk of PTB before 37 weeks (Peto OR 0.80, 95% CI 0.60 to 1.05; six trials, 2406 women).

AUTHORS' CONCLUSIONS

Antibiotic treatment can eradicate bacterial vaginosis in pregnancy. This review provides little evidence that screening and treating all pregnant women with asymptomatic bacterial vaginosis will prevent PTB and its consequences. However, there is some suggestion that treatment before 20 weeks' gestation may reduce the risk of PTB. This needs to be further verified by future trials.

Caesarean delivery and risk of stillbirth in subsequent pregnancy: a retrospective cohort study in an English population

OBJECTIVE

Two recent studies indicate an increased risk of stillbirth in the pregnancy that follows a pregnancy delivered by caesarean section. In this study, we report an analysis designed to test the hypothesis that delivery by caesarean section is a risk factor for explained or unexplained stillbirth in any subsequent pregnancy. We also report on the proportion of stillbirths in our study population, which may have been attributable to previous delivery by caesarean section.

DESIGN

Retrospective cohort study.

POPULATION

Linked statistical data set of 81 784 singleton deliveries registered in Oxfordshire and West Berkshire between 1968 and 1989.

METHODS

The crude and adjusted hazard ratios for stillbirth in deliveries following a previous delivery by caesarean section, compared with no previous caesarean, were estimated using Cox regression.

MAIN OUTCOME MEASURE

Stillbirth.

RESULTS

The unadjusted hazard ratios for all, explained, and unexplained stillbirths were 1.54 (95% CI 1.04-2.29); 2.13 (1.22-3.72); and 1.19 (0.68-2.09), respectively. After adjustment for maternal age, parity, social class, previous adverse outcome of pregnancy, body mass indexand smoking the hazard ratios were 1.58 (0.95-2.63), 2.08 (1.00-4.31) and 1.24 (0.60-2.56).

CONCLUSIONS

Pregnancies in women following a pregnancy delivered by caesarean section are at an increased risk of stillbirth. In our study, the risk appears to be mainly concentrated in the subgroup of explained stillbirths. However, there are sufficient inconsistencies in the developing literature about stillbirth risk that further research is needed.

Risk factors for hospital admission related to excessive and/or prolonged postpartum vaginal blood loss after the first 24 h following childbirth

A population case-control study was used to determine risk factors for excessive and/or prolonged vaginal bleeding (described collectively as vaginal loss problems) and uterine infection from 24 h to 3 months postpartum. Data were obtained from women whose maternity care took place in one of two health districts in the south of England. The cases were women remaining in or admitted to hospital with excessive or prolonged vaginal blood loss from 24 h to 3 months postpartum. Two controls for each case were identified; these were women whose delivery was the nearest in time and in the same location as the case delivery. Medical and midwifery records were searched retrospectively to cover hospital admissions for vaginal blood loss problems or uterine infection in postpartum women from 1 January 1994 to 31 December 1995. Data were analysed for 243 cases and 486 controls. Univariable analysis identified 28 variables associated with being a case. Using multivariable analysis, nine factors remained in the final model, with a history of secondary postpartum haemorrhage (PPH) being the most strongly predictive (OR [95% confidence interval] 6.0 [2.1, 16.8]). Vaginal bleeding prior to 24 weeks' gestation (OR 3.0 [1.6, 5.9]), third trimester hospital admission (OR 2.0 [1.4, 2.8]), maternal smoking (OR 2.7 [1.8, 3.9]), a prolonged (OR 3.1 [1.2, 7.5]) or incomplete third stage (OR 2.1 [1.0, 4.4]), and primary PPH (OR 4.7 [1.9, 11.6]) for blood loss >500 mL, were predictive of becoming a case. No significant association was identified for parity (OR 1.1 [0.8, 1.5]) or method of delivery, spontaneous (OR 1.0 [0.7, 1.3]), instrumental (OR 1.4 [0.9, 2.2]) or operative (OR 1.2 [0.8, 1.9]). This is a neglected area of women's health after childbirth, and the value of this study is in the identification of potential risk factors for postpartum morbidity related to vaginal blood loss. Where morbidity occurs, early diagnosis, management and treatment are likely to reduce its extent or duration. It is considered that raising awareness about these factors, both among healthcare professionals and women themselves, may play an important part in the recognition and treatment of postpartum morbidity.