Glossary – Women’s & Newborns’
Woman’s and Newborn’s Health Network
______________________________________________________
Model of Maternity Care:
Updated Evidence on Outcomes
And Safety of Planned Home Birth
February 2011
Government of Western Australia, Department of Health
http://www.healthnetworks.health.wa.gov.au/publications/docs/plannedhomebirthsafety.pdf downloaded July 29, 2013
Glossary and Explanation of Statistical Terms
Adverse event – a non-beneficial outcome measured in a study of an intervention that may or may not have been caused by the intervention.
All or none – all or none of a series of people (case series) with the risk factor(s) experience the outcome. For example, no smallpox develops in the absence of the specific virus; and clear proof of the causal link has come from the disappearance of small pox after large scale vaccination. This is a rare situation.
Allocation (or assignment to groups in a study) – the way that subjects are assigned to the different groups in a study (e.g. Drug treatment/placebo; usual treatment/no treatment). This may be by a random method (see randomised controlled trial) or a nonrandom method (see pseudorandomised controlled study).
Anaesthetist – a person who is medically qualified to deliver anaesthetics. Analgesia – the relief of pain without causing unconsciousness. Antenatal – existing or occurring before birth (also prenatal).
Antenatal care – care of women during pregnancy by doctors and midwives in order to predict and detect problems with the mother or the unborn child. Advice is also offered on other matters relevant to pregnancy and birth.
Antenatal clinic – a clinic in a maternity unit where care is provided by midwives, obstetricians and other health professionals.
Antepartum haemorrhage – bleeding from the birth canal in the second half of pregnancy.
Apgar score – system for assessing the physical condition of infants immediately after birth (a maximum of two points awarded for each of five categories: heart- rate, breathing effort, muscle tone, reflexes and colour).
Augmentation of labour – a medical (e.g. Intravenous oxytocin) or surgical (amniotomy) intervention in an attempt to increase the strength of uterine contractions.
Best practice in maternity care – care that provides for the best possible outcomes for women and babies in terms of clinical safety and effectiveness. It recognizes that different women have different risks in relation to pregnancy and childbirth.
Bias – influences on a study that can lead to invalid conclusions about a treatment or intervention. Bias in research can make a treatment look better or worse than it really is. Bias can even make it look as if the treatment works when it actually doesn’t. Bias can occur by chance or as a result of systematic errors in the design and execution of a study. Bias can occur at different stages in the research process, e.g. in the collection, analysis, interpretation, publication or review of research data.
Cardiotocography – the electronic monitoring and recording of the fetal heart rate and uterine activity (CTG).
Care giver – a health professional providing services for a client or patient.
Case-control study – patients with a certain outcome or disease and an appropriate group of controls without the outcome or disease are selected (usually with careful consideration of appropriate choice of controls, matching, etc) and then information is obtained on whether the subjects have been exposed to the factor under investigation.
Case series – a single group of people exposed to the intervention (factor under study). Post-test – only outcomes after the intervention (factor under study) are recorded in the series of people, so no comparisons can be made. Pre-test/post- test – measures on an outcome are taken before and after the intervention is introduced to a series of people and are then compared (also known as a ‘before- and-after study’).
Clinical outcome – an outcome for a study that is defined on the basis of the clinical outcome being studied (e.g. fracture in osteoporosis, peptic ulcer healing and relapse rates).
Clinically important effect (see also statistically significant effect) – an outcome that improves the clinical outlook for the patient. The recommendations made in clinical outlook for the patient. The recommendations made in clinical practice guidelines should be both highly statistically significant and clinically important.
Cochrane collaboration –an international network that aims to prepare, maintain and disseminate high quality systematic reviews based on randomised controlled trials (RCTs) and when RCTs are not available, the best available evidence from other sources. It promotes the use of explicit methods to minimize bias, and rigorous peer review.
Cohort study – an observational study that takes a group (cohort) of patients and follows their progress over time in order to measure outcomes such as disease or mortality rates and make comparisons according to the treatments or interventions that patients received. Thus within the study group, subgroups of patients are identified (from information collected about patients) and these groups are compared with respect to outcome, e.g. comparing mortality between one group that received a specific treatment and one group which did not (or between two groups that received different levels of treatment).
Cohorts can be assembled in the present and followed into the future (a ‘concurrent’ or ‘prospective’ cohort study) or identified from past records and followed forward from that time up to the present (a ‘historical’ or ‘retrospective’ cohort study). Because patients are not randomly allocated to subgroups, these subgroups may be quite different in their characteristics and some adjustment must be made when analyzing the results to ensure that the comparison between groups is as fair as possible.
Comparative study – a study including a comparison or control group.
Confidence interval (CI) – a way of expressing certainty about the findings from a study or group of studies, using statistical techniques. A confidence internal describes a range of possible effects (of a treatment or intervention) that is consistent with the results of a study or group of studies. A wide confidence interval indicates a lack of certainty or precision about the true size of the clinical effect and is seen in studies with too few patients.
Where confidence intervals are narrow they indicate more precise estimates of effects and a larger sample of patients studied. It is usual to interpret a ‘95%’ confidence interval as the range of effects within which we are 95% confident that the true effect lies.
Confounding – the measure of a treatment effect is distorted because of differences in variables between the treatment and control groups that are also related to the outcome. For example, if the treatment (or new intervention) is trialed in younger patients then it may appear to be more effective than the comparator, not because it is better, but because the younger patients had better outcomes.
Continuity of care – care that helps a woman develop a relationship with the same carer, or group of carers, throughout pregnancy, birth and after the birth. All carers share common ways of working and a common philosophy. The aim is to reduce conflicting advice experienced by women and provide the same philosophy of car throughout the period of care. Continuity of care can be provided in different ways and to varying degrees.
Continuous electronic fetal monitoring – the electronic monitoring and recording of the fetal heart rate and uterine activity (CTG).
Control group – a group of patients recruited into a study that receives no treatment, a treatment of known effect, or a placebo (dummy treatment), in order to provide a comparison for a group receiving an experimental treatment, such as a new drug.
Cross-sectional study – the observation of a defined set of people at a single point in time or time period – a snapshot. This type of study contrasts with a longitudinal study, which follows a set of people over a period of time.
Delivery – birth of the baby and the afterbirth. Diabetes – a disorder with high blood sugar levels caused by inappropriate levels
of the hormone insulin.
Effectiveness – the extent to which an intervention produces favourable outcomes under usual or everyday conditions.
Efficacy – the extent to which an intervention produces favourable outcomes under ideally controlled conditions such as in a randomised controlled trial.
Epidural (anaesthetic or analgesia) – a local anaesthetic injected around the spinal sac causing some numbness in the lower part of the body. It relieves labour pains effectively.
Episiotomy – surgical incision into the perineum and vagina to prevent traumatic tearing during childbirth.
Evidence – data about the effectiveness of a new treatment or intervention derived from studies comparing it with an appropriate alternative. Preferably the evidence is derived from a good quality randomised controlled trial, but it may not be.
Evidence based – the process of systematically finding, appraising and using research findings as the basis for clinical decisions.
Evidence based clinical practice – evidence-based clinical practice involves making decisions about the care of individual patients based on the best research evidence available rather than basing decisions on personal opinions or common practice (which may not always be evidence based). Evidence-based clinical practice therefore involves integrating individual clinical expertise and patient preferences with the best available evidence from research.
Exclusion criteria – see Selection criteria.
Experimental study – a research study designed to test whether a treatment or intervention has an effect on the course or outcome of a condition or disease, where the conditions of testing are to some extent under the control of the investigator. Controlled clinical trial and randomised controlled trial are examples of experimental studies.
External validity – is the degree to which the results of a study can be applied to situations other than those under consideration by the study, for example, for routine clinical practice.
Fetal assessment – assessing and monitoring the fetus during pregnancy.
Fetal malpresentation – where the presenting part of the fetus (i.e. the part which is entering the birth canal first) is unusual (e.g. bottom, shoulder, face or brow, instead of the top of the head).
Fetus – the unborn baby. Fetal – of fetus. General Practitioner (GP) – a doctor who works from a local surgery to provide
medical advice and treatment to patients. Gestation (or gestational age) – length of pregnancy
Guidelines – systematically developed statements that assist in decision-making about appropriate health care for specific clinical conditions.
Heterogeneity – or lack of homogeneity. The term is used in meta-analyses and systematic reviews when the results or estimates of effects of treatment from separate studies seem to be very different, in terms of the size of treatment effects, or even to the extent that some indicate beneficial and others suggest adverse treatment effects. Such results may occur as a result of differences between studies in terms of the patient populations, outcome measures, definition of variables or duration of follow up.
High risk – a term used by clinicians to describe women who have a history of problems in a previous pregnancy or have an existing medical condition or have some potential risk of complications that might require speedy or specialist treatment.
Historical controls – data from either a previously published series or previously treated patients at an institution that are used for comparison with a prospectively collected group of patients exposed to the technology or intervention of interest at the same institution.
Home birth – usually a planned event where the woman decides to give birth at home, with care usually provided by a qualified health professional.
Homogeneity – the results of studies included in a systematic review or meta- analysis are similar and there is no evidence of heterogeneity.
Results are usually regarded as homogeneous when differences between studies could reasonably be expected to occur by chance.
Hypertension – blood pressure which is higher than normal, also used for a disease which is characterized by high blood pressure.
Incidence – the number of new events (new cases of a disease) in a defined population, within a specified period of time.
Inclusion criteria – see Selection criteria. Induction of labour – starting labour artificially by using drugs or other methods.
Intention to treat (ITT) – an analysis of a clinical trial where participants are analysed according to the group to which they were initially randomly allocated, regardless of whether or not they dropped out, fully complied with the treatment, or crossed over and received the other treatment. By preserving the original groups one can be more confident that they are comparable.
Intervention – clinical procedure in pregnancy or labour e.g. induction or labour, delivery of the fetus with forceps or by caesarean section.
Intrapartum – during labour. Labour ward – a suite of rooms set aside in a maternity unit for care of women in
labour.
Level of evidence – a hierarchy of study evidence that indicates the degree to which bias has been eliminated in the study design.
Longitudinal study – a study of the same group of people at more than one point in time. (This type of study contrasts with a cross-sectional study, which observes a defined set of people at a single point in time).
Low risk – is a term used by clinicians to describe a woman whose history and condition suggests there is little likelihood of complications.
Maternal – relates to the mother. Maternal and Fetal Medicine specialist (MFM) – Obstetrician who specialises in
the care of women with high risk pregnancy
Meta-analysis – results from a collection of independent studies (investigating the same treatment) are pooled, using statistical techniques to synthesise their findings into a single estimate of a treatment effect. Where studies are not compatible, e.g. because of differences in the study populations or in the outcomes measured, it may be inappropriate or even misleading to statistically pool results in this way. See also Systematic review and Heterogeneity.
Midwife – a person appropriately educated and registered to practice midwifery and who provides care, advice and assistance during pregnancy, labour and birth, and after the baby is born.
Morbidity – being damaged or diseased.
Mortality – number or frequency of deaths.
Multiparous – having carried more than one pregnancy to a viable stage.
Narcotic – an agent that relieves pain; the term is applied especially to the opioids, i.e. natural or synthetic drugs with morphine-like actions
Neonatal – refers to the first 28 days of life. Neonatal sepsis – poisoning by micro-organisms growing in the baby.
Non-randomised experimental trial – the unit of experimentation (e.g. people, a cluster of people) is allocated to either an intervention group or a control group, using a non-random method such as patient or clinician preference/availability) and the outcomes from each group are compared.
Nulliparous – having never given birth to a viable infant.
Observational study – in research about disease or treatments, this refers to a study in which nature is allowed to take its course. Changes or differences in one characteristic (e.g. whether or not people received a specific treatment or intervention) are studied in relation to changes or differences in others(s) (e.g. whether or not they died), without the intervention of the investigator. There is a greater risk of selection bias than in experimental studies.
Obstetrician – a doctor who specialises in the management and care of pregnant women and childbirth. An obstetrician has specialist education, training and experience and is a fellow of the RANZGOG. Obstetricians provide care in secondary, tertiary and private hospitals.
Obstetrics – services relating to the management and care of pregnancy and childbirth, for example antenatal appointments, labour, delivery and care after the baby is born.
Odds ratio (OR) – ratio of the odds of the outcome in the treatment group to the corresponding odds in the control group.
Operative vaginal delivery – delivery of the baby with the help of forceps or ventouse (vacuum extractor).
Paediatrics – a branch of medicine dealing with the development, care and diseases of children.
Parous – having borne at least one viable offspring (usually more than 24 weeks of gestation).
Peer review – review of a study, service or recommendations by those with similar interests and expertise to the people who produced the study findings or recommendations. Peer reviewers can include professional, patient and carer representatives.
Perinatal – refers to the period from 20 weeks of pregnancy to 28 days after birth. Perineum – the area between the vagina and the anus. Postnatal (also postpartum) – pertaining to the four weeks after birth. Postpartum haemorrhage – excess bleeding from the birth canal after birth. Power – see Statistical power.
Precision – a measure of how close the estimate is to the true value. It is defined as the inverse of the variance of a measurement or estimate. It is related to the P– value (the smaller P-value, the greater the precision). (Also called statistical precision).
Preterm labour – labour occurring at less than 37 completed weeks of pregnancy.
Prolonged Preterm Rupture of Membranes or Preterm Prelabour Rupture of Membranes (PPROM) – bag of waters breaks or leaks well in advance of the due date and before the commencement of labour.
Prospective study – a study in which people are entered into the research and then followed up over a period of time with future events recorded as they happen. This contrasts with studies that are retrospective.
Protocols – an adaptation of a clinical guideline or a written statement to meet local conditions and constraints, and which have legal connotations.
P-value – the probability (obtained from a statistical test) that the null hypothesis (that there is no treatment effect) is incorrectly rejected. The P-value obtained from a statistical test corresponds to the probability of claiming that there is a treatment effect when in fact there is no real effect (see also statistically significant effect).
Qualitative research – is used to explore and understand people’s beliefs, experiences, attitudes, behaviour and interactions. It generates non-numerical data, e.g. a patient’s description of their pain rather than a measure of pain.
Quality of evidence (see also strength of evidence) – degree to which bias has been prevented through the design and conduct of research from which evidence is derived.
Quantitative research – research that generates numerical data or data that can be converted into numbers, for example clinical trials.
Randomisation – a process of allocating participants to treatment or control groups within a controlled trial by using a random mechanism, such as coin toss, random number table, or computer-generated random numbers. Study subjects have an equal chance of being allocated to an intervention or control group thus the two groups are comparable.
Randomised controlled trial – a study to test a specific treatment in which people are randomly assigned to two (or more) groups: one (the experimental group) receiving the treatment that is being tested, and the other (the comparison or control group) receiving an alternative treatment, a placebo (dummy treatment) or no treatment. The two groups are followed up to compare differences in outcomes to see how effective the experimental treatment was. (Through randomisation, the groups should be similar in all aspects apart from the treatment they receive during the study).
Relative risk or risk ratio (RR) – ratio of the proportions in the treatment and control groups with the outcome. This expresses the risk of the outcome in the treatment group relative to that in the control group.
RANZCOG – Royal Australian and New Zealand College of Obstetricians and Gynaecologists.
Respiratory distress in the newborn – difficulty in breathing within a few hours of birth.
Retrospective study – deals with the present and past and does not involve studying future events. This contrasts with studies that are prospective.
Sample – a set of individuals or items selected from the study’s target population so that the hypotheses about the population can be tested.
Selection bias – error due to systematic differences in characteristics between those who are selected for study and those who are not. It invalidates conclusions and generalizations that might otherwise be drawn from such studies.
Selection criteria – explicit standards used by guideline development groups to decide which studies should be included and excluded from consideration as potential sources of evidence.
Statistical power – the ability of a study to demonstrate an association or causal relationship between two variables, given that an association exists. For example, 80% power in a clinical trial means that the study has a 80% chance of ending up with a P value of less than 5% in a statistical test (i.e. a statistically significant treatment effect) if there really was an important difference (e.g. 10% versus 5% mortality) between treatments. If the statistical power of a study is low, the study results will be questionable (the study might have been too small to detect any differences). By convention, 80% is an acceptable level of power. See also p value.
Statistically significant effect (see also clinically important effect) – an outcome for which the difference between the intervention and control groups is statistically significant (i.e. the P-value is less than 0.05). A statistically significant effect is not necessarily clinically important.
Stillbirth – a baby born dead after 20 or 22 completed weeks’ gestation.
Strength of evidence – for an intervention effect includes the level (type of studies), quality (how well the studies were designed and performed to eliminate bias) and statistical precision (P-value and confidence interval).
Systematic review – a review in which evidence from scientific studies has been identified, appraised and synthesised in a methodical way according to predetermined criteria. May or may not include a meta-analysis.
Ultrasound – a diagnostic test which is performed by using ultrasonic waves used to examine the interior organs and structures of the mother and fetus.
Uterus – womb. Validity – of measurement: An expression of the degree to which a measurement
measures what it purports to measure; it includes construct and content validity.
Variable – a measurement that can vary within a study, e.g. the age of participants. Variability is present when differences can be seen between different people or within the same person over time, with respect to any characteristic or feature that can be assessed or measured.
Abbreviations
APH – antepartum haemorrhage CI – confidence interval CTG – cardiotocography gm – grams
ITT – Intention to treat
IPPM – Intrapartum-related Perinatal Mortality
LBW – low birth weight
MFM – Maternal and Fetal Medicine specialist
N or n – Number of participants in a study sample
NHMRC – National Health and Medical Research Council
NICU – Neonatal Intensive Care Unit
OR – Odds Ratio
PE – pre-eclampsia
PPH – postpartum haemorrhage
PPROM – Prolonged Preterm Rupture of Membranes or Preterm Prelabour Rupture of Membranes
RCT – Randomised controlled trial RR – Relative risk
vs – versus as in comparison of proportion of women with a defined characteristic (a% vs b%)
