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Publication, Part of

Statistics on Women's Smoking Status at Time of Delivery: England, Quarter 2, 2021-22

Official statistics

Data quality statement

Purpose of document

This data quality statement aims to provide users with an evidence based assessment of quality of the statistical output included in this publication. 

It reports against those of the nine European Statistical System (ESS) quality dimensions and principles appropriate to this output. The original quality dimensions are: relevance, accuracy and reliability, timeliness and punctuality, accessibility and clarity, and coherence and comparability; these are set out in Eurostat Statistical Law. However more recent quality guidance from Eurostat includes some additional quality principles on: output quality trade-offs, user needs and perceptions, performance cost and respondent burden, and confidentiality, transparency and security.


In doing so, this meets NHS Digital’s obligation to comply with the UK Statistics Authority (UKSA) code of practice for statistics and the following principles in particular:

  • Trustworthiness pillar, principle 6 (Data governance) which states “Organisations should look after people’s information securely and manage data in ways that are consistent with relevant legislation and serve the public good.”
  • Quality pillar, principle 3 (Assured Quality) which states “Producers of statistics and data should explain clearly how they assure themselves that statistics and data are accurate, reliable, coherent and timely.”
  • Value pillar, principle 1 (Relevance to Users) which states “Users of statistics and data should be at the centre of statistical production; their needs should be understood, their views sought and acted upon, and their use of statistics supported.”
  • Value pillar, principle 2 (Accessibility) which states “Statistics and data should be equally available to all, not given to some people before others. They should be published at a sufficient level of detail and remain publicly available.”


This dimension covers the degree to which the statistical product meets user needs in both coverage and content.

This report is used to measure progress against one of the three national ambitions in the Tobacco Control Plan 2017, which was “to reduce rates of smoking throughout pregnancy to 6 per cent or less by the end of 2023 (measured at time of giving birth)”.

It is also used to populate indicator 2.3 in the Public Health Outcomes Framework (PHOF) and indicator 1.14 in the CCG Outcome Indicator Set (CCGOIS)

The report covers data provided by all Clinical Commissioning Groups (CCGs) in England.


Accuracy and reliability

This dimension covers, with respect to the statistics, their proximity between an estimate and the unknown true value.

In Quarter 4, revised data is accepted from CCG’s for quarters 1, 2, and 3. The reports for Quarters 1,2 and 3 are therefore published on a provisional basis, with the final report being produced in Quarter 4.

Validation takes place at the point of entry. Further details on the validations carried out can be found in section B of the appendices

DQ Table 1 of the Excel data tables contains data quality indicators for the latest quarter showing the percentage of women where the smoking status is not known, as well as the percentage difference compared to the average of the previous four quarters for:

  • Maternities
  • Women known to be smokers at time of delivery
  • Women known to be non-smokers at time of delivery

In order to highlight any areas of concern and to encourage improvements, a CCG must provide a reason when they breach one of the validation checks. Where a data quality issue was identified, the reason provided is included in the table.

The smoking status is self-reported by the woman and therefore may be susceptible to “satisficing” where the woman is tempted to give an answer which is more socially acceptable, i.e. to say she is a non-smoker. Also, the definition does not distinguish between heavy and light smokers or how recently the woman smoked.


Timeliness and punctuality

Timeliness refers to the time gap between publication and the reference period. Punctuality refers to the gap between planned and actual publication dates.

Publication occurs around 8 to 10 weeks after the end of the reporting period. The publication has not suffered any delay to the pre-announced release date.


Accessibility and clarity

Accessibility is the ease with which users are able to access the data, also reflecting the format in which the data are available and the availability of supporting information. Clarity refers to the quality and sufficiency of the metadata, illustrations and accompanying advice.

All reports are accessible on the NHS Digital website. Data tables are provided in Excel format and as csv files, as part of the government’s requirement to make public data public.

NHS Digital has produced these reports since Quarter 3 2011-12.  Prior to this the Department of Health and Social Care (DHSC) produced these reports, which are available at the links below:

DHSC Smoking at delivery 2009-10 to 2011-12

DHSC Smoking at delivery 2005-06 to 2009-10


Coherence and comparability

Coherence is the degree to which data which have been derived from different sources or methods but refer to the same topic are similar. Comparability is the degree to which data can be compared over time and domain. 

The data in this report supplements the Adult Smoking Habits in the UK report which provides information on smoking rates, average number of cigarettes smoked and smoking during pregnancy at a national level. This continues the series of releases on smoking; previously provided by the General Household Survey (GHS) and the General Lifestyle Survey (GLF).

On 1 April 2013, responsibility for commissioning services for women’s smoking status at the time of delivery moved from Primary Care Trusts (PCTs) to CCGs. 

Changes to CCG and regional structure from 1st April 2021

On 1 April 2021, 38 CCGs are merged to create 9 new CCGs. Full details can be found at the link below:

April 2021 CCG organisational re-structure


Change in definition for calculating the proportion of women smoking at time of delivery

From April 2017, the methodology used to calculate the proportion of women smoking at the time of delivery changed to exclude women with an unknown smoking status from the denominator. Previously the percentage of unknowns may have resulted in the under reporting of the percentages for known smokers and non-smokers as they were effectively treated as non-smokers in the calculation. Information on these changes can be found in section C of the appendices. National time series data in table 1 was updated for all years to reflect the new methodology and is therefore comparable.



Trade-offs between output quality components

This dimension describes the extent to which different aspects of quality are balanced against each other. 

The smoking status is self-reported by the woman and therefore may be susceptible to “satisficing” where the woman is tempted to give an answer which is more socially acceptable, i.e. to say she is a non-smoker.

Additionally, the definition does not distinguish between heavy and light smokers, or how recently the woman smoked.


Assessment of user needs and perceptions

This dimension covers the processes for finding out about users and uses and their views on the statistical products. 

This publication is considered to be of particular interest to English NHS commissioning organisations. However, data and findings are also likely to be of interest to a broader base of users.

A consultation took place in 2016 across all NHS Digital statistical outputs which included this report.  The results of the consultation are published here.

NHS Digital is keen to gain a better understanding of the users of this publication and of their needs; feedback is welcome and may be sent to (please include ‘Smoking Status at Time of Delivery’ in the subject line).


Performance, cost and respondent burden

This dimension describes the effectiveness, efficiency and economy of the statistical output.

The cost incurred by data providers to collect and submit the Smoking at Time of Delivery Data was last estimated in 2013 at £148,000.  The cost of collecting, processing and publishing the data centrally is estimated to be £35,000 per annum.


Confidentiality, transparency and security

The procedures and policy used to ensure sound confidentiality, security and transparent practices. 

These publications are subject to a NHS Digital risk assessment prior to issue.

Information is disseminated at a high level of aggregation and the only small numbers that occur do not require suppressing as they are not considered identifiable or disclosive.

The data contained in this publication are National Statistics. The code of practice for statistics is adhered to from collecting the data to publishing.

Details of relevant procedure and policy information can be found below:

NHS Digital Statistical Governance Policy

NHS Digital Freedom of Information Process

NHS Digital Statement of Compliance with Pre-Release Order

NHS Digital Disclosure Control Procedure

Last edited: 13 December 2021 10:02 am