Publication, Part of Statistics on Women's Smoking Status at Time of Delivery: England
Statistics on Women's Smoking Status at Time of Delivery: England, Quarter 2, 2024-25
Official statistics
Inclusion of new comparative data from the Maternity Services Dataset (MSDS)
For 2024-25, comparative data using the Maternity Services Dataset (MSDS) is also presented using data submitted by Trusts. This is to help support decisions around the retirement of the Smoking at Time of Delivery data collection at the end of 2024-25.
19 September 2024 00:00 AM
Appendices
Appendix A - Definitions
SATOD v1
The Smoking at time of delivery (SATOD) data collection is a Sub Integrated Care Board Location (Sub-ICB) based collection. A mother will be assigned to a Sub-ICB based on the postcode of their GP. This is because a large hospital might serve several Sub-ICBs and also allows for home births to be allocated to a Sub-ICB.
The following data items are submitted for each quarter:
Number of maternities - defined as the number of pregnant women who give birth (during the quarter) to one or more live or stillborn babies of at least 24 weeks gestation, where the baby is delivered by either a midwife or doctor at home or in an NHS hospital (including GP units). This count should be the number of pregnant women (deliveries), rather than the number of babies (babies), i.e., twins are counted as one maternity. It does not include maternities that occur in psychiatric hospitals or private beds / hospitals.
Women known to be smokers at the time of delivery - defined as pregnant women who self-reported that they were smokers. This includes any cigarettes or tobacco at all, but excludes non-combustible nicotine products, such as e-cigarettes or other nicotine containing products. If a woman intends to give up smoking after the delivery but was a smoker up until the delivery date, they are included in this count.
Women known to be non-smokers at the time of delivery - defined as pregnant women who self-reported that they were non-smokers (no cigarettes or tobacco at all). This count does not include women whose smoking status is not known (which is collected separately), or those who intend to give up smoking after delivery.
Women whose smoking status was not known at the time of delivery - defined as those whose smoking status was not determined for whatever reason.
Geographical breakdowns
All breakdowns are based on the GP Practice code of the mother except Local Authority (LA) breakdowns which are based on the home postcode of the mother.
SATOD v2
The Maternity Services Data Set (MSDS) is a patient-level data set that captures information about activity carried out by NHS Maternity Services relating to a mother and baby(s), from the point of the first booking appointment until mother and baby(s) are discharged from maternity services. As a secondary uses data set, MSDS re-uses clinical and operational data for purposes other than direct patient care. It defines the data items, definitions and associated value sets extracted or derived from local information systems and sent to NHS England for analysis purposes. The information is submitted by Trusts on a monthly basis so three months worth of data have been combined to generate numbers to compare with SATOD v1.
The following data items have been derived for each quarter:
Number of maternities - Defined as the number of pregnant women who give birth (during the quarter) to one or more live or stillborn babies of at least 24 weeks gestation, where the baby is delivered by either a midwife or doctor at home or in an NHS hospital (including GP units). This count is the number of pregnant women (deliveries), rather than the number of babies (births), i.e., twins are counted as one maternity. It does not include maternities that occur in psychiatric hospitals or private beds / hospitals.
Women known to be smokers at the time of delivery - Defined as the number of pregnant women who were current smokers +/-3 days from the labour onset date. Smoking status is identified via clinical coding in MSDS (see table below).
Women known to be non-smokers at the time of delivery - Defined as the number of pregnant women who were non-smokers +/-3 days from the labour onset date. Smoking status is identified via clinical coding in MSDS (see table below).
Women whose smoking status was not known at the time of delivery - Defined as the number of pregnant women who were unable to be assigned a consistent smoking status within +/-3 days from the labour onset date. This is because either no status could be assigned, or there were conflicting statuses within the birth period e.g. both smoker and non-smoker recorded.
Geographical breakdowns
All MSDS data is submitted by Trusts. The Sub-ICB breakdown is based on the GP Practice code of the mother submitted in MSDS and Local Authority (LA) breakdowns are based on the home postcode of the mother submitted in MSDS.
Clinical codes to submit to MSDS
This is the short list of SNOMED codes used to identify smoking status from MSDS, listing the relevant codes for the two categories of smoker and non-smoker. This is the preferred list of SNOMED codes relating to smoking status to be submitted to MSDS.
Group |
SNOMED code |
Description |
Current smoker |
77176002 |
Smoker (finding) |
Non-smoker |
266919005 |
Never smoked tobacco (finding) |
8517006 |
Ex-smoker (finding) |
|
8392000 |
Non-smoker (finding) |
|
405746006 |
Current non smoker but past smoking history unknown (finding) |
Below is the long list of other SNOMED codes which can be used to identify smoking status from MSDS. These codes will still be accepted in relation to smoking status, but those included in the above short list are the preferred ones to use.
Non-smoker / ex-smoker
SNOMED code | Description |
105539002 | Non-smoker for personal reasons (finding) |
105540000 | Non-smoker for religious reasons (finding) |
105541001 | Non-smoker for medical reasons (finding) |
53896009 | Tolerant ex-smoker (finding) |
87739003 | Tolerant non-smoker (finding) |
160618006 | Current non-smoker (finding) |
266921000 | Ex-trivial cigarette smoker (<1/day) (finding) |
266922007 | Ex-light cigarette smoker (1-9/day) (finding) |
266923002 | Ex-moderate cigarette smoker (10-19/day) (finding) |
266924008 | Ex-heavy cigarette smoker (20-39/day) (finding) |
266925009 | Ex-very heavy cigarette smoker (40+/day) (finding) |
266928006 | Ex-cigarette smoker amount unknown (finding) |
281018007 | Ex-cigarette smoker (finding) |
360890004 | Intolerant ex-smoker (finding) |
360900008 | Aggressive ex-smoker (finding) |
360918006 | Aggressive non-smoker (finding) |
360929005 | Intolerant non-smoker (finding) |
492191000000103 | Ex roll-up cigarette smoker (finding) |
1092031000000108 | Ex-smoker amount unknown (finding) |
1092041000000104 | Ex-very heavy smoker (40+/day) (finding) |
1092071000000105 | Ex-heavy smoker (20-39/day) (finding) |
1092091000000109 | Ex-moderate smoker (10-19/day) (finding) |
1092111000000104 | Ex-light smoker (1-9/day) (finding) |
1092131000000107 | Ex-trivial smoker (<1/day) (finding) |
48031000119106 | Ex-smoker for more than 1 year (finding) |
160620009 | Ex-pipe smoker (finding) |
160621008 | Ex-cigar smoker (finding) |
160618006 | Current non-smoker (finding) |
Current smoker
SNOMED code | Description |
56578002 | Moderate smoker (20 or less per day) (finding) |
56771006 | Heavy smoker (over 20 per day) (finding) |
59978006 | Cigar smoker (finding) |
65568007 | Cigarette smoker (finding) |
82302008 | Pipe smoker (finding) |
160603005 | Light cigarette smoker (1-9 cigs/day) (finding) |
160604004 | Moderate cigarette smoker (10-19 cigs/day) (finding) |
160605003 | Heavy cigarette smoker (20-39 cigs/day) (finding) |
160606002 | Very heavy cigarette smoker (40+ cigs/day) (finding) |
160616005 | Trying to give up smoking (finding) |
160619003 | Rolls own cigarettes (finding) |
230059006 | Occasional cigarette smoker (finding) |
230060001 | Light cigarette smoker (finding) |
230062009 | Moderate cigarette smoker (finding) |
230063004 | Heavy cigarette smoker (finding) |
230064005 | Very heavy cigarette smoker (finding) |
230065006 | Chain smoker (finding) |
266920004 | Trivial cigarette smoker (less than one cigarette/day) (finding) |
266929003 | Smoking started (finding) |
308438006 | Smoking restarted (finding) |
365981007 | Finding of tobacco smoking behaviour (finding) |
365982000 | Finding of tobacco smoking consumption (finding) |
394871007 | Thinking about stopping smoking (finding) |
394873005 | Not interested in stopping smoking (finding) |
446172000 | Failed attempt to stop smoking (finding) |
203191000000107 | Wants to stop smoking (finding) |
428041000124106 | Occasional tobacco smoker (finding) |
Appendix B – Validations
SATOD v1
The following validation is undertaken by the NHS England data collections system on each quarter’s submission:
Number of women known to be smokers at the time of delivery +
Number of women known to be non-smokers at the time of delivery +
Number of women whose smoking status was not known at the time of delivery = Number of maternities
A submission that fails this validation is not accepted. In this situation the Sub-ICB is prompted to amend and re-submit their data until their submission passes this validation.
Further validations are then undertaken to check if:
- the number of maternities is +/-15% of an average of the previous 4 quarters;
- the number of women known to be smokers at the time of delivery is +/-15% of an average of the previous 4 quarters;
- the number of women known to be non-smokers at the time of delivery is +/-15% of an average of the previous 4 quarters;
- the number of women whose smoking status was not known is above or equal to 5% of number of maternities
If any of the above are true then the Sub-ICB is able to amend the data and re-submit, or must either confirm if it is affected by data quality issues, or confirm the data as correct. Where data quality issues are identified, further explanation must be provided which is included within the published data tables (DQ Table 1).
SATOD v2
Standard validation is undertaken by NHS England data collections system for each Trust’s monthly MSDS submission. This includes ensuring mandatory data tables and data fields are included in the submission. More information is available on our website about Understanding data quality in the SDCS Cloud submission tool and Implementing the Maternity Services Data Set (MSDS) v2.0 tools and guidance including the Technical Output Specification (TOS) which sets out which data tables and fields are mandatory.
NHS England further validates the MSDS data used for this metric against a set of data quality checks, which were put in place for the Smoking at Delivery CQIM metric that forms the basis for SATOD v2.
There are three CQIM data quality metrics used for this validation: CQIMDQ02, CQIMDQ06, CQIMDQ07. They are applied to each Trust’s submission of each of the three month’s data that makes up a quarter of MSDS data used for SATOD v2 metric.
A Trust’s data submission which fails any of those three checks for even one month’s data in the relevant quarter, is then not included in the calculation of that quarter’s SATOD v2 figures. This helps explain why the number of maternities reported in SATOD v2 are lower than the number of maternities reported in SATOD v1.
A full description of each data quality metric, including their construction and their pass rates, is available in the Metadata file accompanying the Maternity Services Monthly Statistics publication series.
Appendix C – Methodology
SATOD v1
Percentage of women known to be smokers at time of delivery
This measure is calculated as:
Number of women known to be smokers at the time of delivery / (Number of maternities - Number of women whose smoking status was not known at the time of delivery) * 100
Prior to April 2017, this calculation included women with an unknown smoking status in the denominator i.e. the total number of maternities. This meant that women with an unknown smoking status were being treated in the same way as non-smokers. Thus poor data quality (i.e. having a lot of unknowns) would cause a false under-representation of this metric. The tables in this report showing a time series have been recalculated to use the current new definition. More information is available in the methodological change note.
The methodology used in the Public Health Outcomes Framework (PHOF) indicator has also changed to exclude those maternities with an unknown status from the denominator. More information is available in the Government response to the consultation on the Public Health Outcomes Framework (PHOF).
SATOD v2
Percentage of women known to be smokers at time of delivery
This measure is calculated the same as SATOD v1:
Number of women known to be smokers at the time of delivery / (Number of maternities - Number of women whose smoking status was not known at the time of delivery) * 100
We have used smoking statuses recorded in Table MSD302 Care Activity (Labour and Delivery) and Table MSD202 (Care Activity Pregnancy), giving priority to smoking statuses recorded in Table MSD302 Care Activity (Labour and Delivery) when there are duplicate records in the +/-3 days from the labour onset date, as MSD302 records are more likely to be associated with Smoking at Time of Delivery.
Confidence intervals
A confidence interval gives an indication of the likely error around an estimate that has been calculated from measurements based on a sample of the population. It indicates the range within which the true value for the population as a whole can be expected to lie, taking natural random variation into account.
Throughout this report, 95% confidence intervals are used. These are known as such because if it were possible to repeat the same programme under the same conditions a number of times, we would expect 95% of the confidence intervals calculated in this way to contain the true population value for that estimate.
This approach is consistent with that used throughout the public health community.
The significance of the difference between two rates or proportions has been carried out throughout this report using the method described by Wilson and Newcombe below:
1. Calculate the proportions of women with and without the feature of interest (e.g. percentage of maternities who smoke at the time of delivery).
r = recorded number of maternities that smoke at the time of delivery for the designated time period
n = sample size
p = ( r / n ) proportion with feature of interest
q = ( 1 - p ) proportion without feature of interest
z = appropriate value z1-a/2 from the standard Normal distribution (1.96 for the 95% confidence interval).
2. Calculate three values (A, B and C) as follows:
\(A = 2r + z^2\)
\(B = z \sqrt{z^2+4rq}\)
\(C = 2(n+z^2)\)
3. Then the confidence interval for the population proportion is given by
\({A-B \over C}\) to \({A+B \over C}\)
This method has advantages to other approaches as it can be used for any data.
When there are no observed events, then r and hence p are both zero, and the recommended confidence interval simplifies to 0 to \({z^2 \over n+z^2}\) . When r = n so that p = 1, the interval becomes \({n \over n+z^2}\) to 1.
Appendix D: How are the statistics used?
Users and uses of the report
Below is listed our current understanding of the known users and uses of these statistics.
Reducing smoking during pregnancy was one of the three national ambitions in the Tobacco Control Plan published back in July 2017. A new Tobacco and Vapes Bill was introduced in 2024 and it is anticipated that new strategies around reducing smoking in pregnancy are being developed under the new government. The DHSC publishes policies on smoking.
The reports are also available to support responses to parliamentary questions.
The Office for Health Improvement and Disparities (OHID) - frequently use these data for secondary analysis and convert the Sub-ICB (formerly CCG) level data to local authority level and use it within the Public Health Outcomes Framework as indicator 2.03. They also use these data within the Local Tobacco Control Profiles.
Media - these data are used to underpin articles in newspapers, journals, etc.
Public - all information is accessible for general public use for any particular purpose.
NHS - Use the reports and tables for analyses, benchmarking and to inform decision making.
Public Health Campaign Groups - data are used to inform policy and decision making and to examine trends and behaviours.
Unknown Users
This publication is free to access via the NHS England website and consequently the majority of users will access the report without being known to us. Therefore, it is important to put mechanisms in place to try to understand how these additional users are using the statistics and also to gain feedback on how we can make these data more useful to them. On the webpage where the publication appears there is a “Contact us” link at the bottom of the page. Any responses are passed to the team responsible for the report to consider.
Last edited: 19 December 2024 9:31 am