Maternity initial assessment indicators by mother’s age

Main information

Designation: Accredited official statistics
Data provider: Digital Health and Care Wales (DHCW)
Data source: Maternity Indicators Dataset (MIDS)
Time period covered: January 2016 to December 2025
Dataset ID: b28de382-19a0-47a3-b3c6-b34311284e49

Overview

Summary of dataset and variables

Information recorded at initial assessment on Body Mass Index (BMI), whether the mother reported a mental health condition and whether the initial assessment took place within 10 completed weeks of gestation broken down by mother’s age.

This data is derived from the Maternity Indicators dataset, provided to the Welsh Government by Digital Health and Care Wales (DHCW).

The Maternity Indicators dataset combines records from a mother’s initial assessment with a child’s birth record. Full details of every data item available in the Maternity Indicators dataset are available through the NHS Wales Data Dictionary

Gestational age is estimated from when pregnancy started, based on either date of last menstrual period or from an ultrasound scan.

The mental health conditions listed on the record are categorised as:

puerperal psychosis (severe postnatal depression)
bi-polar effective disorder/manic depression
psychosis
psychotic depression
schizophrenia
and other (any other mental health condition)

Data collection or calculation

Data from the Maternity Indicators dataset only includes initial assessment data where the initial assessment and birth both occurred in the same health board, in Wales only.

Births to Welsh resident mothers who gave birth in England or in any other country outside of Wales are not included in the data.

Data for each calendar year refers to when the baby was born. Initial assessments may have taken place in the previous year but would be counted in the year in which the birth occurred.

Some women may have had their first initial assessment before the date that has been recorded. The merging methodology for the initial assessment and birth record is based on when these occur in the same health board.

It is possible that a mother could have an initial assessment in one health board, early in the pregnancy, but then if she gives birth in another health board she will have another initial assessment recorded at the second health board where she gives birth. A small proportion of initial assessments (1%) were recorded between 39 and 40 weeks.

The percentages are calculated using a denominator of all records minus “not stated”. For gestational age, ‘Not stated’ also includes records where the gestation was stated as 0 weeks.

Records where BMI, height or weight are unrealistic values are classed as invalid, for example where BMI is less than 10 or greater than 100; where the pregnant woman’s weight is less than 30kg or more than 250kg; and where the pregnant woman’s height was less than 120cm or greater than 200cm. The calculation also only includes women who had their initial assessment at 14 completed weeks of pregnancy or earlier. This is to reduce unfair comparisons where the BMI calculation is affected by baby growth where the initial assessment happened after 15 weeks. Between 11% to 15% of all pregnancies have been excluded for this reason in each year.

The number of records excluded can be found in Table 4 of the Maternity and birth statistics quality report tables.

Statistical quality

For BMI, More than 90% of records had valid data for both height and weight data items, across all health boards, in most years apart from: Cwm Taf in 2016 (77%) and in 2019 (88%); and Betsi Cadwaladr in 2019 (89%).

In 2024, Aneurin Bevan has been excluded from analysis due to high levels of invalid data for height leading to 77% missing data for BMI.

For mental health condition at initial assessment, Betsi Cadwaladr have been excluded for the years 2016 to 2023 because of their low reliability. Data from Cwm Taf/Cwm Taf Morgannwg had been excluded from mental health analysis due to data quality concerns prior to 2022. These data quality issues were resolved and data for Cwm Taf/Cwm Taf Morgannwg from 2022 onwards is no longer excluded. While 99% of records had valid data entered in both health boards, the large majority were recorded as having no mental health condition which is unlikely to reflect the actual position in these health boards.

All other health boards have valid data for the mental health data item in at least 88% of records in each year, apart from Cardiff and Vale in 2016 (56% completeness). In 2024, Aneurin Bevan have been excluded due to high levels of missing data (76%).

More detailed information on the sources of data and analyses in this statistical release are provided in the quality report.

Related reports

Published by

Organisation: Welsh Government
Contact email: stats.healthinfo@gov.wales

Maternity initial assessment indicators by mother’s age

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