NHS Maternity Statistics

Birth vs Delivery Definitions A delivery episode relates to the mother. It is the episode in which she delivers her baby/ babies. There is only one delivery episode regardless of whether the mother delivers one baby (a singleton) or more than one (i.e. twins, triplets etc). Delivery episodes are counted using a filter on the episode type field (2 & 5) and FCEs. A birth episode relates to the baby. It is the baby’s first episode, i.e. when they are born. Each baby has its own birth episode so the count of birth episodes will always be higher than delivery episodes, as each baby from a multiple birth will have its own birth episode. Birth episodes are counted using a filter on the episode type field (3 & 6) and FCEs.

Data quality issue Sextuplets: 2006/07 universe only There are large numbers (47,000) of delivery records containing spurious tails. Instead of the one or two tails that should be attached to the delivery record, typically 6 delivery tails are present. Birth records are not affected. Impact – large numbers of delivery records representing high order multiple births are present in the data. Caution is advised when using any of the secondary tails.

Which count to use and why? Birth and delivery episodes should not be counted together as they both correspond to the same event - a woman giving birth. The HES team tend to count delivery episodes as most of our analysis is around the process of delivering the baby. Publication tables only include data for the first baby born in a multiple birth (i.e. fields from the first tail); the vast majority of babies are singletons so this method only excludes a small proportion of babies- and it also avoids counting the duplicate records described above.

Business Objects Delivery 1, Delivery 2 and Birth Business Objects contains 3 classes containing maternity data: “Delivery 1”, “Delivery 2” and “Birth”. Both Delivery 1 and Delivery 2 contain exactly the same fields, all of which relate to the mother, e.g. how long she was in hospital and the type of anaesthetic she had during labour. Delivery 1 has one “tail” which has an additional set of fields relating to the baby/babies such as their weight and whether they were live or still born. The information within the tail of delivery 1 covers all babies, not just the first baby or singletons. Mum A has twins, the information about her delivery would be copied against two separate records- one for each baby. The structure of the records are as follows; Mum A: Baby 1 Mum A: Baby 2 …1 row per baby with duplicate delivery information for multiple births

Business Objects Delivery 1, Delivery 2 and Birth Delivery 2 has 9 tails; each baby from a multiple birth would have information recorded in its own tail, so there is space to record details for up to 9 babies! (See data quality note above regarding baby tails). In delivery 2 the data is structured as one row per delivery therefore “Mum A” would only have one set of delivery details, followed by the details about each of her babies: Mum A: Baby 1, Baby 2…. If you selected birth order=1 using delivery 1 you should technically get the same results as using delivery 2 and tail 1.

Business Objects Delivery 1, Delivery 2 and Birth The Birth class contains exactly the same fields as delivery 1 and 2 and has one record per birth (baby) these fields should be used when looking at birth episodes. ONS are the official source of registered births data so where ever possible the HES team refer customers/ PQ’s asking about births to ONS in order to avoid having different birth counts in the public domain. HES does contain certain clinical information which is not captured by ONS, when this information is requested we would use HES birth episodes. The separation of delivery 1, delivery 2 and birth classes often confuses users as each class seems to contain the same fields in a slightly different order or arrangement. The HES data quality team will be changing the structure of the maternity fields within Business Objects in the near future.

Business Objects

Creating a Business Objects query Conditions The following conditions are applied to all maternity queries: 1.Episode type in list 2 & 5 (see rationale above regarding which episode type to use) 2.Delivery place type (actual) NOT IN LIST : 1, 5 & 6. This ensures we are only counting deliveries taking place in an NHS hospital. As HES only covers approximately 13% of NHS home births, it would be misleading to include these in our reports. Coverage for NHS births in the independent sector is similarly low. Obviously it is possible to add other conditions, but those listed above should be included as a general rule.

Creating a Business Objects query

Delivery method OPCS vs delivery method field It is possible to identify the method of delivery (how the baby was born) using the HES “delivery method” (delmeth) field from the maternity tail or, alternatively, from equivalent operation (OPCS) codes. OPCS codes offer a much more robust measure of method of delivery because of the link to Payment by Results (PbR). 95% of delivery episodes have an OPCS code recorded for the method of delivery (main procedure) compared to 72% of delivery episodes using the “method of delivery” field.

Delivery method comparison DescriptionOPCS codeHES Delivery Method Field Total Delivery Episodes629,207 Unknown Delivery Method31,176174,782 Spontaneous Vertex379,629277,709 Spontaneous Other2,15915,075 Forceps Low12,99710,789 Forceps Other13,5159,721 Ventouse42,01230,258 Breech2,3012,292 Breech Extraction Caesarean Elective56,99741,921 Caesarean Emergency88,05461,070 Other Delivery Method965,189 High number of unknown delivery method using maternity tail

Business Objects

Understanding the output Data Quality Due to poor data quality and coverage, many of the maternity fields have high numbers of “unknowns”. As well as this “impossible/ unlikely” events are often created when fields are cross tabulated. These include events such as post natal stay of one day occurring when the delivery method was a caesarean section or general anaesthetic given for a spontaneous delivery. Such events have been highlighted in the publication tables in order to alert users of the poor data quality

Data quality Footnote Data Quality This extract/ tabulation includes impossible or very unlikely events such as spontaneous deliveries with a general anaesthetic; spontaneous deliveries after Caesarean onset and unrealistic data in relation to gestation length and birth weight. No attempt has been made to correct the data as it is impossible to be sure which part of the data is incorrect i.e. whether or not the delivery was spontaneous or whether or not a general anaesthetic had been used. Please treat with caution.

Data quality example

Other issues Well babies Recent investigations have found data quality issues with the “Well babies” flag. Therefore at this time we recommend that this is not used to identify well babies. As an interim measure we advise using a count of birth episodes where the primary diagnosis is Z38 to count well babies. Further investigation is underway into this and it is intended that the underlying issues will be resolved in the near future. Normal deliveries The figures for normal deliveries in have been removed from Table 33 as there was an error in the calculation. Because of the complexity of both the definition and the calculation of these figures the NHS Information Centre intends to consult expert users and clinicians in order to ensure that the definition of a "normal" delivery and the method used to extract the data from the Hospital Episode Statistics database are both clinically and statistically relevant, and reflect current best practice. The implications of any changes will also be investigated for figures published prior to Other figures are not affected.

Finally… Website D=1937&categoryID=1009 Contact Victoria May Kathryn Garnett Tom Woodhead