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Fabiola-Eto / MULTIPLY-Initiative

This repository hosts codelists of long-term conditions addressed in a multimorbidity study developed by researchers from the Queen Mary University of London, Welcome Trust Sanger Institute and the London School of Hygiene and Tropical Medicine.
MIT License
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CPRD pregnancy register - operationalising or this analysis #196

Closed Miriam-S-git closed 1 year ago

Miriam-S-git commented 2 years ago

Hi,

The CPRD pregnancy register identifies lots of data for the pregnancies. The methodology is here.

https://onlinelibrary.wiley.com/doi/full/10.1002/pds.4811#support-information-section

For our purpose we are interested in Pregnancies to the third trimester: Still birth/Live Birth.

1) Assessing pregnancies that reached the third trimester - we need the following variable. 'pregstart' - estimated start date of pregnancy 'pregend' - estimated end date of pregnancy 'Thirdtrim3' - estimated start date of third trimester ( We can calculate whether pregnancies made it to the 3rd trimester using these dates).

2) Assessing the pregnancy outcomes - live birth or still birth. - we need the following variable: 'outcome'

Interpreting the outcome codes: 1 = Live birth, 2 = Stillbirth,

The following would be classes as pregnancy loss/still birth (if present); 3 = 1 and 2, 4 = Miscarriage, 5 = TOP, 6 = 4 or 5, 7 = Ectopic, 8 = Molar, 9 = Blighted ovum, 10 = Unspecified loss,

The following suggest outcome unknown: 11 = Delivery based on a third trimester pregnancy record, 12 = Delivery based on a late pregnancy record4, 13 = Outcome unknown

Start of third trimester vs 24+0 We have specified still birth/live birth based on the start of the third trimester. Babies are viable from 24+0 weeks (and terminations after this point very rare and usually for birth defects incompatible with life). CPRD consider 3rd trimester from 27+0. @finersarah @f-eto Should we consider live birth/still birth after 24+0 weeks gestation. I think we would need to calculate this based on the estimated start date of pregnancy.

Thanks,

M

Fabiola-Eto commented 2 years ago

@Miriam-S-git thank you so much for your inputs on this.

@Miriam-S-git or @finersarah please, forgive my question, but would you mind clarifying why are we looking at pregnancies that reached the third trimester? Wouldn't our goal be to look at how many pregnancy episodes each woman had and/or the outcome of each episode? If so, there is a variable that gives us that information (totalpregs - Total number of identified pregnancy episodes (per woman)). Also, it is possible to check the outcome of each pregnancy episode individually. Alternatively, there is a variable that gives us the estimated duration of pregnancy episode in days (calculated as pregend minus pregstart (gestdays)).

Wouldn't we be interested in seeing if the number of pregnancy episodes and their outcomes influence the pattern or trajectory of multimorbidity in women? Please, do correct me if I am wrong. Thanks.

Miriam-S-git commented 2 years ago

HI, @f-eto @finersarah

Thanks Fabiola. I think that all the above are good thoughts. There is a lot of very useful information in the pregnancy dataset.

I identified the codes to calculate pregnancies reaching the third trimester/24 weeks (still birth/live birth) as this was what was put in the CPRD application. (I think we structured the original CPRD application that way due to the complexity of identifying early pregnancy solely using primary care data, but as the pregnancy register uses more data sources, therefore we can assess things like early pregnancy a lot more reliably).

I guess it will just depend on what data exactly should and can be put into the longitudinal models as an exposure. This may take quite a lot of thought as the data could get quite complex.

M