Abstract
ObjectivesTo investigate why episodes of pregnancy identified from electronic health records may be incomplete or conflicting (overlapping), and provide guidance on how to handle them.SettingPregnancy Register generated from the Clinical Practice Research Datalink (CPRD) GOLD UK primary care database.ParticipantsFemale patients with at least one pregnancy episode in the Register (01 January 1937−31 December 2017) which had no recorded outcome or conflicted with another episode.DesignWe identified multiple scenarios potentially explaining why uncertain episodes occur. Criteria were established and systematically applied to determine whether episodes had evidence of each scenario. Linked Hospital Episode Statistics were used to identify pregnancy events not captured in primary care.ResultsOf 5.8 million pregnancy episodes in the Register, 932 604 (16%) had no recorded outcome, and 478 341 (8.5%) conflicted with another episode (251 026 distinct conflicting pairs of episodes among 210 593 women). 826 146 (89%) of the episodes without outcome recorded in primary care and 215 577 (86%) of the conflicting pairs were consistent with one or more of our proposed scenarios. For 689 737 (74%) episodes with recorded outcome missing and 215 544 (86%) of the conflicting pairs (at least one episode), supportive evidence (eg, antenatal records, linked hospital records) suggested they were true and current pregnancies. Furthermore, 516 818 (55 %) and 160 936 (64%), respectively, were during research quality follow-up time. For a sizeable proportion of uncertain episode, there is evidence to suggest that historical outcomes being recorded by the general practitioner during an ongoing pregnancy may offer explanation (73 208 (29.2%) and 349 874 (37.5%)).ConclusionsThis work provides insight to users of the CPRD Pregnancy Register on why uncertain pregnancy episodes exist and indicates that most of these episodes are likely to be real pregnancies. Guidance is given to help researchers consider whether to include/exclude uncertain pregnancies from their studies, and how to tailor approaches to minimise underestimation and bias.
Highlights
A new, longer offset 3D dataset was acquired in 1999 to replace the original pre-development 1986 3D seismic volume
A revised interpretation of the crestal portion of the Judy structure was completed. This new interpretation was coupled with the results from a detailed review of the geochemical, pressure and fault seal data, to create a petroleum charge model which accounted for the variations in fluid types and contacts throughout the field and identified three fault blocks (30/7a-P16, P17 and P18) in the crestal portion of the field for infill drilling
The Judy Field consists of a series of tilted pre-Cretaceous fault blocks, which contain hydrocarbons in the Upper Jurassic Fulmar Formation and the Joanne and Judy Sandstone Members of the Triassic Skagerrak Formation
Summary
Of the Skagerrak Formation (Goldsmith et al 1995) (Fig. 3). Hydrocarbons have been discovered in the Upper Jurassic Fulmar Formation but are volumetrically insignificant since this interval is thin and laterally discontinuous. The channel sandstones are interpreted to represent the deposits of ephemeral fluvial channels and, each of the finingupward sequences may represent a single flood event characterized by incision and filling of a shallow, low sinuosity channel (Tunbridge 1984; Olsen 1987; Sadler & Kelly 1993) They exhibit the best reservoir quality, with an arithmetic mean helium porosity of 27% at ambient conditions and horizontal air permeability (Kh) of 1100 mD (Fig. 4). Lacustrine mudstones comprise argillaceous and micaceous sediments which are interpreted to have been deposited at the margins of desert lakes or on the interfluves of the channels They have the lowest average porosity and Kh but can be as high as the argillaceous sandstone since they grade laterally into that facies association (Fig. 4).
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