I have a dataset which contains pregnancy, maternal, foetal and children data and I am developing a predictive machine learning model to predict adverse pregnancy outcomes.
The dataset contains mostly features with a single value per pregnancy, e.g. maternalObesity = ["Yes", "No]. However, I have some features that have multiple values per pregnancy, such as the foetal abdominal circumference and estimated foetal weight which have been recorded multiple times at different times during gestation (so each pregnancy will have between 1 and 26 observations for these features each), like so:
PregnancyID gestationWeek abdomcirc maternalObesity
1 13 200 Yes
1 18 240 Yes
1 30 294 Yes
2 11 156 No
2 20 248 No
So in pregnancy 1, we can see that the abdominal circumference was recorded 3 times at weeks 13, 18 and 30.
All questions I have seen here which have addresses the issue of multiple values per sample have been about categorical features, like this and this. Here the suggested solution was to OneHotEncode the features. However, like I said, this does not apply in my case as I have continuous (float) variables.
I have spent the last few months attempting different methods to best handle these features such that I don't lose any valuable information. Simply adding these features into in my dataset will result in almost duplicate rows as the vast majority of my samples have single values (like in the table above.
Here are some of the different approaches I have considered to handle these features:
Derive statistical values from the features, like here. So I compute mean the maximum, minimum, variance, range, etc. of all the observations per pregnancy. However, the downfall with this approach is that the time at which the values are recorded is neglected. The time of the measurement may be significant as a higher abdominal circumference earlier in pregnancy may be more correlated with the adverse outcome I am trying to predict.
Summarise the measurements into a fixed number of features by grouping them into 3 trimester, like here. So I can group all measurements by 3 trimesters, and each feature would hold the maximum measurement recorded during that trimester.
So my dataset will look like this:
PregnancyID MotherID abdomCirc1st abdomCirc2nd abdomCirc3rd
1 1 200 315 350
2 2 156 248 NaN
This approach takes into account the time range of the measurement, but will result in a lot of NaNs in the new features, as many pregnancies do not have a measurement for each trimester. Also, the maximum may result in some statistical information being lost, unlike approach 1.
- I initially thought about using a python list for these features. However, I do not know if a machine learning model can handle this data type, and again, the time each measurement was taken is neglected in this approach.
So my data will look something like this:
PregnancyID maternalObesity abdomcirc
1 Yes [200, 240, 294]
2 No [156, 248]
In conclusion, I need some guidance as I have found a lack of examples and resources out there about this issue. So please advise what the best approach is in this case and if there are any detailed examples out there that address this issue I would appreciate it.