One should follow a certain guideline for any specific situation. For example for a certain age of pregnancy, or a certain age of a newborn or infant there are defined scores in physical examination or normal activities or .. to be observed. 

My current opnion is under publication but my recommandation:

Pregnancy care protocol: (not depend on maternal age but all times RR measurement is necessary on the booth upper limb)

Get EHR/FHR on the early pregnancy if low or high there will be a high risk pregnancy.

Get biochemisty to observe maternal blood at 8 weeks. (GP or OBS)

Get the CRL at 10th of pregnancy, and use these date to calculate the real GA.

Do an extended fetal scan between 11-14+6(13+6 if you follow FMF criteria). (here you can follow-up the longbones FL and HL (early IUGR) and BPD+IT (neural defects) and NT+DVPI+facial marker (trisomy). (High risk --> NIPT or invasive procedure)

Do biometry scans every 4-to-6 weeks in the second trimester to find to increasement of the values.

3rd trimester depends on the local infrastructure.

Prevention:

Folates - neural tude and cardiac defects,

B6- againgst pregnancy symptoms

aspirin - preeclapsia

Omega-3 acids: IQ incresement

Combined: O3 and folates can decrease the rate of autism (preliminary results)