Question

Lady using OCP since 5 month. Amenorrhea since last 6 weeks. Which is best to calculate gestational age in this case?

• A. 280 days from LMP
• B. 256 days from LMP
• C. CRL by USG
• D. Abdominal girth

Answer 1

The Correct Option is C

In the context of calculating gestational age, especially when there's a history of being on oral contraceptive pills (OCP) and amenorrhea, traditional methods based on the Last Menstrual Period (LMP) might not be reliable. Here’s the reasoning for each option:

1. 280 days from LMP: This method assumes regular menstrual cycles, which can be disrupted while using OCPs. Hence, it's not reliable in this case.
2. 256 days from LMP: Similar to the 280-day method, this also relies on regular cycles, making it unsuitable for the same reasons when OCPs affect cycle regularity.
3. CRL by USG: Crown-Rump Length (CRL) obtained from an ultrasound (USG) provides an accurate measurement of the gestational age during the first trimester. It is not dependent on menstrual history, making it the most reliable option when menstrual cycle information is compromised.
4. Abdominal girth: This is not a standard or accurate method for determining gestational age.

Therefore, the best method to calculate gestational age in this scenario is CRL by USG.