Aiyoo, I totally understand your worry! Honestly, this is really something best discussed with your OB/GYN directly, they know your full medical history and can give you the most accurate answer for your pregnancy, okay? That said, a few of us mums in my circle took our boosters during pregnancy without issues, but everyone's situation is different. Your doctor will advise what's safest for you and baby at 18 weeks. Don't hesitate to call your clinic before the 26th if you're nervous, they're used to these questions!