You have told that you are 16 weeks pregnant and you smoked weed last night.
First you need to know that fetal (baby) blood circulation and maternal (mother) blood circulation are interconnected by placenta. The placentas contains numerous blood vessels. The baby derives its nutrition from the mother through this placenta. Not only nutrition, but other substances present in the mother's blood may cross the placenta and enter the baby's circulation and can cause adverse effects.
You had this strange reaction and fast beating heart after you have smoked the weed. It's because the products of the smoking
had got absorbed into your blood and caused these effects. So the same products can also cross the placenta and can cause similar effects on the baby.
Also because of smoking the blood vessels in the placenta may constrict and cause decreased blood supply to the fetus (baby) and this can result in intra uterine growth retardation of the fetus.
My advice is to stop smoking during pregnancy
and you need to consult your gynecologist to know the status of the fetus. She can get an Ultrasound
scan to know the fetal status.
Good luck to you.