That's always scary. How far along are you, hon? Normally they do a test on what the fluid is. We can even leak urine when pregnant, I hate to say and have watery discharge. So, normally they check your amniotic fluid levels which I assume they did or you and it was fine. So, it likely was not the fluid you were leaking. When is your follow up with your OB?
Oh my goodness, okay. Well, typically if you have lost amniotic fluid and it is not near time for baby, they monitor closely. They should be checking your amniotic fluid level at least weekly. How far along are you?
So, placenta previa is not terribly concerning at the second trimester mark and is not that uncommon. I was in that same boat. For the vast majority of women, the placenta will rise before the end of pregnancy. They will check you to make sure though as you do NOT want to go into labor with placenta previa. That can be deadly to mom as you can bleed out.
But to be losing amniotic fluid at the second trimester mark is worrying. Here is some information https://www.mayoclinic.org/healthy-lifestyle/pregnancy-week-by-week/expert-answers/low-amniotic-fluid/faq-20057964. Make sure to increase your fluid intake. But you need regular monitoring of the fluid.
The down syndrome screening is not related to this and likely when you were given a last ultrasound in which they said you had placenta previa, they checked for the markers that lead to suspicion of downs. You can have the blood tests and they are often routine. I didn't have them but I was an older mom and would have my baby regardless and my age alone might have skewed the test. but that is up to you and your doctor. Most doctors do check or this.
But the biggest concern you have right now today is the low fluid. You need to follow up and begin having that monitored as well as ask your doctor for possible causes for the leak. Let me know what they say!!! Hang in there.
So, have you been back to the doctor for any follow up? Hope all is well with you!
Usually they will send you to a specialist to keep an eye in the fluids and the baby and to check for all of that stuff if you want to be sure everything is okay I would speak with them about seeing a specialist until the baby is born.