My sister had to have one with her second pregnancy as she lost lumps of blood whenever she moved...

She honestly said it was extremely painful she was 18-19 wks at the time (sorry, but I will tell you what she experienced, as we sat together for a long time during the few weeks of worry)
They did ultrasounds & said the baby was not forming correctly & was severley deformed, as my sister had spent 2 years at Uni studying to be a special needs carer, nurse etc she decided that this is what their destiny was... But her OB recommended the Amnio, she said it was awful & she felt torn, but the fluid that was extracted was thick & black like coffee, it is supposed to be clear apparently...
The baby was drowning itself apparently & had organs growing on the outside of it's body... They told her the baby if delivered would die anyways so after having 1 day to decide they decided the baby would die anyways & to terminate the pregnancy...
She delivered naturally after having gels inserted over a 24hour period, her husband slept beside her in the hospital as she began having contractions & a nurse held her as she delivered their 2nd son..


This is a totally different scenario to what you are going through & my sister went on to have another baby & she is a perfectly healthy 5 yr old now...

I am sure as you said you havent had any other issues during your pregnancy that all will be perfectly fine...
I dont wnat to alarm, you because as I said my sister had been losing chunks of blood the entire pregnancy... They already knew there were problems with the baby but were not aware how severe they were...

I pray for you & will be reading here soon that all is fine!!!

Big hugs & my thoughts arew ith you...

Infact I think Lucy (a mod) had an amnio, maybe search back into the archives as herexperience was not at all like my sisters & everything was fine with her daughter!!!!