Question #1 Ultrasound can be a reliable indicator, but really is only as good as the tech doing it. The most reliable indicator is to have the same tech do it every time. Amniotic fluid level normally increases until 28 to 32 weeks then the level usually stays constant until 37 to 40 weeks when the level begins to decline.
Question #2 Amniotic fluid level can be modified by dietary NaCl through maternal water retention which increases maternal plasma volume. NaCl influences water and electrolyte balance during pregnancy (water retention). Differences in dietary NaCl are accompanied by large differences in the daily patterns of maternal urine sodium, urine sodium/potassium ratios, water intake, and urine volume (water retention) and that then increases the maternal plasma volume thereby increasing uteroplacental blood flow. But excessive sodium intake can cause problems for the mom.
Question #3 Certified nurse midwives are held accountable for their patient’s pregnancy outcomes. Poor pregnancy outcomes have been associated with an amniotic fluid volume of 5 or less as it can indicate poor placental perfusion. Your midwife counseled you within her licensure. Perhaps the outcome would have been the same if you had followed their advice to drink more water. Her advice was right on as H2O intake is the biggest contributor to fluid volume. While you feel you drank plenty of water the recommended fluid intake in pregnancy is 3L/day. That is a lot of water. Oral hydration increases the maternal plasma volume thereby increasing uteroplacental blood flow. This in turn influences the amount of amniotic fluid as mom and babe as are essentially a closed unit :<)
Love and laughter, Maureen
Restricted sodium intake can cause problems also. Restricted sodium intake can interfere with adequate maternal blood volume increase. Recommended amounts are 1.5 to 2.3 g/day.
Sounds to me like you corrected the problem yourself and went on to have the birth experience you desired. What an empowered woman you are. By the way; your baby is beautiful.
Listen to your Mommy gut and get your second opinions...I am so glad you listened to yourself. Not all midwives are the same...