What is the rate of incidence for oligohydramnios?

Oligohydramnios usually happens in the third trimester, though it can happen throughout pregnancy. Studies show that eight percent of women in America have too little amniotic fluid, though only four percent are diagnosed with oligohydramnios. Because amniotic fluid levels naturally decline in the third trimester, it is more common for women experiencing pregnancies over 41 weeks long (post-term) to get oligohydramnios. In fact, around one out of eight women whose pregnancy extends two weeks after her due date can acquire oligohydramnios, putting the baby at greater risk for other complications.