It must always be considered a possibility in any pregnant woman beyond 20 weeks of gestation.

In humans, this is from the eighth week of gestation.

More than 500,000 babies were born before 37 weeks of gestation, a 2 percent increase over the previous year.

Only 1.4 percent were performed after 21 weeks of gestation.

They were in the 25th week of gestation when born, or approximately 3 months premature.

In humans, this action takes place during the first 8 weeks of gestation.

From the 15th week of gestation until approximately the 26th, other techniques must be used.

The problem occurs during the first four weeks of gestation, often before the mother knows she's pregnant.

The fetus was put on the list at 30 weeks of gestation.

Some however believe it occurs later in development, around the fourth week of gestation.