One of the most consistent and best-documented effects of cigarette smoking during pregnancy is

Answer;

Low birth weight.

One of the most consistent and best documented effects of cigarette smoking during pregnancy is low birth weight.

Explanation;

Smoking during pregnancy has various effects on the fetus, causing a baby to be born early or to have low birth weight which makes it more likely for the baby to get sick and stay in the hospital longer.

Additionally; smoking during and after pregnancy is a risk factor of Sudden Infant Death Syndrome.