week and much less the day. They do not afford a more accurate means
of predicting the date of confinement than does quickening. The
evidence gained from the position of the womb, like that afforded by
the beginning of quickening, generally confirms the prediction made
from the menstrual history; it serves only occasionally to correct
it.

PROLONGED PREGNANCY.--Since birth does not occur in many cases until
the predicted date has been passed, it will be helpful even at the
cost of repetition to sum up what we know in explanation of such
unfulfilled predictions. They are to be explained sometimes by
uncertainty as to the beginning of pregnancy, as for example by the
supposition that conception took place shortly after the last
menstrual period, whereas it actually occurred two or three weeks
later. In a few instances, however, errors of observation or of
calculation will not account for false predictions.

It is generally admitted that second pregnancies average somewhat
longer than first pregnancies; one series of statistics indicates
that the duration increases slightly with each pregnancy up to the
ninth and decreases after that. Pregnancy is protracted more
frequently in healthy women than in those who are not, and again more
frequently in those who are inactive than in those who work. With
twins, contrary to the popular belief, pregnancy is apt to end
before, not after, the expected date. The sex of the child, in all
probability, has no influence upon the duration of pregnancy.

As we might expect, individuality is also a factor in this problem.
Thus, the period of gestation with some women is regularly longer,
with others habitually shorter than the accepted average. Until