Early fetal movements are useful for estimating the gestational weeks in the first trimester of pregnancy.

We report usefulness of early movements for evaluating the functional development of human fetuses. The movements were classified into seven patterns and named as follows; "rippling", "small twitch", "twitch", "strong twitch", "float", "swim", and "jump". Relationship between classification and the menstrual age, or the distribution of crown-rump length are presented. The results indicate that the characteristic fetal movements are "rippling" at 8 weeks, "small twitch" around 9 weeks, "twitch" at the beginning of 9 weeks, "strong twitch" at 9 1/2 weeks, "float", "swim", and "jump" at 10 weeks or later.