For example, with an LMP beginning on June 15, the EDD will be March 22 of the following year. These consist of an outer wheel that has markings for the calendar and an inner, sliding wheel with weeks and days of gestation.They facilitate the estimation of GA and the calculation of the EDD.
The perception of fetal movement by the patient, often referred to as quickening, is a relatively late sign of pregnancy, usually occurring at 19-21 weeks' gestation in nulliparous women and 17-19 weeks' in multiparous women.
Before the advent of pregnancy tests and ultrasonography, quickening was often the method by which a suspected pregnancy was confirmed; however, at present, it has little diagnostic value.
The first 2 are subject to considerable error and should only be used when ultrasonography facilities are not available.
The date of feeling the first fetal movements (quickening) is far too unreliable to be useful.
The estimation of pregnancy dates is important for the mother, who wants to know when to expect the birth of her baby, and for her health care providers, so they may choose the times at which to perform various screening tests and assessments,such as serum screening, assessment of maturity, and induction of labor for postdate pregnancies.
The 3 basic methods used to help estimate gestational age (GA) are menstrual history, clinical examination, and ultrasonography.
Size can be misleading in the presence of multiple pregnancy, uterine fibroids, or a full bladder.
Tape measurement of the symphysis-fundus height may be useful up to 28-30 weeks' gestation, beyond which it becomes too inaccurate for dating.
Pregnant women should be counselled that only 4% of all babies are born precisely on the estimated date of confinement.
Failure to appreciate this may lead to unnecessary maternal anxiety if a pregnancy progresses beyond the EDD.
The quality of these wheels varies, but in general, the larger wheels yield better results.