Early ultrasound gestational age dating

The accuracy of menstrual history in women with a history of oligo-ovulation, such as those with polycystic ovarian syndrome, should be questioned.

If conception occurred while oral contraceptives or long-acting progestogens were being taken, the LMP cannot be used because it has no relation to the time of ovulation.

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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 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.

Gestational age (GA) refers to the length of pregnancy after the first day of the last menstrual period (LMP) and is usually expressed in weeks and days. Conceptional age (CA) is the true fetal age and refers to the length of pregnancy from the time of conception.

This terminology does vary geographically and over time, and it may need clarification if not explicitly defined in relevant articles.In normal pregnancies, the length of gestation is minimally affected by maternal characteristics.However, obese women are significantly more likely to go post-term.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 expected date of delivery (EDD) is one of the earliest pieces of information a pregnant woman requests once pregnancy is confirmed.

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