lust dating - Accuracy of ultrasound dating

In the past gestational age was established by a combination of the historical information and the physical examination.

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Some of the reasons for this uncertainty include oligomenorrhea, metrorrhagia, bleeding in the first trimester of pregnancy, pregnancy following use of oral contraceptives or intrauterine devices, and becoming pregnant in the postpartum period.

Hertz and co-workers reported that menstrual history was considered reliable in only 18% of women.

In vitro fertilization, with known date of conception, is likely the most accurate means of predicting gestational age (±1 day).

However, in most pregnancies, the date of ovulation or conception cannot be as accurately predicted as outlined above and gestational age must be established by other methods.

Other factors include assessment of uterine size by bimanual examination in the first trimester, initial detection of fetal heart tones by Doppler (10–12 weeks) or auscultation (19–21 weeks), and uterine fundal height measurement.

However, both the history and the findings on physical examination are fraught with error, even in the best of circumstances (Table 1).

Proper decisions regarding presumed preterm labor or postdate pregnancies are only possible when gestational age is accurately estimated.

Likewise, timing of repeat cesarean section requires accurate assessment of dates.

Fetal heart rate reactivity and fetal breathing develop with advancing gestational age; therefore, the absence of these biophysical parameters may be interpreted as abnormal for fetuses in whom the gestational age has been overestimated.

Obstetric management is also dependent on gestational age.

Gestational age, synonymous with menstrual age, is defined in weeks beginning from the first day of the last menstrual period (LMP) prior to conception.

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