Bpd dating pregnancy
Bpd dating pregnancy
In the past gestational age was established by a combination of the historical information and the physical examination.Reliance was placed on the menstrual history and the maternal sensation of fetal movement (“quickening”).
Test results are interpreted based on Liley's zones relative to gestational age.The sac is measured inside the hyperechoic rim, including only the echo-free space (Fig. The gestational sac is imaged first in the longitudinal plane, obtaining long axis and anteroposterior measurements perpendicular to each other. The longitudinal diameter is measured between the small crosses (1) and the anteroposterior diameter is measured between the larger crosses (2). Transverse image obtained at the level of the anteroposterior diameter.Then, in the transverse plane at the level of the anteroposterior measurement, the width measurement is obtained. The transverse diameter is measured between the crosses.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.Clearly, the inaccuracies of history and physical examination may limit their usefulness in assessment of gestational age.
Methods that assess the time of ovulation or conception can accurately establish gestational age.
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).
In another report, even among women with known LMP, neonatal age assessment differed markedly from that assigned by certain menstrual dates in 15%.
Bimanual examination in the first trimester may be accurate within ±2 weeks; however, fundal height measurement, which is more commonly used to assess gestational age, is only accurate within ±4 to 6 weeks.
Both parameters are useful because each measures a different aspect of the first-trimester pregnancy and may be used at different times during the first trimester.