Which statement about obstetric dating and assessment is correct
Fetal heart rate tends to vary with gestational age in the very early parts of pregnancy.Normal heart rate at 6 weeks is around 90-110 beats per minute (bpm) and at 9 weeks is 140-170 bpm.Different babies of the same weight can have different head size, therefore dating in the later part of pregnancy is generally considered unreliable.(Chart and further comments) Dating using the BPD should be done as early as is feasible.Movements such as fetal heart beat and malformations in the feus can be assessed and measurements can be made accurately on the images displayed on the screen.Such measurements form the cornerstone in the assessment of gestational age, size and growth in the fetus.It has progressively become an indispensible obstetric tool and plays an important role in the care of every pregnant woman. The embryo can be observed and measured by about five and a half weeks. The viability of the fetus can be documented in the presence of vaginal bleeding in early pregnancy.
Such information would be useful against the interpretation of the scans. In the presence of first trimester bleeding, ultrasonography is also indispensible in the early diagnosis of ectopic pregnancies and molar pregnancies. Determination of gestational age and assessment of fetal size.Repetitive arrays of ultrasound beams scan the fetus in thin slices and are reflected back onto the same transducer.The information obtained from different reflections are recomposed back into a picture on the monitor screen (a sonogram, or ultrasonogram).The diagnosis of missed abortion is usually made by serial ultrasound scans demonstrating lack of gestational development.For example, if ultrasound scan demonstrates a 7mm embryo but cannot demonstrable a clearcut heartbeat, a missed abortion may be diagnosed.
Fetal body measurements reflect the gestational age of the fetus. In patients with uncertain last menstrual periods, such measurements must be made as early as possible in pregnancy to arrive at a correct dating for the patient. In the latter part of pregnancy measuring body parameters will allow assessment of the size and growth of the fetus and will greatly assist in the diagnosis and management of intrauterine growth retardation (IUGR).