At 5-8 weeks a bradycardia (less than 90 bpm) is associated with a high risk of miscarriage.
Many women do not ovulate at around day 14, so findings after a single scan should always be interpreted with caution.
3.5 to 7 million cycles per second) are generally used for this purpose.
They are emitted from a transducer which is placed in contact with the maternal abdomen, and is moved to "look at" (likened to a light shined from a torch) any particular content of the uterus.
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).
a) The Crown-rump length (CRL) This measurement can be made between 7 to 13 weeks and gives very accurate estimation of the gestational age.
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.
(Table) An important point to note is that when the due date has been set by an accurately measured CRL, it should not be changed by a subsequent scan.
For example, if another scan done 6 or 8 weeks later says that one should have a new due date which is further away, one should not normally change the date but should rather interpret the finding as that the baby is not growing at the expected rate.
b) The Biparietal diameter (BPD) The diameter between the 2 sides of the head. It increases from about 2.4 cm at 13 weeks to about 9.5 cm at term.
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.
Ultrasound can also very importantly confirm the site of the pregnancy is within the cavity of the uterus. A visible heartbeat could be seen and detectable by pulsed doppler ultrasound by about 6 weeks and is usually clearly depictable by 7 weeks.