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Published online by Cambridge University Press: 01 August 2014
A two-dimensional ultrasonic B scanner is used to diagnose both single and multiple early pregnancy The contact scanning method is used. The patient is required to have a full bladder if she is under 14 weeks gestation. The uterus and the cervix are outlined. Then a search is made for the gestation sac or sacs within the uterine cavity if the cyesis is under 10 weeks. Serial longitudinal and transverse scans are carried out to outline the gestation sacs. The fetal echoes within the gestation sac are seen and the fetal heart rate can be detected using the time-position display (TP). The patients that are studied fall into the following groups: (1) patients who are clinically suspected to have multiple pregnancy; (2) patients who have been on ovulation induction therapy; (3) patients with family history of twins; (4) patients with threatened abortion. The diagnosis of multiple pregnancy during the 11th week is equivocal. After the 12th week gestation the diagnosis is made by visualising the fetal head and the maturity is then estimated by measuring the biparietal diameter. Thus fetal growth can be assessed by carrying out serial biparietal diameter estimations.