Early Obstetric Ultrasound
Preferably done by the vaginal route, this ultrasound helps in correct dating of the pregnancy, located the cardiac activity, ruling out twin pregnancy and ectopic pregnancy. It is especially helpful in pregnant women who have bleeding or pain abdomen.
This is a specialised ultrasound done at 11-13 weeks where specific measurements of the fluid behind the neck spine and the presence of nasal bone is noted. It is combined with blood test( Dual marker) at the same sitting. It is done to rule out mental retardation in the baby due to chromosomal defects. Like down syndrome ,paten & Edward syndrome.
All pregnant women should have a detailed anomaly ultrasound between 18-20 weeks to evaluate the physical, mental and cardiac status of the baby. It takes around half hour to do this ultrasound. In case of presence of any malformation which is in compatible with life, termination can be considered at this time as per Indian MTP low.
Late Obstetric Ultrasound
During the course of pregnancy 2-4 ultrasounds may be done to assess the growth, weight gain, fetal well being, function of the placenta and the amount of liquor.
These parameters help in deciding the plan of pregnancy care.
In high risk pregnancies, the fetal well being is assessed by certain parameters which are noted in form of a score. It helps in decision for mode and time of delivery with the sole aim of delivering a healthy uncompromised baby.
It is a comparatively new modality of assessing the fetal well being and placental function. Here, the blood flow to the baby is assessed by color Doppler in the umbilical vessels and brain. It is vital aid in surveillance and decision for delivery in pregnancies which are at high risk like small for date pregnancy, decreased liquor, high blood pressure or diabetic women.