Pulsed and colour Doppler ultrasound are valuable techniques for placental assessment. Umbilical cord flow can be seen at 7-8 weeks, though end-diastolic flow (EDF) is not established until 14 weeks. Early-onset IUGR pregnancies may be characterized by absent EDF in the umbilical arteries , associated with small malformed placentas, and defective angiogenesis in the gas-exchanging terminal placental villi . Amajor role for Doppler ultrasound in placental assessment is to determine maternal flow in the uterine arteries. This screening test is performed either at the 18-20-week anatomical ultrasound or at a separate 22-week visit . Integration of placental ultrasound, uterine artery Doppler and first + second trimester biochemistry screening tests (PAPP-A, hCG and AFP) is an effective way of screening for serious placental insufficiency syndromes before threatening fetal viability, thereby directing care to a high-risk pregnancy unit .
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The first trimester is very important for the mother and the baby. For most women it is common to find out about their pregnancy after they have missed their menstrual cycle. Since, not all women note their menstrual cycle and dates of intercourse, it may cause slight confusion about the exact date of conception. That is why most women find out that they are pregnant only after one month of pregnancy.