Question
I had a Down syndrome screening at the local women and children’s hospital, and the gestational age was written as 15+ weeks. At the time of the examination, it was indicated as high risk. A week later, the doctor said to come for an amniocentesis next Monday. After that, I waited for two weeks and went, where the genetic doctor arranged for blood tests and routine blood work, saying that amniocentesis could be done. I went on Monday last week, and the doctor prescribed an ultrasound and told me that it could be done at 18+ weeks pregnant. It was finally my turn to have the ultrasound, but when I lay down, the doctor who performed the ultrasound told me that it was only 17+ weeks, and it was not yet possible to perform the ultrasound; I should come back in a month. So I went to find the doctor in the genetics department, and she said that it might be an error in calculating the gestational age, asked me to show her the first ultrasound when I knew I was pregnant, and calculated that the day of the Down syndrome screening was only 14+ weeks. So she asked me to go to the genetics testing room for another calculation. This morning, they said it was low position, and I am very confused. What should I do? Which gestational week should I use as a reference?
Answer
Generally speaking, gestational age and expected delivery date are calculated based on the last menstrual period. When menstrual cycles are irregular, gestational age should be calculated based on early pregnancy ultrasound results. According to your description above, the actual gestational age should be over 14 weeks, indicating a lower risk for Down syndrome screening, suggesting a small possibility of giving birth to a child with Down syndrome. Therefore, there is no need for amniocentesis or fetal chromosomal testing.