Is achondroplasia (dwarfism) a genetic defect?

Q: I am 30 years old and 15 weeks pregnant. Last time I had a blighted ovum which naturally miscarried in about 8/9 weeks. This time I went for an early scan and I was told that it is normal. My question is - I have a sister-in-law who has achondroplasia (dwarfism). Me and my husband are both very tense at this situation and we decided to have a triple test done. I want to ask since my sister-in-law is having achondroplasia which is caused by the abnormalities within the chromosomes, will my child have an additional risk of chromosomal abnormalities? Will I be able to carry a normal baby?

A:Triple test is to find out whether the fetus has Down syndrome or neural tube defect. It will not test for achondroplasia. Your risk of having a baby with achondroplasia is like the risk of any one else in the general population, i.e. about 1 in 30,000. The risk is increased if:1. The diagnosis in the affected child is definitely achondroplasia.2. None of you have any such problem.