Prenatal diagnosis and screening is the testing for diseases or conditions in a fetus or embryo before it is before.
Purpose
It aims to detect birth defects e.g. neural tube defects, Down syndrome, chromosome abnormalities genetic disorders and other conditions, e.g. spina bifida, cleft palate, Tay Sachs disease, sickle cell anemia, thalassemia, cystic fibrosis, muscular dystrophy, and fragile X syndrome
Screening can also be used for prenatal sex discernment
Sometimes, the tests are administered to determine if the fetus will be aborted, though doctors and patients also find it useful to Dx high-risk pregnancies early so that delivery can be scheduled in a tertiary care hospital where the baby can receive appropriate care
Methods
Non-invasive (NIPT), including:
Before implantation:
Preimplantation genetic diagnosis, where during IVF procedures, cells are sampled from human emryos before implantation. It is in itself non-invasive, but IVF usually involves invasive procedures e.g. transvaginal oocyte retrieval
Trimester 1:
Fetal cells in maternal blood (FCMB), which is based on enrichment of fetal cells which circulate in maternal blood. Since fetal cells hold all the genetic information of the developing fetus, they can be used to perform prenatal Dx
Cell-free fetal DNA in maternal blood, which is based on DNA of fetal origin circulating in the maternal blood. Testing can potentially identify fetal aneuploidy, and gender of a fetus as early as 6 weeks into a pregnancy. Fetal DNA ranges from about 2-10% of total DNA in materna blood. It also allows whole genome sequencing of the fetus, thus determining the complete DNA sequence of every gene
Trimester 1 or 2:
Ultrasound detection (aka dating scans, booking scans), which is done from 7 weeks to confirm pregnancy dates, and look for twins
The specialized nuchal scan at 11-13 weeks may be used to identify higher risks of Downs syndrome
Later morphology scans from 18 weeks may check for any abnormal development
Fetal heartbeat, which is listening to the fetal heartbeat
Trimester 3:
Non-stress test, using a CTG during trimester 3, to monitor fetal wellbeing
Less invasive:
Trimester 1:
Transcervical retrieval of trophoblast cells, involving cervical mucus aspiration, cervical swabbing, and cervical or intrauterine lavage, can be used to retrieve trophoblast cells for Dx purposes, including prenatal genetic analysis. Success rates range from 40-90%. It can be used for fetal sex determination and identify aneuploidies
Trimester 1 or 2:
Maternal serum screening, including;
Beta-hCG
PAPP-A
Alpha fetoprotein
Inhibin-A
More invasive:
After 10 weeks:
Chorionic villus sampling (see page)
After 15 weeks:
Amniocentesis (see page)
At 24-34 weeks:
Percutaneous umbilical cord blood sampling, a Dx genetic test that examines blood from the fetal umbilical cord to detect fetal abnormalities
Medicinenet.com Word of the Day Medicinenet.com Daily News
Medpage Today Latest Medical News
Health.com Happy & Healthy
Medical News Today headlines
Internal Medicine Clinical News
Modern Medicine News Modern Medicine Feature articles
Cleveland Clinic Journal of Medicine
BMJ Latest news BMJ Latest research BMJ Education
JAMA Current issue
The Lancet Current issue
NEJM Current issue
ScienceMag Current issue
NIH PubMed Health Featured reviews
ABC Health news ABC Health & Wellbeing ABC Health Minutes ABC RN's The Health Report ABC All in The Mind
BBC News - Health (International)
NSW Health Minister for Health Minister for Mental Health NSW Health Publications AI of Health & Welfare Publications Department of Health Publications
WHO Health news WHO Emergencies, disasters news WHO Disease Outbreaks WHO Health feature stories