FASA (Fetal Anatomic Sex Assignment)

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Accurate fetal sex determination can be performed by visualization of the external genitalia of the fetus. Fetal sex determination by ultrasound is performed routinely as part of a comprehensive assessment of the fetus and placenta. All of the information usually included in a report for an obstetrician is immediately available to you at the time of your visit. Details of the health and sex of your unborn baby are demonstrated to you during the ultrasound exam. A VHS videotape with the doctor's voice narration can be made at the time of the exam at no extra charge. The VHS videotape is yours to keep as an electronic souvenir.

Seeing the developing fetus may enhance your bond. Knowledge of the sex of the fetus also may further enhance bonding.

Please let us know if you do not want to know the sex of the fetus.

What is FASASM?

FASASM stands for Fetal Anatomical Sex Assignment, a procedure developed by John D. Stephens, M.D., FACOG. He has over 26 years experience doing obstetric ultrasound scanning. By using the method he has patented in the U.S., he is able with 100% guaranteed accuracy to tell you the sex (gender) of your unborn fetus from the third month onwards in pregnancy. We currently have an obstetric and sonography office in Blaine, WA.

This painless and safe method of ultrasound scanning, which has been over the years approved by both the medical authorities in the U.K. and the United States as totally safe, can help you as the parents of the unborn fetus to bond with your baby. As well as finding out the sex of the baby for you, we do a full health check on the baby to put at rest any fears you might have.


Accuracy of the technique of fetal sex determination by ultrasound (100%) was first established in 1983, when sex predicted by ultrasound was compared to subsequently obtained sex of the chromosomes obtained from genetic amniocentesis ("essentially 100% accuracy" New England Journal of Medicine, October 20, 1983).

  • A new technique, FASASM permits accurate fetal sex determination of a male and female at 12 weeks of gestation age (GA) (from the first day of the last day of the last menstrual period).
  • 100% accurate.


No harmful effects of real time ultrasound have been shown in ongoing studies in the United States, Canada and Europe. Your doctor can explain why an ultrasound examination is recommended.


It is routine recommendation to have an ultrasound examination throughout pregnancy to study the fetus for reassurance. In early pregnancy, ultrasound is used to accurately date the pregnancy, to check for twins and also check the early development for reassurance. At Koala Labs in Blaine, WA, we perform this examination during 12-14 weeks of GA. There are good reasons for having ultrasound in the first and also second and third trimester.

The external genitalia of the fetus appears to be identical at 10 weeks from the first day of the L.M.P. occurs over the following two weeks. It becomes possible to accurately (100%) determine male and female in the 12th week of GA. If the pregnancy is less than 12 weeks from the L.M.P., a repeat FASASM sonogram may be needed to provide the 100% accuracy.

Those couples that wish to have a FASASM should have had their appointment based upon having had a prior dating ultrasound study. There are many reasons for having an ultrasound in the first trimester. A prior ultrasound study is highly necessary for those people traveling long distances. This will ensure that your FASASM study will be performed in the 12-14 weeks G.A. from the L.M.P. (or 10-12 weeks of fetal age development). In this way, Koala Labs can provide you with the assurance of "essentially 100% accuracy" of the fetal sex determination.

Patent Information

  • United States Patent
  • Patent Number: 4,986,274
  • Date of Patent: January 22, 1991
  • Fetal Anatomic Sex Assignment by Ultrasonography During Early Pregnancy
  • Inventor: John D. Stephens
  • Certificate of Grant of Patent UK
  • In accordance with Section 24(2) of the Patents Act, 1977, it is hereby certified that a patent having the specification no. 2166240 has been granted to John D. Stephens, in respect of an invention disclosed in an application for that patent having a date of filing of 16 October 1985 being an invention for "Fetal anatomic sex assignment by ultrasonography during early pregnancy."
  • Dated this Twenty-first day of June 1989 (Mewburn Ellis & Company patent law firm London, UK)

Form for Early Pregnancy Fetal Anatomic Sex Assignment by Ultrasound (FASA)

Poster for International Symposium on First Trimester Fetal Diagnosis

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