Maternal Serum Testing (Triple Marker)

The California Expanded AFP (XAFP) program is administered by the California DHS

REFERRAL

• Singleton > 2.5 MoM for NTD
• Twins with > 4.5 multiples of the median (MoM)  for NTD
• Twin with one  demised twin where demise occurred less than 3 weeks from the time of blood collection with  > 4.5 MoM for NTD
• Twin with one  demised twin where demise occurred greater than or equal 3 weeks at blood collection with > 2.5 MoM for NTD (same as singleton)
• Risk for Down syndrome 1 in 190  on the XAFP screen
• Risk for trisomy 18 (Edward syndrome)  1 in 100 on the XAFP screen
• Risk for Smith-Lemli-Opitz syndrome 1 in 50 on the XAFP screen.
• H/O neural tube defect (NTD):
  • Previous child with an NTD
  • sibling or half-sibling of fetus with an NTD
  • parent of a fetus with an NTD
  • Two second degree relatives of a fetus with an NTD.
• A history of exposure to valproic acid( Depakote, Depakene) or carbamazepine (Tegretol, Carbatrol) during the first trimester or one month prior to conception.

Decimal/weeks to Days Conversion

Decimal weeks	Days
16.1	1 day
16.2	1 day
16.3	2 days
16.4	3 days
16.5	4 days
16.6	4 days
16.7	5 days
16.8	6 days
16.9	6 days

RECOMMENDATIONS FOR FOLATE

• 400 micrograms daily for all women of childbearing age.
• 4 milligram daily two months prior to conception and during the the first trimester for women with a previous pregnancy complicated by neural tube defect (NTD)

REFERENCE:Expanded AFP Screening Program Prenatal Care Provider Handbook. Sacramento, CA: California Department of Health Services, Genetic Disease Branch; 1997.
 

RECURRENCE RISK(%) FOR COMMON MULTIFACTORIAL CONDITIONS [5]

*For congenital heart disease if the mother is the affected parent the risk is as for two sibs

COUNSELING: For multifactorial conditions, ask the parents if they have any ideas regarding the cause of the defect. The developmental pathology of the defect should be explained to the parents . Explain that the recurrence risk for a similar defect is generally 3 to 5 % (or the square root of the population incidence) if one offspring is affected. The recurrence risk is increased if:

The risk to a second degree relative (includes half brother or sister) is closer to the population incidence.

REFERENCES

1. Cuckle HA, Wald NJ, Thompson SC.Estimating a woman’s risk of having a pregnancy associated with Down’s syndrome using her age and serum alpha-fetoprotein level. Br J Obstet Gynaecol 1987 94:387

2. Data from (1) adjusted for 23% loss rate: Hook, EB. Chromosome abnormalities and spontaneous fetal deaths following amniocentesis:further data and associations with maternal age. Am J Hum Genet 1983 35:110-116

3. Estimate from Foundation for Blood Research

4. Hook EB, Cross PK, Schreinemachers DM.Chromosomal abnormality rates at amniocentesis and in live-born infants. JAMA 1983 249:2034-203

5. Laxova R, Feldman PF. General Genetics Principles: Chromosomal, Mendelian, and Principles of Teratology.  In: ed Gleicher N Principles and Practice of Medical Therapy in Pregnancy Norwalk CT: Appleton & Lange, 1992. p143.