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Development of a prenatal genetics program at the southeast of Mexico

Prenatal Genetics
  • Primary Categories:
    • Prenatal Genetics
  • Secondary Categories:
    • Prenatal Genetics
Introduction:
The need for prenatal diagnosis after an abnormal ultrasound is a growing need in developed and developing countries. Fetal-free DNA in plasma is a good screening tool for chromosomal disorders and has been uptake in Latin-America in private medicine. However, few dedicated prenatal genetic diagnosis programs are established in the private sector of Latin-American countries like Mexico and these are limited in offering the full blown of genetic evaluations available in developed countries.

Mexico has a reach tradition in medical genetics with 55 years of residency program in clinical genetics. The first reports of prenatal diagnosis by amniocentesis in Mexico came in 1986, the fetal diagnosis programs were focused on chromosomal disorders and mainly based at Mexico City. The expansion of maternal fetal medicine specialists across Mexico has open an improvement in detection of fetal abnormalities, but still lacking dedicated prenatal genetics programs and expertise outside big cities.

We describe the implementation of a prenatal genetics program serving patients with fetal abnormalities from Yucatan peninsula at the southeast of Mexico

Methods:
Retrospective cohort study from September 2020 to September 2024 of pregnancies at risk of genetic disorders or with abnormal prenatal ultrasounds who had diagnostic procedures (amniocentesis, CVS) or terminations of pregnancy with DNA extraction from skin biopsies.

In our program patients are referred by gynecologists mainly from the 3 states (Yucatan, Campeche and Quintana Roo) comprising Yucatan´s peninsula. The population living in this region corresponds to approximately 5 million habitants. All patients were evaluated initially by maternal fetal medicine specialist who performed a Level II ultrasound for characterize fetal phenotype. After MFM evaluation and ultrasounds all patients were referred to a clinical geneticist who evaluated the case and decided appropriate diagnostic genetic testing (karyotype, microarray, gene panel, exome) and follow-up according to a possible diagnosis and financial resources of the family. Genetic testing was performed in CLIA or CAP certified laboratories. Geneticist attended all terminations for deep phenotyping of the fetus.

Results:
Our cohort corresponds to 78 diagnostic procedures of prenatal genetics, including 59 amniocentesis, 9 CVS and 10 pregnancy terminations with DNA extraction. For amniocentesis fetal age was from 16 to 32 weeks of pregnancy main indications were increased nuchal translucency, cystic hygroma, abnormal extremities and heart malformations. Different approaches for genetic testing were used including karyotype, microarray, fast FISH for common trisomies, gene panels and exome in different combinations. The most common cytogenetic abnormality was trisomy 18, followed by trisomy 21, one twin pregnancy was mosaic for trisomy 18 in both fetuses and other mosaic for trisomy 13 detected by microarray. For exomes pathogenic variants were found in PTPN11 and NRF2 and a VUS in PITX2 in a fetus with porencephaly and microphthalmia detected at birth. One fetus with increased nuchal translucency was found with a missense TEK variant and a novel premature stop in PKD1 probably inherited from mom affected by polycystic kidney disease.

In terminations of pregnancy, genetic diagnosis included Ellis-van Crevel syndrome by homozygous variant leading to a premature stop in EVC, two fetuses with skeletal dysplasia with FGFR3:p.Tyr373Cys associated to thanatophoric dysplasia, and trisomies 18 and 21.

Conclusion:
Despite 37 years of genetics in Yucatan, only teamwork with gynecologists and maternal fetal medicines specialist allowed flourishing a dedicated prenatal genetics program. Our experience highlights the challenges of setting up a prenatal diagnosis program in the private sector of a developing country. 

Our program is nourished by activities in public and private hospitals, shows the critical role of developing new poles of maternal medicine and prenatal genetics and benefits an underserved population of mainly Mayan origin. It also highlights the relevance of diversity for advance prenatal genomics approaches.

 

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