Universal prenatal screening: a initiative from Guanajuato, Mexico to improve equity in perinatal healthcare

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TL;DR

This paper describes the design and implementation of a universal prenatal screening care model (CETO) in Guanajuato, Mexico, aimed at providing equitable perinatal healthcare to uninsured pregnant women. The model uses a horizontal, multiparametric ultrasound-based screening approach across all three trimesters, performed by trained general practitioners and supervised by maternal-fetal specialists, to identify risks for preeclampsia, preterm birth, fetal growth restriction, and congenital anomalies. From 2018 to 2020, the center performed 17,693 prenatal screenings, covering 43.3% of the target population, and demonstrated increasing detection rates for preeclampsia (from 0.9% in 2011 to 1.9% in 2019) while reducing rates of fetal growth restriction and prematurity.

Full summary

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**Background:** Maternal and child health indicators reflect healthcare quality, yet low- and middle-income countries face barriers in implementing prenatal screening due to limited resources for biochemical markers and cell-free fetal DNA. In Mexico, the healthcare system is fragmented, with half the population lacking social security. Guanajuato state has a maternal death ratio of 38.8 per 100,000 live births, higher than the national ratio of 30.5 per 100,000. Leading causes of maternal death are preeclampsia-eclampsia (18%), obstetric hemorrhage (17.4%), and abortion (7.1%). In 2020, 22,637 fetal deaths were registered nationally (rate 6.7 per 10,000 women of childbearing age), with 82.9% occurring before delivery. Infant mortality in Guanajuato is primarily due to perinatal conditions (rate 4.9 per 1,000 live births) and congenital malformations (rate 3.0 per 1,000 live births). The existing Mexican standard (NOM 007) mandates only three routine ultrasounds without integrating risk factors or biophysical parameters.

**Methods:** The State Center for Timely Prenatal Screening (CETO) was established in 2014 as a multicentric center under the Institute of Public Health of Guanajuato. The model provides screening to pregnant women without formal employment or health insurance. First-trimester screening (11–13.6 weeks) includes extended ultrasound markers (nuchal translucency, nasal bone, tricuspid flow, ductus venosus flow, uterine artery Doppler, cervical length) plus detailed anatomical evaluation. Second-trimester screening (18–22 weeks) focuses on structural anomalies and re-evaluation of preeclampsia and preterm risk. Third-trimester screening (after 28 weeks) detects late-onset placental diseases. General practitioners certified by The Fetal Medicine Foundation perform initial screenings at six primary care units across two health jurisdictions (VII and VIII). High-risk patients are referred to the central unit at the Maternal and Child Hospital of Leon for specialized follow-up in dedicated clinics: placental disease, prematurity prevention, multiple gestations, soft markers for aneuploidy, fetal pathology, perinatal genetics, fetal cardiology, fetal neurology, and psychology. The center has 13 high-resolution GE Voluson ultrasound units, Viewpoint software for data integration, and an electronic scheduling system. Inter-institutional collaborations with third-level hospitals in other states provide access to fetal surgery.

**Key Results:** From January 2018 to December 2020, the center performed 17,693 prenatal screenings, covering 43.3% of the estimated 40,797 pregnancies in the target population. Productivity by work lines included: 1,919 first-trimester scans, 8,605 second-trimester scans, 3,083 third-trimester scans, 2,911 complementary high-risk first-trimester scans, 5,773 preterm prevention consultations, 1,805 placental disease consultations, 1,458 multiple pregnancy evaluations, 1,407 soft marker evaluations, 1,460 fetal pathology evaluations, and 313 invasive procedures (amniocentesis, cordocentesis, or chorionic villus biopsy). Coverage of main perinatal outcomes showed increasing detection of preeclampsia from 489 cases (0.9%) in 2011 to 1,000 cases (1.9%) in 2019. Fetal growth restriction detection decreased from 482 cases (0.9%) in 2011 to 173 cases (0.3%) in 2019. Prematurity detection decreased from 352 cases (0.7%) in 2011 to 141 cases (0.3%) in 2019. Birth defect detection decreased from 471 cases (0.9%) in 2011 to 314 cases (0.6%) in 2019.

**Clinical Implications:** This horizontal care model demonstrates that comprehensive prenatal screening can be implemented in middle-income settings without biochemical markers or cell-free fetal DNA by maximizing ultrasound parameters and using a risk-based triage system. The model leverages primary care general practitioners for broad coverage while ensuring specialist oversight for high-risk cases. The approach addresses key causes of perinatal mortality—preeclampsia, preterm birth, fetal growth restriction, and congenital anomalies—through early identification and preventive interventions (e.g., acetylsalicylic acid for preeclampsia, progesterone/cerclage/pessary for prematurity). The model's replicability in other Mexican states and emerging economies could improve equity in perinatal healthcare access. Limitations include the absence of biochemical markers and cell-free fetal DNA, reliance on continuous training and certification of general practitioners, and the need for subsequent studies to verify outcomes.