A First Trimester Prediction Model for Large for Gestational Age Infants: a Preliminary Study

Overview

Large for gestational age infants (LGA) have increased risks of adverse short-term perinatal outcomes. This study aims to develop a multivariable prediction model for the risk of giving birth to a LGA baby, by using biochemical, biophysical, anamnestic, and clinical maternal characteristics available at first trimester. This prospective study includes all singleton pregnancies attending the first trimester aneuploidy screening at the Obstetric Unit of the University Hospital of Modena, in Northern Italy.

For each subject, blood sample is collected in fasting conditions, then centrifuged, and the serum stored at minus 80° C, for subsequent biochemical analyses. PAPP-A, PlGF and Inibin A is measured with the automated DELFIA EXPRESS system (Thermo Fisher Scientific, Perkin Elmer ®). Insulin, high density lipoproteins (HDL) and triglycerides are measured through routine laboratory methods. The mean arterial pressure (MAP) is measured with validated automated devices (Dinamap, BLTV6XX). After the women are seated and allowed to rest for 3-5 min, normal (22 to 32 cm) adult cuffs are fitted to their both arms. This is repeated two times with 1 min break in between. The MAP is calculated with the formula MAP DBP + 1/3(SBP - DBP) 21, where DBP represents diastolic blood pressure and SBP, systolic blood pressure. We calculate the final MAP as the average of all four measurements. Uterine artery Doppler studies including pulsatility index are measured through trans-abdominal ultrasound (Voluson E8 or Voluson E10) examinations. As indicated in Fetal Medicine Foundation (FMF), when carrying out Doppler studies, color flow mapping is used to identify each uterine artery along the side of the cervix and uterus at the level of the cervical internal os. Pulsed wave Doppler imaging is used with the sampling gate set at 2 mm to cover the whole vessel, and care is taken to ensure that the angle of insonation is less than 30°. When three to five similar consecutive waveforms are obtained, PI is measured. The uterine artery mPI is calculated by adding the right and left pulsatility index together, divided by two. All ultrasound and Doppler studies are carried out by a physician who had received the appropriate certificate of competence in the 11-13+6 week scans and Doppler study from the FMF. Data on pregnancy outcome are collected from the hospital maternity records or directly from women if delivered elsewhere. Medical records are reviewed by research associates to obtain anonymized data on mothers (i.e maternal demographics, BMI, age…) and their newborns (birthweight, gender, Apgar score, admission to the neonatal intensive care unit (NICU) and length of stay, neonatal morbidities, and mortality), and are organized in a password protected database.