Outcome dependent growth curves for singleton pregnancies based on birth weight of babies for Polish population

To create outcome dependent fetal growth curves and birth weight standards that can be analyzed for use in clinic specifically for Western European populations.

We conducted a retrospective study on fetal growth and birth weight trends from live birth singleton pregnancies between 2005 and 2018 at one of the largest tertiary gynecologic-obstetric hospitals in Poland. The inclusion criteria were at least 22 weeks of gestation at birth regardless of delivery mode (vaginal or C-section), no congenital anomalies diagnosed before and after delivery and an Apgar score of at least 7 in the first minute. The final sample had a total of 39,413 cases (18,562 girls and 20,851 boys). We presented 7 (for all fetuses in the 5th, 10th, 25th, 50th, 75th, 90th and 95th percentiles) and 6 (for boys and girls each at 10th, 50th and 90th percentiles) fetal growth curves between 25 and 40 weeks of gestation. Birth weight trends were obtained and analyzed from all babies in the 5th, 10th, 25th, 50th, 75th and 95th percentiles born between 22 to 42 weeks of gestation with also separate trends for boys and girls.

The largest differences in fetal growth curves were observed in the 10th and 50th percentiles between 22 and 34 weeks of gestation. A decreasing fetal weight gain pattern was observed between 27 and 30 weeks and after 38 weeks of gestation, the decrease was more drastic in female. A significant increase from 2009 to 2017 was observed in the weight of 50th percentile babies born at or after 35 weeks. We found significant discrepancies between our results and the most used European fetal growth curves particularly in the 10th and 90th percentile weights at 30 weeks.

Separate scales for boys and girls were implied and given the overall difference form commonly used references. We believe there is significant value in using these unique patterns found in fetal growth curves and birth weights of ethnically homogenous population (such as Poland) at everyday clinical practice for more opportunities of safe obstetric care and higher chances of delivering a healthy child.