Abstract:

Objective

The aim of this study is to quantify the retinal vascular tortuosity，retinal vascular diameter and retinal morphological characteristics in normal pregnant women，and to explore their relationship with gestational age and gestational week.

Methods

A total of 95 normal pregnant women（95 eyes）who visited the Department of Ophthalmology and Obstetrics of Chengdu Women and Children's Central Hospital from May 2022 to November 2023 were selected as the research subjects.Among them，the age ranged from 22 to 40 years old，with an average age of（29.0±3.43）years；the gestational age ranged from 8 to 40 weeks，with an average gestational age of（24.0±9.64）weeks.Three-dimensional optical coherence tomography was used to collect fundus color photographs centered on the optic disc and measure the retinal thickness of the macular area.The fundus image analysis software was used to quantify the retinal vascular diameter and retinal vascular tortuosity.The differences in retinal directions and partitions in different eyes，different directions，different gestational ages，and different gestational periods were compared.The measured data of retinal curvature，retinal vessel diameter and retinal thickness were in accordance with normal distribution and expressed as±s.The independent sample t test was used for comparison between groups，the paired t test was used for comparison between different eyes of the same pregnancy，and the one-way repeated measures analysis of variance was used for comparison between different positions and subareas.When the difference was statistically significant，further pairwise comparison was performed.

Results

48 women were aged 22 to＜30 years old and 47 were aged 30 to 40 years old in normal pregnancy.There were 19 women with gestational age＜14 weeks（early pregnancy），31 women with 14 to 27 weeks（mid-term pregnancy），and 45 women with≥28 weeks（late pregnancy）.There were no significant differences in the mean retinal arteriovenous tortuosity，mean retinal arteriovenous diameter，and retinal foveal thickness between the left and right eyes（t=1.561，0.487，0.962，0.497，0.978；P＞0.05）.The diameters of retinal arteries in different directions were（8.764±1.391）pixels，（9.414±1.481）pixels，（7.712±1.021）pixels and（7.422±1.244）pixels，respectively，and the differences were statistically significant（F=41.811，P＜0.05）.The diameters of retinal veins were（10.374±1.718）pixels，（10.925±1.997）pixels，（8.195±1.095）pixels and（7.891±1.114）pixels，respectively，and the differences were statistically significant（F=82.289，P＜0.05）.The retinal thickness of the fovea，the temporal，superior，nasal and inferior regions of the central area were（222.69±19.57）μm，（290.91±12.62）um，（305.01±13.51）μm，（301.58±15.44）μm and（301.58±12.77）μm，respectively；the retinal thickness of the temporal，superior，nasal and inferior regions of the paracentral area were（255.42±14.65）μm，（272.09±14.72）μm，（284.95±21.08）μm and（258.75±12.02）μm，respectively，and the differences were statistically significant（F=299.81，P＜0.05）.The mean retinal arterial curvature in the gestational age groups of 20 to 29 years and 30 to 40 years was（0.602±0.424）and（0.569±0.342）respectively；the mean retinal venous curvature was（0.359±0.283）and（0.341±0.208）respectively；the mean retinal arterial diameter was（8.347±0.767）pixels and（8.309±0.761）pixels respectively；the mean retinal venous diameter was（9.336±0.760）pixels and（9.376±0.879）pixels respectively；the foveal thickness was（221.42±19.57）μm and（224.00±19.69）μm，respectively.There were no statistically significant differences in the average retinal arteriovenous tortuosity，average retinal arteriovenous diameter，and retinal foveal thickness among different gestational age groups（t=0.407，0.361，0.243，-0.236，-0.641；P＞0.05）.In the early，middle and late pregnancy stages，the curvatures of the superior temporal artery，inferior temporal artery，superior nasal artery and inferior nasal artery were（0.517±0.533），（0.602±0.644），（0.528±0.721），（0.652±0.760），（0.641±0.684），（0.767±0.913），（0.689±0.908），（0.461±0.426），（0.597±1.019），（0.467±0.526），（0.464±0.463）and（0.577±0.731），respectively；the mean retinal artery tortuosity was（0.581±0.426），（0.542±0.306）and（0.617±0.418）；at different gestational stages，the curvatures of the superior temporal vein，inferior temporal vein，superior nasal vein and inferior nasal vein were（0.235±0.334），（0.416±0.573），（0.310±0.657），（0.248±0.314），（0.523±0.502），（0.494±0.951），（0.260±0.301），（0.299±0.285），（0.366±0.369），（0.266±0.244），（0.349±0.305）and（0.265±0.238），respectively；the average curvatures of the retinal veins were（0.253±0.168），（0.399±0.209）and（0.359±0.289），respectively.The curvature of the superior temporal vein，inferior temporal vein，superior nasal vein，and inferior nasal vein of the retina showed a trend of increasing in the second trimester compared with the first trimester.The difference in the average curvature of the retinal veins between the first and second trimester groups was statistically significant（t=-2.577，P＜0.05）.At different stages of pregnancy，the calibers of the superior temporal artery，inferior temporal artery，superior nasal artery，and inferior nasal artery were（8.303±1.022）pixels，（9.100±1.602）pixels，（8.727±1.336）pixels，（9.166±1.502）pixels，（9.769±1.318）pixels，（9.274±1.563）pixels，（7.977±0.858）pixels，（7.733±1.207）pixels，（7.586±0.940）pixels，（7.077±0.812）pixels，（7.735±1.522）pixels，and（7.353±1.154）pixels，respectively；the mean retinal artery diameters were（8.131±0.593）pixels，（8.585±0.849）pixels，and（8.235±0.725）pixels，respectively；the diameters of the superior temporal vein，inferior temporal vein，superior nasal vein and inferior nasal vein of the retina were（10.388±1.675）pixels，（10.834±1.798）pixels，（10.051±1.643）pixels，（10.964±1.982）pixels，（10.787±2.032）pixels，（11.003±2.019）pixels，（8.047±1.342）pixels，（8.295±0.990）pixels，（8.189±1.068）pixels，（7.964±0.865）pixels，（7.544±1.249）pixels，and（8.090±1.077）pixels，respectively；the average diameters of the retinal veins were（9.341±0.933）pixels，（9.397±0.869）pixels and（9.333±0.745）pixels.The diameters of the superior temporal artery，inferior temporal artery，superior nasal artery and inferior nasal artery in the second trimester increased compared with those in the first trimester.The average diameters of the retinal arteries in the first and second trimesters were statistically significant（t=-2.041，P＜0.05）.At different stages of pregnancy，the foveal thickness of the retina was（222.11±18.62）μm，（223.55±20.43）μm and（222.36±19.77）μm，respectively；the average retinal thickness of the central area of the retina was（299.84±12.96）μm，（300.89±13.70）μm，（298.96±11.25）μm，respectively；the average retinal thickness of the paracentral area of the retina was（266.75±14.18）μm，（267.39±14.56）μm，（268.53±10.48）μm，respectively.There were no significant differences in the foveal thickness，the average retinal thickness in the central area，and the average retinal thickness in the paracentral area among the groups at different gestational stages（t=-0.250，-0.047，0.255，-0.269，0.289，0.673，-0.152，-0.607，-0.399；P＞0.05）.

Conclusions

The retinal microcirculation and morphological parameters during normal pregnancy are related to the gestational age.The changes in the retinal microcirculation and morphology during pregnancy can reflect retinal function，providing evidence for early retinal diseases.

Key words: Normal pregnancy, Retinal blood vessels, Retinal thickness