Objective To explore the association between dynamic indexes of maternal progesterone in early pregnancy and the average level and growth rate of fetal head circumference(HC)in mid-and late pregnancy.Methods This study adopted a retrospective cohort design and included 255 singleton pregnant women in the maternal and infant cohort of The First Affiliated Hospital of Xi'an Jiaotong University from January 2015 to December 2024.The progesterone levels of their early venous blood were detected and divided into two groups of progesterone trajectories,namely,fluctuating type and increasing type,by morphology.The dynamic indicators of progesterone in early pregnancy were constructed:cumulative dynamic deviation index in the first trimester(CDDI-P1T),gestational age at progesterone peak(GA-PP),and maximal relative progesterone decline in the first trimester(MRD-P1T).The average head circumference level and linear growth rate of the fetuses in the middle and late pregnancy were calculated.Generalized linear regression(GLM)was used to analyze the linear association between progesterone dynamic indicators and head circumference development.The key gestational weeks of progesterone affecting fetal head development were explored by linear regression of gestational weeks.Ordinary least squares(OLS)regression and restricted cubic spline(RCS)plots were used to draw the nonlinear association between progesterone dynamic indicators and head circumference.Results Among the 255 pregnant women included,92.5％of the progesterone trajectories in early pregnancy were fluctuating,and 7.5％were increasing.The growth rates of the increasing progesterone trajectory group were higher in the second and third trimesters than in the fluctuating group,but the differences were not statistically significant(all P＞0.05).GLM analysis showed that for every 1 unit increase in CDDI-P1T,the head circumference in the middle and late pregnancy increased significantly by 1.574 cm and 1.193 cm(Z=3.714,2.885,P＜0.01).The delay of GA-PP was negatively correlated with the head circumference in the middle pregnancy(β=-0.190 cm,95％CI:-0.339--0.041,P=0.010)but positively correlated with the head circumference growth rate in the late pregnancy(β=0.022 cm/week,95％CI:0.003-0.041,P=0.025).A 10％decrease in the decline of CDDI-P1T increased the head circumference in the middle pregnancy by 0.200 cm(95％CI:0.016-0.384,P=0.033),and a 100％decrease in the decline increased the head circumference growth rate in the late pregnancy by 0.201 cm/week(95％CI:0.002-0.399,P=0.048).The analysis of the key time window showed that for every 20 nmol/L increase in progesterone during 9.5-13 weeks of pregnancy,the mid-term head circumference increased by 0.035-0.166 cm(Z=2.452-3.517,allP＜0.05),and the late-term head circumference increased by 0.767 cm during 9-13 weeks of pregnancy(Z=2.452-3.517,all P＜0.05).When progesterone increased during 9.5-10.5 weeks of pregnancy,the growth rate of mid-term head circumference increased by 0.013-0.023 cm/week(Z=2.074-2.243,all P＜0.01).When progesterone increased during 8.5-10.5 weeks of pregnancy,the growth rate of late-term head circumference increased by 0.010-0.026 cm/week(Z=2.061-3.137,all P＜0.05).Conclusion Progesterone dynamic index is a new sensitive tool for evaluating fetal head circumference development.There is a stage-specific window period for progesterone regulation.9.5-13 weeks of pregnancy is the critical period for progesterone to affect head circumference growth,and 9.5-10.5 weeks of pregnancy is the core window for regulating the growth rate of head circumference.Therefore,it is necessary to combine progesterone dynamic index and time window for individualized intervention to promote the transformation of prenatal care from pregnancy maintenance to eugenics intervention.

Objective To explore the association between dynamic indexes of maternal progesterone in early pregnancy and the average level and growth rate of fetal head circumference(HC)in mid-and late pregnancy.Methods This study adopted a retrospective cohort design and included 255 singleton pregnant women in the maternal and infant cohort of The First Affiliated Hospital of Xi'an Jiaotong University from January 2015 to December 2024.The progesterone levels of their early venous blood were detected and divided into two groups of progesterone trajectories,namely,fluctuating type and increasing type,by morphology.The dynamic indicators of progesterone in early pregnancy were constructed:cumulative dynamic deviation index in the first trimester(CDDI-P1T),gestational age at progesterone peak(GA-PP),and maximal relative progesterone decline in the first trimester(MRD-P1T).The average head circumference level and linear growth rate of the fetuses in the middle and late pregnancy were calculated.Generalized linear regression(GLM)was used to analyze the linear association between progesterone dynamic indicators and head circumference development.The key gestational weeks of progesterone affecting fetal head development were explored by linear regression of gestational weeks.Ordinary least squares(OLS)regression and restricted cubic spline(RCS)plots were used to draw the nonlinear association between progesterone dynamic indicators and head circumference.Results Among the 255 pregnant women included,92.5％of the progesterone trajectories in early pregnancy were fluctuating,and 7.5％were increasing.The growth rates of the increasing progesterone trajectory group were higher in the second and third trimesters than in the fluctuating group,but the differences were not statistically significant(all P＞0.05).GLM analysis showed that for every 1 unit increase in CDDI-P1T,the head circumference in the middle and late pregnancy increased significantly by 1.574 cm and 1.193 cm(Z=3.714,2.885,P＜0.01).The delay of GA-PP was negatively correlated with the head circumference in the middle pregnancy(β=-0.190 cm,95％CI:-0.339--0.041,P=0.010)but positively correlated with the head circumference growth rate in the late pregnancy(β=0.022 cm/week,95％CI:0.003-0.041,P=0.025).A 10％decrease in the decline of CDDI-P1T increased the head circumference in the middle pregnancy by 0.200 cm(95％CI:0.016-0.384,P=0.033),and a 100％decrease in the decline increased the head circumference growth rate in the late pregnancy by 0.201 cm/week(95％CI:0.002-0.399,P=0.048).The analysis of the key time window showed that for every 20 nmol/L increase in progesterone during 9.5-13 weeks of pregnancy,the mid-term head circumference increased by 0.035-0.166 cm(Z=2.452-3.517,allP＜0.05),and the late-term head circumference increased by 0.767 cm during 9-13 weeks of pregnancy(Z=2.452-3.517,all P＜0.05).When progesterone increased during 9.5-10.5 weeks of pregnancy,the growth rate of mid-term head circumference increased by 0.013-0.023 cm/week(Z=2.074-2.243,all P＜0.01).When progesterone increased during 8.5-10.5 weeks of pregnancy,the growth rate of late-term head circumference increased by 0.010-0.026 cm/week(Z=2.061-3.137,all P＜0.05).Conclusion Progesterone dynamic index is a new sensitive tool for evaluating fetal head circumference development.There is a stage-specific window period for progesterone regulation.9.5-13 weeks of pregnancy is the critical period for progesterone to affect head circumference growth,and 9.5-10.5 weeks of pregnancy is the core window for regulating the growth rate of head circumference.Therefore,it is necessary to combine progesterone dynamic index and time window for individualized intervention to promote the transformation of prenatal care from pregnancy maintenance to eugenics intervention.