Objectives: The effect of exogenous progesterone on fetal nuchal translucency (NT) has been proposed recently. In this study, we aimed to compare the thickness of NT of patients receiving and not receiving progesterone for threatened miscarriage.

Material and methods: This study was designed as a retrospective comparative study. Ninety five women treated with progesterone constituted the study group whereas 97 women who were not treated with progesterone constituted the control group. An ultrasonographic examination was performed on all of the women to measure NT. All patients were treated with oral micronized progesterone in the study group. The main parameters recorded for each woman were; age, body mass index (BMI), obstetrical characteristics, and gestational age at first examination, treatment duration of progesterone therapy, and results of combined and triple tests.

Results: A total of 192 pregnant women with threatened miscarriage were included in this study. The mean NT thickness was statistically significantly higher in the study group (p < 0.001), and mean serum level of human chorionic gonadotropin (hCG) was also higher in this group (p < 0.05). There was no statistically significant difference between groups in terms of age, BMI, and gestational age at first examination. ROC curve analysis demonstrated that only increased NT (area under the curve: 0.634, p = 0.005, 95% CI: 0.541–0.727) was a discriminative factor for women receiving progesterone for threatened miscarriage. Also there was a positive correlation between NT and treatment duration (r = 0.269; p < 0.001).

Conclusions: We think that oral progesterone therapy may increase NT depending on treatment duration without causing abnormal prenatal screening test results.