We read with great interest the article on the potential effect of progesterone therapy on the fetal nuchal translucency (NT) thickness during the first trimester. The authors advocate that exogenous progesterone increases NT.
However, we feel that this assumption is not supported by their data. First, the authors show only a very mild NT increase of only 0.04 multiples of the median (MoM) which, although minimally statistically significant ( P < .05), is clearly clinically not relevant. In the low-risk group, the difference in the NT was even lower (0.02 MoM). Second, comparisons by week of gestation showed only NT differences at 11 weeks ( P < .02), but not at 12 and 13 weeks of gestation. This is important because most of the screenings are now performed at 12-13 weeks of gestation to check the early fetal anatomy also. Third, their results are based on a mixture of different progestogens that were administered by different routes and at different doses, which makes comparisons difficult to interpret. Fourth, most of the progesterone-treated pregnancies (77.7%) had a threatened miscarriage; to rule out a potential influence of such bleedings on fetal hemodynamics and NT, the authors should also have performed a subanalysis that omitted this group or compared it to another group of untreated threatened miscarriage.
There is extensive evidence among studies in pregnancies that are achieved by assisted conceptions that demonstrate, indirectly, the lack of influence of progesterone on NT. Our own data show the lack of even a trend of any effect of micronized natural progesterone on NT ( P = not significant), despite the inclusion of a subgroup with a maximum dose of natural progesterone ( Table ).
| Variable | Average daily dose of vaginal micronized natural progesterone until week 12 of gestation | n | Nuchal translucency, multiples of the median (95% confidence interval) |
|---|---|---|---|
| Natural conception | 0 | 2011 | 0.98 (0.96–0.99) |
| Intrauterine insemination | 200 mg a | 350 | 0.97 (0.94–1.0) |
| In vitro fertilization/intracytoplasmic sperm injection with own oocytes | 400 mg b | 1086 | 0.98 (0.96–1.0) |
| In vitro fertilization/intracytoplasmic sperm injection with ovum donation | 800 mg b | 606 | 0.96 (0.94–0.98) |
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