Early fetal growth in progesterone-treated IVF pregnancies

The aim of this study was to compare fetal growth in the first and second trimesters of pregnancy and final birth weights between two groups of women: (a) spontaneous conceptions with reliable menstrual dates and (b) IVF pregnancies on progesterone supplementation during the first trimester.

We included in the study 73 singleton IVF pregnancies and 138 singleton spontaneous pregnancies. Exclusion criteria were: medications or presence of medical conditions affecting fetal growth. Fetal crown-rump length (CRL) at 10 + 1 to 13 + 6 weeks of gestation, and head circumference (HC), biparietal diameter (BPD), abdominal circumference (AC) and femur length (FL) at 18-24 weeks, were measured prospectively. The birth weights of the babies born were collected and compared. Independent sample t test was applied for comparing quantitative variables with normal distribution, and Wilcoxon-Mann-Whitney test was used for comparison of quantitative variables without normal distribution.

IVF fetuses on progesterone supplementation had larger CRL measurements when compared to their counterparts from spontaneous pregnancies (p value = 0.045). Similarly, in the second trimester, the BPD was significantly larger but HC, AC and FL, although larger, did not reach statistical significance. The birthweights of babies between the two groups showed no statistically significant difference, although some IVF babies were born prematurely.

Enhanced fetal growth during the first trimester has been observed with progesterone supplementation in IVF pregnancies. Aspects of enhanced fetal growth were observed in the second trimester but not at birth. The effect of progesterone supplementation on fetal growth needs further investigation.