Reliability of sonographic fetal weight estimation in triplet pregnancies: a retrospective cohort study

PURPOSE

To review our experience in ultrasound fetal weight estimation in our large population of triplet pregnancies.

METHODS

Ninety-seven triplet pregnancies were retrospectively included between January 2003 and January 2017. Sonographic fetal weight estimation using Hadlock's and Schild's formulas was compared to actual birth weight in a tertiary-care center in Vienna, Austria. Statistical analyses were performed using a stepwise linear regression model and crosstabs.

RESULTS

The median discrepancy between the sonographically estimated fetal weight by Hadlock's formula and the actual birth weight was 106 g (IQR 56-190). The percentage error and its standard deviation were - 2.5 ± 12.1%, and the median percentage error was - 3.6%. Concerning the use of Hadlock's formula, estimated fetal weight was the most important factor predictive of actual birth weight with an estimate of 0.920 (p < 0.001). Female neonates had been overestimated by a mean of 50.473 g per fetus. The sonographic prediction of small-for-gestational-age neonates was significantly reliable (p < 0.001), with positive and negative predictive values ranging from 81.3 to 100.0%. Similar results were obtained for Schild's formula.

CONCLUSION

Even if sonographically estimated fetal weight in triplet pregnancies has a high overall accuracy of fetal weight estimation, there are some limitations in prediction of intrauterine growth restrictions, especially in female fetuses.

Cervical length dynamics in triplet pregnancies: a retrospective cohort study

Purpose

To review our experience with a screening program that included sequential cervical length measurements in our large population of triplet pregnancies.

Methods

Seventy-eight triplet pregnancies were retrospectively included. Cervical length measurements were performed by transvaginal ultrasound in 2-week intervals from week 16 + 0 onwards in a tertiary-care center in Vienna. The main outcome measurement was preterm delivery prior to 32 + 0 weeks of gestation. Statistical analyses were performed using paired and unpaired t tests and a stepwise linear regression model.

Results

There were 26 cases of preterm delivery (33.3%). Women with preterm delivery revealed significant cervical length shortening from week 22 + 0 (median 33 mm, interquartile range, IQR 17–39) to 24 + 0 (median 21 mm, IQR 7–30; p = 0.005). This was not observed in women without preterm delivery. From week 22 + 0 onwards, both groups showed further significant 2-week differences in cervical length (p < 0.05). Univariate analysis of cervical length in weeks 20 + 0, 22 + 0, and 24 + 0 as well as cervical length dynamics from 22 + 0 to 24 + 0 predicted preterm delivery.

Conclusions

In triplet pregnancies, a decrease in cervical length seems physiological from week 22 + 0 onwards. A sharp decrease in cervical length from the 22 + 0 to the 24 + 0 week as well as the smaller cervical length in weeks 20 + 0, 22 + 0, and 24 + 0 increase the risk of preterm delivery.