Development of fetal growth charts in twins stratified by chorionicity and mode of conception: a retrospective cohort study in China

Comparison of singleton and twin birth weight reference percentile curves by gestational age and sex in extremely preterm infants: a population-based study

BACKGROUND

With the increasing survival rate of smaller newborns and twins, previous growth curves may not accurately assess the growth of extremely preterm infants (EPIs). Our study aimed to establish birth weight percentile curves for singletons and twins in EPIs from China and the USA and compare the differences between them.

METHODS

In China, EPIs were from 31 provinces, from 2010 to 2021. The collected information was sex, gestational age, birth weight, singletons and twins. We used the generalised additive models for location scale and shape method to construct the birth weight percentile curves by gestational age and sex for EPIs. The National Vital Statistics System database from 2016 to 2021 was also analysed. We compared the differences between the 50th birth weight percentile curves of the two databases.

RESULTS

We identified 8768 neonates in China (5536 singletons and 3232 twins) and 121 933 neonates in the USA (97 329 singletons and 24 604 twins). We established the 3rd, 10th, 25th, 50th, 75th, 90th and 97th birth weight reference curves for China and the USA. The results showed that males had higher birth weights than females. In China, for the same gestational age and sex, birth weights in singletons and twins were found to be similar, though singleton males born in China had slightly higher birth weights than male twins. In the USA, birth weights were also similar for females and males, with the same gestational age in singletons and twins.

CONCLUSION

We established birth weight reference percentile curves by gestational age and sex for singletons and twins among EPIs in China and the USA.

Fetal growth trajectories of small/large for gestational age infants in twin pregnancies

BACKGROUND

Birthweight is the most common and accessible parameter in assessing neonatal perinatal outcomes and in evaluating the intrauterine environment globally. Infants born too large or too small not only may alter the maternal mode of delivery but also may face other long-term disorders, such as metabolic diseases and neurodevelopmental delay. Studies have revealed different growth profiles of large-for-gestational-age and small-for-gestational-age fetuses in singleton pregnancies. However, currently, no research is focused on the growth trajectories of these infants during twin pregnancies, even though they are at a much higher risk of being small for gestational age.

OBJECTIVE

This study aimed to explore fetal growth trajectories of large-for-gestational-age and small-for-gestational-age infants in twin pregnancies to provide strategies for fetal growth management.

STUDY DESIGN

This was a case-control study of all noncomplicated twin pregnancies delivered after 36 weeks of gestation at the Peking University First Hospital between 2012 and 2021. Ultrasound data were recorded every 2 to 4 weeks until delivery. All the infants were divided into large-for-gestational-age, small-for-gestational-age, and appropriate-for-gestational-age groups. Longitudinal fetal growth (estimated fetal weight, abdominal circumference, etc.) was compared among the 3 groups using a linear mixed model, and other maternal and neonatal perinatal outcomes were compared. Receiver operating characteristic curves were used to explore optimal biometric parameters and gestational weeks for predicting small-for-gestational-age infants.

RESULTS

Here, 797 pregnant patients with 1494 infants were recruited, with 59 small-for-gestational-age infants, 1335 appropriate-for-gestational-age infants, and 200 large-for-gestational-age infants. The mean birthweights were 1985.34±28.34 g in small-for-gestational-age infants, 2662.08±6.60 g in appropriate-for-gestational-age infants, and 3231.24±11.04 g in large-for-gestational-age infants. The estimated fetal weight of the 3 groups differed from each other from week 26, with the small-for-gestational-age fetuses weighing 51.946 g less and the large-for-gestational-age fetuses weighing 35.233 g more than the appropriate-for-gestational-age fetuses. This difference increased with gestation; at 39 weeks, the small-for-gestational-age fetuses weighed 707.438 g less and the large-for-gestational-age fetuses weighed 614.182 g more than the appropriate-for-gestational-age fetuses (all P<.05). The small-for-gestational-age group had a significantly higher rate of hospitalization (89.9 %) and jaundice (40.7 %) than the appropriate-for-gestational-age group, whereas the hospitalization rate in the large-for-gestational-age group was significantly lower than the appropriate-for-gestational-age group (7.5% and 2.5%; all P<.05). The fetal weight of the small-for-gestational-age infants with adverse outcomes remained near the 10th percentile of the reference and fell below the 3rd percentile at 34 weeks of gestation. The estimated fetal weight after 30 weeks of gestation had a satisfactory diagnostic value in predicting small-for-gestational-age infants. At 30, 32, 34, and 36 weeks of gestation, the areas under the curve were 0.829, 0.840, 0.929, and 0.889 respectively.

CONCLUSION

The growth patterns of small-for-gestational-age, appropriate-for-gestational-age, and large-for-gestational-age twin fetuses diverged from 26 weeks of gestation and continued to increase until delivery; therefore, closer monitoring is suggested from 26 weeks of gestation for those carrying small fetuses.