New birth weight nomograms for twin gestation on the basis of accurate gestational age.

OBJECTIVE

Our purpose was to establish new nomograms for the birth weight of twins on the basis of accurate methods to validate gestational age.

STUDY

DESIGN

The medical records of 1632 consecutive twin gestations delivered between 1984 and 1996 were reviewed. Only pregnancies induced by ovulation induction techniques or that were measured ultrasonographically for crown-rump length during the first trimester were included. Excluded were those whose fetuses (one or both) were stillborn, or if the mother smoked, had a significant chronic illness, or was prescribed any regular medications. The study comprised 520 twin pregnancies at 28 to 41 gestational weeks at delivery.

RESULTS

The median and 10th and 90th percentile birth weight curves were calculated for the studied twins and plotted against previously reported singleton nomograms. Fetuses of twin pregnancies were found to be growth restricted in comparison with previously reported singletons throughout the third trimester. This trend became more evident after the thirty-fourth to thirty-sixth weeks.

CONCLUSIONS

We recommend these novel birth weight nomograms for clinical use in the management of twin pregnancies.