Tape measurement of symphysis-fundal height in twin pregnancies.

We hypothesized that tape measurement of symphysis-fundal height could be useful in detecting multiple pregnancies, and in such cases in predicting preterm labour and identifying small-for-gestational-age (SGA) fetuses. Although mean fundal height is substantially greater in twin than singleton pregnancies, the value of the technique to detect multiple pregnancies may be limited because combined birth-weight is less and the frequency of SGA fetuses is greater in undiagnosed than in diagnosed twin pregnancies. We found no evidence that the measured fundal height is greater in pregnancies going on to preterm delivery, and we suggest that the commonly accepted theory that the high rate of preterm labour in twin pregnancies results simply from uterine overdistension be reappraised. Nevertheless, fundal height measurement was of value in identifying pregnancies in which both babies were SGA and is therefore recommended as a simple, inexpensive and non-invasive technique.