Purpose: to compare cervical length measurements in twin pregnancies obtained by transvaginal ultrasound examination in the recumbent and standing positions. Methods: fifty twin pregnancies underwent transvaginal ultrasound examinations to measure the cervical length with the women in recumbent and standing positions. The study was carried out between May 1999 and December 2000. The scans were repeated every 4 weeks and the total number of evaluations was 136. Two groups were analyzed: one included only the first ultrasound examinations carried out in each woman and the second group included all evaluations. Results: in the first group, cervical length measurements in the standing and recumbent positions correlated inversely with the gestational age (recumbent: r=-0.60; p<0.001; standing: r=-0.46; p=0.008). The mean measure in the recumbent position was 35.2 mm (SD=9.9 mm) and 33.4 mm (SD=9.5 mm) in the standing position. When the difference between the measure obtained in the standing and recumbent positions was expressed as percentage of the measure in the recumbent position, there was no significant association with gestational age (p=0.07). When all evaluations were considered, there was a significant association between cervical length in the recumbent and standing positions (r=0.79; p<0.001). The measures in recumbent and standing positions were inversely correlated with gestational age (recumbent: p<0.0001; standing: p<0.0001). The mean cervical length in the recumbent position was 33.5 mm (SD=10.8 mm) and 31.8 mm (SD=9.6 mm) in the standing position. There was no significant association between cervical length difference expressed as percentage of the measure in the recumbent position and gestation. Conclusion: cervical length measure obtained with the patients in the recumbent and standing positions provided similar information.
Preterm delivery; Twin pregnancy; Uterine cervix; Normal pregnancy
