Variation of force applied during external cephalic version with different patients' characteristic and outcome of version.
BACKGROUND
To compare the degree of force applied during external cephalic version, between different patients' characteristic and outcomes of version.


METHODS
It is a prospective observational study in a cohort of patients undergoing external cephalic version at or above 36 weeks of gestation. During external cephalic version, the operator wore a pair of pressure-sensing gloves which had ultra-thin piezo-resistive pressure sensors positioned on the palmer surface. Readings from each of the sensors were recorded in real time throughout each version attempt and analyzed by a computer program. The pressure exerted on individual sensors over time, the pressure-time integral (PTI; mmHg s), was calculated for each sensor from the start to the end of each version attempted. The degree of force applied for each attempt (PTI-A) was represented by the sum of pressure-time integrals across all sensors. PTI-A was analyzed in relation to different patients' characteristics and outcome of version.


RESULTS
Ninety-two patients were recruited, 73% of whom had a successful external cephalic version. The median PTI-A of the successful attempt in women who completed version after 1 and 2 attempts were 17,180 and 17,736 mmHg s, respectively. They were significantly lower than that of the women who required 3 or more attempts for a successful version (32,351 mmHg s), as well as the highest PTI-A among all attempts received by women who finally had a failed version (31,638 mmHg s) (p <0.05, Kruskal-Wallis Test and Dunn test). Within the same subject, there was no difference in PTI-A between the successful attempt and the preceding failed attempt, suggesting that the failure may not be due to insufficient force but rather to inefficient application of the force. Uterine tone was found to be the only clinical variable that was significantly associated with the degree of applied force during a version (p < 0.05). A tenser uterus was associated with a stronger applied force.


CONCLUSIONS
The degree of force required for a successful version is highly variable, being lowest when version can be completed within 2 attempts, but doubled when 3 or more attempts are required. Failure of version is usually not due to inadequate force but inefficient application of force. Uterine tone is significantly related to the degree of applied force, with stronger force being exerted when the uterus is tense.
Department of Obstetrics and Gynaecology, Prince of Wales Hospital, Chinese University of Hong Kong, Hong Kong. tyleung@cuhk.edu.hk
Tak Yeung
TY
Leung
Daljit Singh
DS
Sahota
Lin Wai
LW
Chan
Wing Yee
WY
Fok
Lai Wa
LW
Law
Tze Kin
TK
Lau
D000293:Adolescent; D000328:Adult; D001946:Breech Presentation; D005260:Female; D006801:Humans; D011247:Pregnancy; D011256:Pregnancy Outcome; D011312:Pressure; D011446:Prospective Studies; D018709:Statistics, Nonparametric; D014710:Version, Fetal / Q000379:methods*