Waller D K, Spears W D, Gu Y, Cunningham G C
The University of Texas, Houston Health Science Center, School of Public Health, 77225, USA.
Paediatr Perinat Epidemiol. 2000 Jul;14(3):263-7. doi: 10.1046/j.1365-3016.2000.00275.x.
The goal of this investigation was to determine whether women who did not report preferred numbers for their last menstrual period (LMP) may be a group of women who are particularly careful in keeping track of their menstrual cycles and therefore have more accurate LMP dating--based on a comparison with ultrasound examinations. We also sought to estimate the frequency with which preferred numbers are reported in different sources of data and for different subgroups of women. First, we examined the 1987 California birth certificates in which LMP was collected at the time of birth (n = 504853). We also examined the records of 43880 women participating in the California Alpha-fetoprotein (AFP) Screening Program between 1986 and 1987, for whom gestational ages based on both early ultrasound examination and LMP were collected before 20 weeks of gestation. In the 1987 California birth certificates, seven numbers--1, 5, 10, 15, 20, 25 and 28--were recorded more frequently than expected. An estimated 12.9% of these records had preferred numbers. The most frequently recorded number was 15, occurring 2.5 times more often than expected (P < 0.01). In the data of the AFP Screening Program, the same seven numbers were preferred, and approximately 7.9% of records were affected by number preference. Comparisons with measurements of gestational age based on ultrasound demonstrated that LMP-based gestational ages in which non-preferred numbers are reported for the LMP are slightly more accurate than those in which preferred numbers are reported (P < 0.01). In most cases, number preference appears to introduce small errors into measurements of gestational age, probably as a result of rounding. Thus, the effect of number preference may be primarily of interest to research studies in which small errors in the measurement of gestational age will have a significant impact on findings.
本研究的目的是确定那些未报告末次月经日期（LMP）的偏好数字的女性，是否属于特别留意记录月经周期、因此末次月经日期估算更为准确的女性群体——这是通过与超声检查结果进行比较得出的结论。我们还试图估算在不同数据来源以及不同女性亚组中，报告偏好数字的频率。首先，我们查阅了1987年加利福尼亚州的出生证明，其中在出生时收集了末次月经日期（n = 504853）。我们还查阅了1986年至1987年间参与加利福尼亚州甲胎蛋白（AFP）筛查项目的43880名女性的记录，对于这些女性，在妊娠20周之前收集了基于早期超声检查和末次月经日期的孕周数据。在1987年加利福尼亚州的出生证明中，七个数字——1、5、10、15、20、25和28——的记录频率高于预期。估计这些记录中有12.9%有偏好数字。记录最频繁的数字是15，出现频率比预期高2.5倍（P < 0.01）。在AFP筛查项目的数据中，同样是这七个数字更受青睐，约7.9%的记录受到数字偏好的影响。与基于超声测量的孕周进行比较表明，报告末次月经日期时使用非偏好数字的基于末次月经日期的孕周，比报告偏好数字的孕周略为准确（P < 0.01）。在大多数情况下，数字偏好似乎会给孕周测量带来小误差，可能是四舍五入的结果。因此，数字偏好的影响可能主要在孕周测量的小误差会对研究结果产生重大影响的研究中受到关注。
