Nomogram of Cervical Length at Mid-trimester in Normal Thai Pregnant Women
Ekachai Kovavisarach MD*,**, Wipawan Sukontaman MD**
Affiliation : * Department of Obstetrics and Gynecology, Rajavithi Hospital,College of Medicine, Rangsit University, Bangkok, Thailand ** Department of Obstetrics and Gynecology, Rajavithi Hospital, Bangkok, Thailand
Background : As cervical length decreases in the second trimester, the risk of spontaneous preterm birth increases, especially
when effacement occurs early in the second trimester, and it is often detected on ultrasound examination before it can be
identified by physical examination. To date, only two Thai nomograms of transvaginal cervical length have been reported.
Objective : To establish a new Thai nomogram as a reference for evaluation of transvaginal cervical length in a tertiary Thai
hospital in Bangkok (Rajavithi Hospital: RH) during gestational age (GA) 16 to 24 weeks.
Material and Method: This research was approved by the ethics committee of RH (No. 055/2558). A total of 286 normal Thai
pregnant women who attended the antenatal clinic (ANC) at RH between May 1, 2015 and November 30, 2015 were included.
All were cases of singleton gestation with no medical or obstetric complications and no fetal congenital anomalies; and all had
GA confirmed by Crown Rump Length (CRL) before GA of 14 weeks. Cervical length measurement was performed by a single
operator using transvaginal ultrasonography (7.5 mHz Voluson E8) during GA of 16 to 24 weeks. The subjects attended
follow-up sessions in the antenatal care clinic until delivery.
Results : One hundred and ninety-six cervical measurements were analysed (90 patients were excluded: 7 because of preterm
labor, and 83 because they were lost to follow-up). The mean maternal age was 29.49+6.5 years, and the most common
pregnancy status was nullipara (48.3%). The mean CL of nulliparous, multiparous and overall women were 37.87, 39.46
and 38.70 mm respectively. The CL values were constant during the examined GA.
Conclusion : The mean cervical length of normal Thai pregnant women between GA of 16 to 24 weeks examined transvaginally
was 38.70 mm.
Keywords : Cervical length (CL), Transvaginal ultrasonography
