Background: Many epidemiological studies have shown that lower urinary tract symptoms (LUTS) are common during the first pregnancy. Both prevalence and severity of LUTS seem to increase through out pregnancy. It also compromised daily life of pregnant women. Both anatomical change and hormonal change during pregnancy can disrupt the normal urinary tract function.
Objective: The aim of the present study is to identify the effect of pregnancy in different trimesters of pregnancy on urinary function of Thai nulliparous women by using free uroflowmetry.
Material and Method: A prospective study of 111 Thai nulliparous pregnant women at 8-12, 24-28 and 32-38 gestational weeks. They attended the antenatal clinic in Thammasat Hospital. All women were interviewed about their urinary symptoms such as hesitancy, frequency, nocturia, stress incontinence, urge incontinence and difficulty in passing urine. The severity of each symptom was clarified as none, mild, moderate and severe. Free uroflowmetry was performed using a special-setting
toilet in the clinic. Maximum flow rate (Qmax), average flow rate (Qavg), voided volume (VV) and residual urine volume were measured.
Results: Mean age of 111 women was 26.6+5.4 years and the mean body weight was 52.4+9.4 kilograms. The average gestational age was 8.6+1.9 weeks at first visit, 26.1+1.3 weeks at second visit and 34.1+1.6 weeks at last visit. The symptom of urinary frequency and nocturia increased throughout pregnancy. Only two women at 24-28 weeks and one woman at 34-38 weeks reported moderate to severe stress incontinence. No women had moderate to severe urge incontinence. Maximum and average flow rates slightly increased toward the end of pregnancy. But voided volume was slightly decreased in the second and third visits. Residual urine of less than 50 ml was found in all women and all periods.
Conclusion: Urinary frequency and nocturia were common in Thai nulliparous pregnancy. Most of them did not complain
of stress nor urge incontinence. Maximum and average flow rate seem to increase consistently while gestational age increase and average voided volume were reduced in late pregnancy.

Keywords: Pregnancy, Uroflowmetry