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URINARY TRACT INFECTIONS IN PREGNANCY

KY Loh MMed(FamMed UKM) 
N SivalingamFRCOG
Dr Loh Keng Yin is from the Department of Family Medicine, Dato’ Prof Sivalingam Nalliah is from the Department of Obstetrics & Gynaecology, International Medical University, Seremban, Malaysia

Address for correspondence: Associate Professor Dr Loh Keng Yin, International Medical University, Jalan Rasah, 70300 Seremban, Malaysia. Tel: 06-7677798, Fax: 06-7677709, Email: kengyin_loh@imu.edu.my

Conflict of interest: None

INTRODUCTION

Urinary tract infections (UTI) remain a leading cause of morbidity and healthcare expenditure in all age groups.^1,2 UTI account for about 10% of primary care consultations by pregnant women and it was reported that up to 15% of women will have one episode of UTI at some time during their life.¹  The incidence of UTI reported among pregnant mothers is about 8%.^1,2  Anatomically UTI can be classified into lower urinary tract infection involving the bladder and urethra and upper urinary tract infection involving the kidney and pelvis ureter. The majority of the UTI occur due to ascending infection.^1,2

PHYSIOLOGICAL CHANGES OF PREGNANCY AND ITS ASSOCIATION WITH URINARY TRACT INFECTIONS

Pregnancy increases the risk of UTI. At around 6th week of pregnancy, due to the physiological changes of pregnancy the ureters begin to dilate. This is also known as "hydronephrosis of pregnancy", which peaks at 22-26 weeks and continues to persist until delivery.¹ Both progesterone and estrogens levels increase during pregnancy and these will lead to decreased ureteral and bladder tone. Increased plasma volume during pregnancy leads to decrease urine concentration and increased bladder volume.¹ The combination of all these factors lead to urinary stasis and uretero-vesical reflux. Glycosuria in pregnancy is also another well-known factor which predisposes mothers to UTI.

TYPES OF URINARY TRACT INFECTIONS IN PREGNANCY

There are three major types of UTI in pregnancy. They are asymptomatic bacteriuria, acute cystitis and acute pyelonephritis. The clinical presentations of these conditions vary.

Asymptomatic bacteriuria is defined as a finding of more than 10⁵ colony-forming units per mL of urine in a clinically asymptomatic person.^1,2 This condition may be present even before the mother gets pregnant. There are reports that 1.2 to 5 % of young girls will demonstrate asymptomatic bacteriuria at some time before puberty.^3,5 The prevalence of asymptomatic bacteriuria in pregnancy is about 10%. Lower serum interleukin-6 levels and serum antibody responses to E. coli antigens which occurs in pregnancy has been associated with increased incidence of asymptomatic bacteriuria in pregnancy.⁵ Neonatal complications which are associated with asymptomatic bacteriuria include intrauterine growth restriction, low birth weight and pre-term premature rupture of membrane.^3,5,7 Maternal complications which are associated with asymptomatic bacteriuria are hypertension, pre-eclampsia and maternal anemia.¹³ Without treatment, this condition leads to symptomatic cystitis in about 30% of pregnant mothers of whom about 50% will eventually develop acute pyelonephritis.^3,5,7 (Table 1 )

Table 1. Maternal and foetal complications of asymptomatic bacteriuria in pregnancy.^9,10

Maternal complications	Foetal complications
Hypertension Pre-eclampsia Anaemia Chorioamnionitis Symptomatic acute cystitis Acute pyelonephritis	Intrauterine growth retardation Intrauterine death Low birth weight Prematurity