Subfertility is a prolonged delay in achieving clinical pregnancy despite unprotected sexual intercourse, which can be a sign of infertility – the inability to conceive naturally. Globally, five to 15 per cent of couples experience infertility. While this can be related to male or female aetiology, female infertility accounts for approximately 65 per cent of cases.

Couples trying for a pregnancy may present with subtle signs, existing diseases or medical history suggestive of subfertility. Community healthcare professionals are encouraged to make a referral for tertiary assessment should a couple be unsuccessful despite six months of unprotected sexual intercourse.


Recognising causes of subfertility

Subtle signs and symptoms of subfertility can include:

  1. Irregular menstrual cycles – Women with irregular menstrual cycles can experience difficulty falling pregnant, as irregular menstrual cycles can be a sign of lack of ovulation. Where ovulation does not occur, there is no egg released to enable a pregnancy to take place.
  2. Dysmenorrhoea (painful menses) or dyspareunia (painful sex) – which can be a symptom of undiagnosed endometriosis. Endometriosis affects the pelvic peritoneum and decreases the chance of pregnancy.
  3. History of ovarian cysts and / or surgery for ovarian cysts – All of a woman’s eggs in her lifetime are stored in her ovaries. Some ovarian cysts, like endometriotic cysts, destroy the eggs in the ovary; surgery that is carried out on the ovary can damage the remaining eggs. These factors can invariably reduce the quantity of viable eggs in the ovarian reserve.


In addition, misconceptions can contribute to subfertility in couples seeking to fall pregnant. These can include:

  1. The belief that In-Vitro Fertilisation (IVF) will guarantee a pregnancy – Some couples may put off childbearing until their mid-thirties and older, with the assumption that assisted reproductive methods such as IVF can guarantee a baby. However, there is no guarantee of success with any fertility treatment – the average success rate of IVF is 30 to 40 per cent, and the older the woman, the lower the success rate.
  2. The belief that having sex on the day of ovulation is sufficient for pregnancy – A common belief is having sex once, on the day of ovulation, will be sufficient for pregnancy. In reality, to have the highest chance of pregnancy, couples should have sex every two to three days during the fertile window (the seven-day period which ends on the day of ovulation). The reason for this is that sperm survives in the reproductive tract for up to five days, while the egg only survives for 24 hours after ovulation.


Investigating subfertility: A radiological approach

Female subfertility can be due to various causes, and may involve the endometrium, uterus, cervix, fallopian tubes and ovaries. Hence, in addition to clinical examinations and blood tests, targeted imaging investigations play a critical role in diagnostic assessment and treatment planning.

Types of imaging modalities used for female infertility investigations include ultrasound and ultrasound-based procedures such as saline infusion sonohysterography (SIS), hystero-salpingo foam contrast sonography (HyFoSy), hysterosalpingography (HSG) and pelvic magnetic resonance imaging (MRI). These modalities and their diagnostic roles are described in Table 1.


Table 1. Imaging modalities and diagnostic roles for female subfertility assessment

Ultrasound pelvis examination ​Saline infusion sonohysterography (SIS) ​Hysterosalpingography (HSG) ​Hystero-salpingo foam contrast sonography (HyFoSy) ​Pelvic magnetic resonance imaging (MRI)
​Type of procedure​A baseline investigation for subfertility performed using a trans abdominal or trans vaginal approach, or both.​A procedure where saline is injected into the endometrial cavity through a fine catheter under ultrasound guidance.​A procedure where iodinated contrast is injected into the uterine cavity using a fine catheter under fluoroscopy.​A new technique alternative to HSG, HyFoSy is a combined procedure consisting of SIS, followed by tubal patency assessment under ultrasound guidance in one sitting, using non-embryo-toxic gel as a contrast media.​A procedure mainly used in cases where uterine or tubal congenital abnormalities are suspected.
Diagnostic role

​Can detect:

  • Structural anomalies of the uterus, such as congenital anomalies
  • Myometrial abnormalities, such as fibroids and adenomyosis
  • Endometrial abnormalities, such as intracavitary lesions, including submucosal fibroids, polyps and adhesion
  • Ovarian and tubal abnormalities

​Can detect:

  • Endometrial lesions
  • Structural anomalies of the uterus, such as congenital anomalies

​Can assess:

  • Fallopian tube patency


Can demonstrate:

  • Uterine abnormalities, such as congenital uterine malformations and intracavitary lesions

​Can assess:

  • Fallopian tube patency
  • Structural anomalies of the uterus, such as congenital anomalies
  • Endometrial lesions

​Can detect:

  • Uterine/ tubal congenital abnormalities


Can characterise:

  • Adnexal lesion
​Accuracy​Preliminary evaluation of endometrial lesions

​High degree of diagnostic accuracy in the detection of intrauterine lesions

  • Sensitivity: 88%1
  • Specificity: 94%1

​High degree of diagnostic accuracy in the detection of tubal patency

  • Sensitivity: 94%
  • Specificity: 95%

​High degree of diagnostic accuracy in the detection of tubal patency

  • Sensitivity: 95%2
  • Specificity: 95%2


Diagnosing and treating tubal occlusion/obstruction

Obstruction of the fallopian tubes is one of the major causes for female subfertility, and assessment of fallopian tube patency is a crucial part of routine investigations. Traditionally, HSG has been performed to check for tubal patency. With high sensitivity and specificity of diagnosis, HSG can also demonstrate uterine abnormalities such as congenital uterine malformations and intracavitary lesions.

More recently, HyFoSy has been found to be an accurate test for tubal patency assessment with sensitivity and specificity similar to that of HSG2. It has also been found to be less painful and less time-consuming for patients, compared with HSG3, and carries no radiation risk.


Fallopian Tube Recanalisation

Where a patient has been diagnosed with tubal occlusion or obstruction, fallopian tube recanalisation (FTR) under fluoroscopic guidance (x-ray) can be performed to unblock fallopian tubes by passage of a guidewire and catheter through the obstructed segment of the fallopian tube. The outpatient procedure is carried out under sedation, and takes approximately 1.5 to two hours in duration.

FTR can be used to treat proximal tubal obstruction caused by muscular, tubal or cornual spasms, viscid secretions, mucosal aggregates, amorphous debris or stromal oedema with good success rates of 71 to 92 per cent4.

The highest success rates of pregnancy following successful recanalisation are found in healthy, younger women and most pregnancies occur within the first year following recanalisation. While re-occlusion can occur in approximately 25 per cent of patients, the procedure can be repeated.


Case study: Fallopian Tube Recanalisation in a 40-year-old patient with tubal occlusion

A 40-year-old patient presented with subfertility at KKH, and underwent a hysterosalpingogram (HSG). The results showed a left tube with free intraperitoneal spillage (stick arrows in Figure 2A), indicating tubal patency. However, the right tube was not opacified (triangle arrows in Figure 2A), indicating non patency of the tube, which could be due to muscular spasms or a blocked fallopian tube.

Subsequently, fallopian tube recanalisation was successfully performed for the right fallopian tube (triangle arrows in Figure 2B), resulting in both fallopian tubes being patent with free spillage.


Figure 2A Figure 2B



While spontaneous pregnancy is always encouraged and preferred, for some, this may be challenging or not possible. The good news is that subfertility and infertility can often be assessed and appropriately treated. To optimise outcomes, patients should be encouraged to seek prompt medical advice and attention.


Dr Thida Win, Consultant, Department of Diagnostic and Interventional Imaging, KK Women’s and Children’s Hospital

A consultant with the Department of Diagnostic and Interventional Imaging at KKH, Dr Thida Win has a special interest is in women’s imaging, particularly in gynaecology and breast imaging. With a deep interest in research, Dr Win is currently involved in breast-related researches as a co-investigator.

Dr Win is also actively involved in the teaching of radiology and gynaecological residents, and is an Adjunct Assistant Professor at Duke-NUS Medical School. In 2014, Dr Win was appointed a National Examiner for Diagnostic Radiology, in collaboration with the American Board of Medical Specialties.

Dr Rohit, Consultant, Department of Diagnostic and Interventional Imaging, KK Women’s and Children’s Hospital

Completing his Bachelor of Medicine and Bachelor of Surgery (MBBS) in India, Dr Rohit underwent his training in radiology in Singapore, and subsequently completed the Fellowship of the Royal College of Radiologists (FRCR) and Master of Medicine (MMed) examinations.

With a special interest in paediatric and women’s radiology, Dr Rohit joined KKH in 2015, and is currently a Consultant with the department. Dr Rohit is also involved in the teaching of residents as an Adjunct Assistant Professor with the Duke-NUS Medical School.

Dr Chua Ka-Hee, Associate Consultant, Department of Reproductive Medicine, KK Women’s and Children’s Hospital

Dr Chua Ka-Hee works closely with the Department of Reproductive Medicine at KKH, and has a special interest in male subfertility. Dr Chua is also a member of the Royal College of Obstetricians and Gynaecologists.



  1. Diagnostic accuracy of saline infusion sonography in the evaluation of uterine cavity abnormalities prior to assisted reproductive techniques: a systematic review and meta-analyses. Seshadri S, El-Toukhy, Douiri A, Jayaprakasan K, Khalaf Y. Hum Reprod Update. 2015 Mar-Apr;21(2): 262-74
  2. Hysterosalpingography for diagnosing tubal occlusion in subfertile women: a systematic review with meta-analysis. Maheus-Lacroix S, Boutin A, Moore L. Hum Reprod. 2014 May;29(5): 953-63
  3. Hysterosalpingo-foam sonography, a less painful procedure for tubal patency testing during fertility workup compared with (serial) hysterosalpingography: a randomized controlled trial. Kim Dreyer, Renee Out, Peter G. A. Hompes, Velja Mijatovic. Fertility and Sterility. 2014 Sept;102(3):821-5
  4. Recanalization of Fallopian Tubes. Janet Cochrane Miller. Radiology Rounds. 2017 Feb; 15(2)