What Is Ovulation?

A woman has two ovaries, located beside the uterus (womb). The ovaries are responsible for producing eggs and female hormones.

At birth, the ovaries contain thousands and thousands of pre-eggs or primordial follicles. Each month, in women with regular menstrual cycles, several of these egg cells start developing and are surrounded by fluid and become small follicles (antral follicles). One of these follicles will accelerate in growth, mature then rupture to release an egg. This is termed ovulation.

Female Hormones

The pituitary gland, located at the base of the brain, produces both follicle-stimulating hormone (FSH) and luteinizing hormone (LH). Under the influence of FSH and LH, between 10 and 20 follicles (immature eggs), will start developing, and then the ovaries will select one follicle, the lead follicle, to mature, which will eventually ovulate.

The two most important hormones produced by the ovaries are estrogen and progesterone. Both are important for a successful conception. Estrogen promotes final growth of the ovarian follicles and helps the endometrium to increase in thickness. Progesterone, which is released after ovulation, is primarily responsible for preparing the endometrium for implantation of a fertilized egg.

Why Is Ovulation Essential For Reproduction?

For a woman to have a chance to conceive, she must ovulate. At ovulation, the fallopian tubes will hover over the ovaries and transport the mature egg into the fallopian tube. If the egg comes into contact with sperms, fertilization can occur and there is a chance the woman can become pregnant.

The egg remains in the tube for a few days but the actual period of time for which it is fertilizable is very short, normally less than 1-2 days. If the egg does not meet any sperms, it will break down in the tube and be naturally resorbed.

Who May Need Ovulation Induction Treatment?

Women with Hormonal Disorders Causing Anovulation

  • Hypothalamic pituitary problems which result in insufficient production of LH and FSH
  • Hypothyroidism with low levels of thyroid hormone
  • Overproduction of prolactin hormone
  • Excessive androgen, the male sex hormone, levels can suppress FSH production and ovulation

Women With Polycystic Ovary Syndrome (PCOS)

  • PCOS women frequently do not ovulate and may have hormonal imbalances such as reversal of LH/FSH ratio and excessive androgen

Women With Irregular Menses

  • Low egg reserves
  • Impending premature menopause
  • Extreme obesity / extreme underweight

Make an appointment online or contact the fertility clinic to consult a fertility specialist.

Fertility Medications

Clomiphene Citrate (Tablets)

This is the most common fertility medication used to induced ovulation. These tablets are taken for five days each menses cycle, usually from 2nd day of your cycle. Four out of five women taking Clomiphene Citrate will ovulate but only a third will become pregnant.

Possible side-effects with Clomiphene Citrate include hot flushes, headaches, dizziness, breast discomfort and stomach upsets. There is also 10% risk of multiple pregnancy, mostly twins.

If you are not ovulating while on Clomiphene Citrate treatment, your doctor may need to increase the dosage of your medications or consider gonadotrophins to help you ovulate. If you are ovulating but have yet to conceive within 3 to 6 months of treatment, you should consider being investigated for other causes of infertility.

Gonadotrophins (Injections)

Gonadotrophin preparations are synthetically produced hormones used to induce ovulation in women when simpler methods have failed. These injections are started a few days after the onset of a menses. The dose given will vary from patient to patient, depending on your age, egg reserve test results and the purpose for the treatment.

Ultrasound scans are used to monitor the ovarian response and the dosage and duration of the injections are adjusted based on the results of these ultrasound scans.

The main risk from gonadotrophin injections includes cancellation of your treatment cycle when too many follicles have developed and in rare cases, ovarian hyperstimulation syndrome (where there is excessive fluid accumulation in the lungs and abdomen).

Side-effects of these daily injections include pain and redness of the injection site and of course, multiple pregnancies, when more than one egg becomes fertilized and gets implanted.

Multiple pregnancies are high-risk pregnancies as they are associated with increased risks of miscarriage, fetal anomalies, premature births and low birth weight.

Monitoring Treatment

The best way to monitor the ovaries’ response is by ultrasound, the scan will show on the ultrasound screen how many follicles are growing in each ovary. Each mature follicle should contain one egg. Careful monitoring will help to prevent the development of too many eggs.


  • Other fertility medications (metformin, letrozole)
  • Address weight issues
  • Correct hormonal disorders
  • Laparoscopic ovarian drilling for PCOS women in whom fertility medications are not suitable or have failed.

Step By Step Ovulation Induction

1. Drug treatment, to produce one to two mature eggs to mature

  • Clomiphene citrate or preferably gonadotrophins to stimulate the growth of one to three follicles at the most.

2. Monitoring of treatment, to measure the growth of follicles, individualise drug doses, and prevent serious side effects

  • By transvaginal ultrasound scanning
  • Sometimes by measuring oestrogen levels in a blood sample

3. Administering hCG when the lead follicle reaches a diameter of between 16mm to 26mm

  • hCG encourages the final maturation and release of the dominate follicle
  • when 3 or more follicles > 15mm have developed, hCG administration may be withheld in order to prevent serious side effects such as multiple pregnancies

4. Sexual intercourse or IUI is timed 36–40 hours after the injection of hCG (best timing: 36–40 hour)

5. Pregnancy testing / monitoring

Make An Appointment

Make an appointment online or contact the fertility clinic to consult a fertility specialist. Under Specialist Appointment Details, select "Assisted Reproductive Medicine" or "Obstetrics, Gynaecology & Fertility".

Contact Raffles Fertility Centre

Make an enquiry if you require more information.

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