Conception: understanding the process

A complex process

Unassisted conception is a complicated combination of factors and timing. It can be described in five steps:

Chart explaining how pregnancy occurs

Step One

During the first half of the menstrual cycle, hormones stimulate growth and development of a single follicle within one of the ovaries. At the same time, another hormone stimulates growth of the uterus lining in preparation for the fertilized egg.

Step Two

When the egg cell matures, hormone levels surge and trigger the egg’s release. The exact timing of ovulation relates to a woman’s individual menstrual cycle (period). In an average 28-day cycle, ovulation occurs between days 14 and 16, day one being the first day of menstruation. The egg follicle bursts, releasing a fertile egg, which migrates to the fallopian tube. What’s left of the spent follicle helps produce a hormone, which prepares the endometrium or uterus lining for the implantation of the fertilized egg.

Step Three

En route from the fallopian tube to the uterus, the egg may be fertilized. Sperm can live within the human body for 48-72 hours. But of the countless sperm that make it to this stage, only one may penetrate the egg’s protective membrane and fertilize the egg. During fertilization, the couple’s genes combine to create an embryo.

Step Four

As the first few cells divide, the embryo continues its course toward the uterus. Just before implantation, it hatches from the egg’s protective membrane.

Step Five

Six days after fertilization, the embryo embeds itself into the nutrient-rich lining of the uterus. A placenta forms to exchange nutrients and gases between mother and embryo, and essential hormones are released to maintain pregnancy. If fertilization doesn’t occur, or if for some reason, the embryo fails to implant, the lining of the uterus is expelled, resulting in menstrual bleeding (your period) and the cycle starts again.

Conception difficulties are just as likely to affect men as they are women. Male infertility is the primary diagnosis in approximately 25% of cases and contributes to a further 15–25% of the remaining cases.3

The role of hormones

Achieving a pregnancy to a large extent depends on the successful interaction of the hormones that regulate the reproductive cycle in women and sperm development in men. Some hormones are produced come from two glands in the brain, the hypothalamus and the pituitary. Specific female hormones are produced in the ovaries, while men’s specific reproductive hormones come from the testicles.

Luteinizing hormone (LH)

  • In women, this hormone is necessary for the production of oestrogens and triggers the egg’s release from the ovary.
  • In men, it stimulates the production of testosterone, the hormone that helps maintain male sexual characteristics and bring sperm cells to maturity.

Follicle-stimulating hormone (FSH)

  • In women, FSH stimulates egg growth and development and contributes to production of oestrogen.
  • In men, it stimulates sperm production in the testicles.

Gonadotrophin-releasing hormone (GnRH)

Progesterone

  • This hormone prepares the lining of the female uterus for implantation of the fertilized egg.
Fertility declines with age. For a healthy woman, the chances of becoming pregnant during any month are about 20% at the age of 30.  The odds reduce to 5% by the age of 40.4 If you have been trying to get pregnant for six months and you are 35 or older, do not wait to seek medical advice.5

Maximizing your chances of conception

Deciding to investigate concerns you may have about fertility is a commitment to your future as a couple. It’s a subject that takes time to discuss, and a conversation millions of other couples have already shared.

There are plenty of reasons for optimism. Modern fertility treatments are very effective for a majority of couples.2 While you are trying to conceive, why not learn a little more about the journey.

 

1. J. Boivin, L. Bunting, J.A. Collins, K. G. Nygren. International estimates of infertility prevalence and treatment seeking: potential need and demand for infertility medical care. Human Reproduction 2007; 22: 1506-1512.  2. Pinbourg A et al, Prospective longitudinal cohort study on cumulative 5-year delivery and adoption rates among 1338 couples initiating infertility treatment. Hum Reprod.2009; 24: 991-999.  3. Collins J.A. Evidence-based infertility: evaluation of the female partner. International Congress Series 2004; 1266: 57–62.  4. Age and Fertility. A Guide for Patients. ASRM 2003; http://www.asrm.org/Patients/patientbooklets/agefertility.pdf  5. Definitions of fertility and recurrent pregnancy loss. Fertil Steril 2008; 90:S60.