The Fertility Center

A blog about fertility issues, treatments and trends from the specialists at Greenwich Fertility.

August 21, 2018

The Science of Getting Pregnant

By Laura Meyer, M.D.

We spend much of our reproductive lives AVOIDING pregnancy, when, in truth, it is much harder to become pregnant than we think!   Several factors must be aligned for efficient human reproduction, making the chances of pregnancy per month for most couples only 10-25% depending on age.  The following are key factors necessary for a healthy pregnancy and baby:

Egg quantity and quality:

A healthy pregnancy starts with egg and sperm.  Women are born with all of the eggs they will ever have and then lose them over a lifetime.  There are blood tests that can be done to determine your “ovarian reserve”, or remaining egg quantity. While these tests do not predict chances of pregnancy, they may influence timelines and medication protocols.  “Egg quality” usually refers to the genetics of the egg, and is directly linked to age.  As we get older, not only do we lose eggs, but the eggs that we retain age, resulting in more genetically abnormal eggs. These abnormal eggs will either will not fertilize, will fertilize and not implant, or will fertilize, implant and lead to a miscarriage.  This is why pregnancy rates decline and miscarriage rates rise as we get older. Women who plan to delay child bearing into their late 30’s and 40’s should consider a method of fertility preservation such as egg or embryo freezing.

Normal Sperm:

Achieving pregnancy requires sperm, in adequate quantities, with tails that move in a certain way, and heads shaped in a certain way that give them the ability to penetrate and fertilize an egg.  Sperm can live in the uterus for up to 3-5 days, which is why intercourse every other day during the “fertile window” is adequate.

Open fallopian tubes and a normal uterus:

Once an egg ovulates (leaves the ovary), it is released into the pelvis, where it is picked up by one of the fallopian tubes.  If sperm is present, it travels to the tube to meet the egg, fertilizes it, creating an embryo, which will then travel through the length of the tube and into the uterus in order to implant.  Blocked or damaged fallopian tubes or a uterus with significant abnormalities may prevent a normal pregnancy from implanting and developing.

Ovulation and timing of intercourse:

There is really only a narrow window of a few days during which time pregnancy can be achieved. Ovulation happens when an egg, which has reached peak maturity, triggers the brain to release a hormone (luteinizing hormone-what most ovulation kits test in the urine) that leads to final egg maturation and eventual release from the ovary.  Timing of ovulation usually happens in the mid-cycle, which varies depending on how long the cycle is (“cycle length” is the length of time from the first day of a period to first day of the next period).  In some women, who have shorter cycles, ovulation can occur as early as day 8 or 9, while others, who may have longer cycles, may not ovulate until day 20 or beyond.  Most women with regular cycles ovulate anywhere form cycle days 10 to 16.  If you have regular cycles, intercourse every other day from day 10 to 16 should cover the “fertile window.”  If you have an irregular cycle or do not know when you ovulate, consider seeing a reproductive endocrinologist for better understanding of your cycle and to help with timing of intercourse.

Trying to conceive can be challenging and anxiety provoking.  If you are under 35 and have been trying for more than one year, over 35 and have been trying for more than six months, or just started trying and are concerned about something being “off” and are just curious about your fertility, seek consultation with your OB/GYN or Fertility doctor.  Understanding your body and having a plan can relieve this anxiety and increase your chances of success.

For more information, or to schedule a consultation with a fertility specialist please contact Greenwich Fertility.

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