Making Babies

Some couples have no issues making babies. They seem to get pregnant just by looking at each other. Other’s have difficulty getting pregnant. They try month after month with no results. With this in mind, lets talk about the menstrual cycle and how the cycle plays a part in getting pregnant.

The average cycle lasts 28-35 days so some women have a cycle monthly while others may not have a cycle every month if their cycle is longer. Did you know that by the 16th gestational week, females have about 7 million oocytes, which eventually turn into mature eggs. By birth, females have 1-2 million oocytes remaining. Generally, only 1 egg is released each month so most women only release 300-400 eggs during their lifetime.

Menstrual Phase

Menstruation is the first phase and begins with the first day of your period. Your period happens when the uterine lining, the endometrium, sheds.

Follicular Phase

During this phase, a follicule in the ovary ripens into the graafian follicle which increases estrogen levels and luteinizing hormone (LH). This in turn stimulates the endometrium to develop in preparation for a fertilized egg to implant. As estrogen increases, women will notice changes in their mucous which can help identify their ovulation and fertile time.

Ovulation Phase

Once mature, an egg will react to the luteinizing hormone surge and the estrogen. This reaction will cause the egg to leave its nice warm home in the ovary and begin its journey down the fallopian tube. Sometimes, more than one egg will be released. If all are fertilized, you’ll be the proud new parents of twins, triplets or higher multiples. Congratulations! The ovaries switch off which one releases eggs each cycle. This egg release is actually something called the graafian follicle bursting which is what propels the egg out of the ovary. This burst is actually very important because the ovary and fallopian tube are not connected so the momentum from the burst helps make sure the egg gets where it needs to go. Some women feel cramping on the side of the release from the rupturing follicle. This ruptured graafian turns into a glandular corpus luteum which increases estrogen and progesterone production. All of this is to prepare the uterus for a fertilized egg to implant in the endometrium.

Luteal Phase

Yay! Ovulation has begun. If the egg is not fertilized within 24 hours of being released, the corpus luteum turns into the corpus albicans and stops releasing progesterone and estrogen. Now your favorite monthly visitor, Aunt Flow, will come to say hello as the endometrium and unfertilized egg sheds and your cycle starts again.

During this phase, the fallopian tube helps to bring the egg down to the uterus. How does it do that? I hear you asking. There are thin hair-like protrusions called cilia lining the fallopian tubes. They do a waving, scooping motion which guides the egg down and at the same time guides the sperm up to the egg.

Fertilization

If you have sex and a sperm makes it to the egg during the luteal phase, then you have fertilization. Usually, fertilization will happen in the fallopian tube, about halfway between the ovary and the uterus.

Fun fact: Sperm can reach the fallopian tube in about 30 minutes and can survive around 3-5 days inside the fallopian tubes. WOW!

Men release millions of sperm when they ejaculate but only a few hundred actually make it to the egg. They work together to penetrate the egg. Remember that progesterone released by the corpus luteum? That progesterone helps the sperm become hyperactive and release a digestive enzyme that helps them dissolve the outer layer of cells around the egg. It takes lots of sperm to get through that outer layer but only one special wiggling sperm gets to join with the egg and form a diploid zygote.

This zygote starts to grow and transform immediately and continues to its final destination of the uterus.

Implantation

It’s been about a week since you ovulated, your endometrium is nice and thick. You’ve had sex and your egg is fertilized. Next step is for that fertilized egg, now called a blastocyst, to get a nice snug home in that endometrium.

How does your body know you’re pregnant? Well, the blastocyst releases a hormone called the human chorionic gonadatropin (hCG) to the corpus luteum which in turn continues to secrete progesterone and estrogen throughout the pregnancy.

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