Ovulation, Fertility, and Pregnancy: What It Really Takes To Make a Baby


If you were to judge fertility rates solely by the number of pregnancy announcements in your social media feed, you might think making a baby is a piece of cake. But in reality, the complex chain of events that has to occur in order for conception to take place makes pregnancy a pretty incredible feat.  

“When you think about all the things that have to go right for a pregnancy to start, it’s amazing that the human race is able to reproduce at all!” says Kate White, MD, MPH, assistant professor of obstetrics and gynecology at Boston University.

In fact, a healthy 30-year-old woman only has a 20 percent chance of getting pregnant during her cycle, according to the American Society for Reproductive Medicine. But don’t panic—that’s in each cycle, not overall. In fact, 85 percent of women with no fertility issues will conceive within a year of trying. However, the rate does decline to about five percent per cycle by the time a woman is 40 years old.

Every woman is unique and has her own fertility story, but understanding the intricacies of fertility may help you make more informed decisions.

How Many Eggs Does a Woman Have?

When women are born, their two ovaries contain 1-2 million eggs. By the first menstrual period, about 400,000 of those eggs are left; the rest are absorbed by the ovaries. Only about 300 to 500 of the eggs will mature enough to be released in ovulation during a woman’s lifespan.

“And no, suppressing ovulation by using birth control doesn’t ‘save’ your eggs for future use,” says White. “It’s not like a bank—it’s use them or lose them!”

What Happens During Ovulation

In order for ovulation to take place, one of your ovaries has to release an egg (experts used to think the ovaries took turns each cycle, but either one may be the one to ovulate). This happens when your brain produces follicle stimulating hormone (FSH), which stimulates the follicles to develop and cause estrogen to rise. A different number of follicles develop each month, but out of all of these contenders, there’s usually just one that grows faster than the others and becomes the “dominant” follicle (it’s possible to have two dominant follicles release eggs—that’s how you get fraternal twins!).

“Think of follicle recruitment as a beauty pageant,” says White. “No matter how beautiful all the contestants are, there’s only one winner. And when one takes the crown, the rest fade to the background.”

As the dominant follicle grows, it causes estrogen levels to rise, which starts to inhibit FSH secretion. As FSH falls, the other smaller follicles die off, and only the dominant follicle continues to mature.

When estrogen reaches its peak, it causes a surge of luteinizing hormone (LH) that triggers the dominant follicle to finish maturing and release its egg. That egg then travels through the fallopian tube for about 12 to 24 hours. If the egg is fertilized by a sperm cell, it implants itself in the uterine wall and starts a pregnancy. If it isn’t fertilized, it’s shed with the rest of your blood and tissue during menstruation.

Quick note, though: Your fertile window is actually about six to seven days (not 12 to 24 hours) because sperm can live for up to five days after sex. That means it’s possible to get pregnant if you have sex during the five days before ovulation, on the day of ovulation, or on the day after (though pregnancy is less likely to occur the day after).

What Can Affect Fertility?

A variety of medical conditions can affect your fertility, including:

  • Conditions that affect ovulation such as polycystic ovary syndrome, too much of a hormone called prolactin, and too much/too little thyroid hormone.
  • Conditions that affect the movement of eggs and sperm in your fallopian tubes such as endometriosis, pelvic inflammatory disease, or an abnormality in the fallopian tubes that causes a blockage.
  • Conditions that affect the inside of the uterus such as fibroids, polyps, or adenomyosis (a condition in which the inner lining of the uterus breaks through the muscle wall).

Age also has an impact, with fertility usually starting to decrease by the time a woman reaches her early 30s and declining more significantly around age 35. This is due to natural changes that affect the ovaries and compromise the quality of the eggs, even if your periods remain regular.

As you approach menopause, you may also not ovulate every cycle, making it harder to get pregnant. Older women who do conceive are at higher risk of having miscarriages and/or giving birth to babies with genetic problems like Down syndrome. However, it’s important to remember that each and every person is different, and many women in their 30s and 40s do successfully conceive and deliver healthy babies.

“I got pregnant my first month off the pill at age 34,” says White. “And most of my doctor friends also had their kids in their late 30s.”

Lifestyle factors can impact your chances of getting pregnant, too. Some factors that are known to negatively influence fertility include:

  • Smoking
  • Drinking alcohol excessively
  • Weighing much more or much less than your ideal body weight
  • Having an eating disorder
  • Exercising excessively
  • Experiencing intense stress

Bottom line: “The best way to be healthy for a baby is to be as healthy as you can for yourself,” says White.

30 Comments   Join the Conversation

30 CommentsLeave a comment

  • Wow, this is condescending. Beauty pageant? Really? And what’s with wagging a finger at users for imagining that birth control will “save” their eggs? I’ve never in my life heard people ask about that, and I’ve spent a lot of time in groups discussing various aspects of reproductive health.

    I like the idea of having articles, but not at the expense of actually developing this part of the app (which isn’t even at beta stage yet), and don’t write them like this.

    • Completely agree! It’s bad enough they’re calling this female health, as if all uterus owners are female (or that if you don’t have periods you can’t participate in being female), but also having these gross ideas of “female” shoved in there is even worse – What can all women imagine? Ah, yes, a beauty pageant. With one winner. Always. Even though we literally just stated twins are a thing.

      • I feel that you have a higher level of education than most. As an OB/GYN nurse there are patients that gave little or no knowledge or even inaccurate knowledge of the female reproductive system. There were also women that outshined me in female reproductive knowledge. Though I don’t agree with all of the examples and analogies in this article you have to understand the its trying to appeal to as many as possible but can not appeal to everyone, that would be a sheer miracle.

    • I had an OB/Gyn tell me at age 42 that there was no rush for me to get pregnant- that I had plenty of time and that my eggs were fresh because I had been on the pill since I was 19.
      I’d never been pregnant.
      Yep, for real. That was in 2001.
      In 2002, Thank God my endocrinologist told me that was BS and to stop taking the pill right then and there. I got pregnant the next month by carefully tracking my ovulation. However my baby died at 14 weeks.
      I was able to get pregnant the next year, but had an early miscarriage.
      I was never able to get pregnant again.
      Not having children is the greatest tragedy of my life.
      I became seriously ill a few months later and have been disabled ever since.
      So yeah, it’s a real thing that drs tell women that.

      • Hi. I’m sorry for your loss. Sincerely. I had a bad accident mid-October (many years ago) that stunted my husband’s and my plans of watching our health (including drinking alcohol) which is why we decided to start trying Jan 2nd, after his birthday a month later, and the hustle and bustle (and holiday parties and get-togethers) during the holiday season. After a three year recovery and minor but life-altering disabilities attained from the accident, a few years later my hubby said we were Not going to have children! However, now I have 3 ‘fur babies’ and the last rescue kitty brings me so much joy! ☺️ 1) Have you ever thought that your becoming ‘seriously ill’ after your miscarriage had something to do with with whatever your illness and your subsequent disability may have been the reason for your miscarriage? (maybe even though You didn’t know, your body knew that your baby wouldn’t be normal in some way, hence the miscarriage? (You know the saying “Everything happens for a reason “, right)? Just asking because I didn’t want to get a divorce, but choosing to stay with my husband meant not even Trying to have children anymoreI later told him that that was the only thing in life I Wanted, but didn’t get☹️ So I feel your pain, and I applaud you for making sure people get the facts straight via this community forum here. If you were in a relationship at that time (when all this happened with you), are you still together now?

    • I feel that you have a higher level of education than most. As an OB/GYN nurse there are patients that gave little or no knowledge or even inaccurate knowledge of the female reproductive system. There were also women that outshined me in female reproductive knowledge. Though I don’t agree with all of the examples and analogies in this article you have to understand the its trying to appeal to as many as possible but can not appeal to everyone, that would be a sheer miracle.

  • Does the new update allow you to mark that you are pregnant? Im not seeing an option to anywhere but thought I would ask.

  • I would also love to see a pregnancy option or setting. Couldn’t find one in the new female health section.

  • Hi it would be useful to be able to put in opk results as I ovulate later than most people day 20/21 and have a shorter than average luteal phase. Having a set date is not a great idea as if I didn’t use opks and other apps I would miss my fertile window each month and take pregnancy tests too early (it could cause discouragement to newbies of ttc). Also like above-mentioned a hey I’m pregnant date setter would be good too. Also being able to put in past cycles would be great too so it can build a better picture of me more quickly. I’m loving the changes so far though

  • Thanks for writing this article and interviewing the obgyn. I hadn’t thought about birth control “saving” the eggs but it is a logical thought particularly for those who don’t have a period while taking it. That is something worth noting. I have a couple of friends who wish they could attribute their weight gain to their current pregnancies. Maybe that could be added.

  • Agreed with other commenters that it seems strange and unfortunate that part of an app tracking “female health” and specifically looking at fertile windows wouldn’t let you input pregnancy.
    Kind of a major thing to miss, guys (guys? Is that the problem here?)

  • I ovulate late in my cycle (on day 20). Is there a way to change this date in the app so it’s accurate to me?

  • Can we please have an option to put in our own ovulation date. I know for a fact that I ovulate a lot later than what it’d predicting and it’s really frustrating not being able to be accurate with this information. Just look at any other decent period tracking apps to see what’s actually important here please. It’s a good start but I’d love you to improve on it please!

  • So multiple issues with this app. I use a different one to track everything.
    1: no option to put I am pregnant.
    2: does not account for people who don’t have predicted cycles. I can have a cycle from anywhere from 28 to 160 days between periods. This app makes you select yours

    1: add an I’m pregnant button. Then allow it to put in your due date or conception date so it’s accurate.
    2: include a predict cycle option. This will allow people with medical conditions like PCOS or thyroid or endometriosis to be able to add it when they get it.

    If you would like to see a good app for fertility and pregnancy see an app called “my calander”. Fully customizable and accurate.

  • I’d love to see an option to mark pregnancy/miscarriages. Unfortunately I suffered a miscarriage and would like that noted so it doesnt show me that a have a very long period cycle.

    My average is 25 days. Currently fitbit shows 40day cycles.

  • Good idea but you’re missing the body basal temperature and cervical mucus tracking which both indicate fertility and ovulation. Important for preventing pregnancy and trying to get pregnant. I would imagine you would also want to track protected and unprotected intercourse

  • I can’t get pregnant and would like the option for just period tracking. Kind of offensive that there’s no option to shut it off without losing all predictions.

  • I’m confused as to why I can track everything apart from my pregnancy! I’m 3 weeks from giving birth and have found it so frustrating not being able to log this on my app. Pregnancy changes everything, sleep, heart rate etc. Seems silly that I can log about my sex life, fertility but not log my pregnancy.

  • Whilst I think this is a great feature I would like to have the option to turn it off. All I want to track is my cycle length and period, to help me keep track of irregularities and help predict my next period.

  • I would like the opportunity to add my own ovulation day because I ovulate earlier than day 14 and am currently trying to get pregnant. I’d like to use the Fitbit app to track my cycles but it doesn’t fit my needs.

  • what I have learned from watching other people is to never tell anyone what your intent is for your funhouse. Don’t tell anyone you are “trying”. Its not their business. In fact, if I were coupled up and people were asking me “When are you gonna have kids?” I’d say something snarky as a response. My fondest wish is to break the universe of the habit of asking that question. It Is No One’s Business. Period.

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