What Happens During the First Week of Pregnancy

Believe it or not, your pregnancy journey begins now, even though you're not actually pregnant yet. That's because most practitioners start timing pregnancy based on the first day of your last menstrual period (LMP).

In weeks 1 and 2 of pregnancy, your body is gearing up for ovulation and preparing for fertilization, which will happen in week 3.

Your Baby at Weeks 1 and 2

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This week the groundwork is laid for the big O — ovulation — the all important first step toward the making of the baby of your dreams. And like those dreams, the baby action is all in your head right now — where the hypothalamus, the control center in your brain, works with its partner in reproduction, the pituitary gland, to start releasing hormones.

These hormones — called FSH and LH — prompt the ovaries to get cracking on some eggs, ripening one to maturity within its follicle. All this egg action causes the ovaries to crank up production of two other powerful hormones, estrogen and progesterone. These hormones, the dynamic duo of the reproductive system, get the reproductive party in your uterus started, telling the uterus to thicken its lining, forming a blood-pumped cushion in anticipation of hosting a fertilized egg.

Midway through your menstrual cycle — around day 14 if you have an average 28-day cycle — the dominant follicle in the ovary swells and then ruptures, releasing the mature egg of the month. That egg, the one with your baby's name on it, bursts through the walls of the ovary and is immediately swept up into the fringed opening of the fallopian tube, where it will take a six day odyssey down to the uterus. Ovulation has just occurred.

Meanwhile, swimming along as fast as their little tails can flutter, millions of sperm are making a beeline for that egg, up through the cervix, into the uterus, and then on to the fallopian tube. One especially persistent suitor survives the grueling journey to intercept the egg and burrow into its outer layers. The victorious sperm plunges into the egg's nucleus, releases its own genetic contribution, and bingo! the egg is officially fertilized. That twinkle in your eyes is about to become…a baby.

At a Glance

Baby brain boost

Protect unborn brains! Women who get 400 micrograms of folic acid daily this early on reduce baby's risk of neural tube defects by up to 70 percent.

Chance of twins?

Twin alert! If you're over the age of 35 you produce lots of follicle-stimulating hormones and more follicles, upping the chance that two or more eggs will be released during ovulation.

You're pregnant! Or are you?

Surprise: You're not actually pregnant during your first week of pregnancy! Your due date is calculated from the first day of your last period.

1 to 2 weeks pregnant is how many months?

If you're 1 and 2 weeks pregnant, you're in month 1 of your pregnancy. Only 8 months to go! Still have questions? Here's some more information on how weeks, months and trimesters are broken down in pregnancy.

Gearing up to ovulate

No, there's no baby or embryo in sight. At least not yet — just an anxious egg and a whole bunch of eager sperm at their respective starting gates.

But in weeks 1 and 2 of pregnancy — the week of and immediately following your last menstrual period — your body is working hard to gear up for the event that paves the way for baby: the big O, or ovulation.

Right now, your uterus has begun preparing for the arrival of a fertilized egg, though you won't know for sure if that egg has successfully matched up with sperm until next month.

Calculating your due date

How can you call this your first week of pregnancy if you're not even pregnant? It's extremely hard for your practitioner to pinpoint the precise moment pregnancy begins (when sperm meets egg).

While there's no mistaking the start of your period, the exact day of ovulation can be hard to nail down. What's more, sperm from your partner can hang out in your body for several days before your egg comes out to greet it. Likewise, your egg can be kept waiting for up to 24 hours for late sperm to make their appearance.

So in order to give all pregnancies some standard timing, most practitioners use the first day of your last menstrual period as the starting line of your 40-week pregnancy. Still confused? Think of it as a head start — you're clocking in roughly two weeks of pregnancy before you even conceive!

Your Body at Weeks 1 and 2

Your last menstrual period

You've just gotten your last period, at least for a while: The lining of your uterus is shedding, taking with it last month's unfertilized egg. But that's not all that's happening. A new cycle is beginning, one that is the starting point for your pregnancy.

Your menstrual cycle is orchestrated by a symphony of hormones working in concert with one another. The first to kick in is FSH (follicle stimulating hormone) which — you guessed it — stimulates the follicles to mature, some faster than others.

A second hormone, lutenizing hormone (LH), increases around day 5 and also works with FSH to stimulate the follicles. Each follicle contains an egg, and each month only one follicle becomes the dominant one, destined for ovulation.

As the follicles mature, they produce another hormone, estrogen, which does two things. First, it encourages the lining of the uterus to begin thickening again. Second, once a high enough level of estrogen is reached, it will trigger a spike in the production of LH.

That surge of LH causes the egg from the most mature follicle to burst through the ovarian wall (a process you probably know best as ovulation, which generally occurs about 24 to 36 hours after the LH surge) to meet Mr. Right — the lucky sperm that will turn that eager egg into a baby-in-the-making and make your body's prep work worth all the effort.

Believe it or not, the countdown to delivery day begins now, during the period before fertilization — even though egg and sperm haven't even been in the same room (or womb!).

And if you don't get pregnant this time around, don't stress: The average, healthy couple in their 20s and early 30s have about a 25 to 30 percent chance of getting pregnant with each cycle.

In the meantime, while your uterus is preparing for its new tenant, be a good landlord. Think of these two weeks of waiting as a final walk-through before baby takes over the keys. You may not technically be pregnant yet, but it isn't too early to act like you are. Start taking your prenatal vitamin, give up alcohol and smoking and embark on a healthy prenatal diet and exercise routine.

Turn down the heat to boost fertility

Trying to make a baby? Turn off that electric blanket and keep each other warm the good, old-fashioned way. Studies show that prolonged, excessive heat — like the kind produced by electric blankets, heating pads, heated seats and even laptops that are placed on a man's lap — can adversely affect those temperamental testes by slowing down sperm production (and you want sperm aplenty right now!). Plus, all that snuggling you'll have to do to stay warm will generate the kind of heat that can actually make babies.

More ways to increase your odds of scoring a fertilized egg: Try refraining from oral sex before the main event, since saliva can have a negative impact on sperm activity and motility … and you want them alive and kicking. Ditto for most lubricants, so lay off the Astroglide while you're trying to conceive.

Pregnancy Symptoms Week 1 and 2

Your temp drops, then spikes

Your basal body temperature, or BBT, dips to its lowest point just before you ovulate, then immediately shoots up about a half a degree as soon as ovulation occurs. So buy a special digital basal thermometer and start tracking! Over the course of a few months, you'll be able to notice a pattern to better predict when that magic moment happens to you each month (and when to jump into bed!). Read More

Increased cervical mucus

If you've been monitoring your mucus during these TTC months, you already know that it changes consistency from week to week. Right now your mucus is probably thick, sticky and creamy, but as you head toward C-day (conception), the volume will increase and it'll start to look cloudy. Read More

Tips for You This Week

Fill up on folic acid

There's no doubt that your body works overtime when you're expecting — so help give it the extra nutrients it needs to baby-build by getting 400 to 600 micrograms of folic acid daily from all sources, including your prenatal vitamin and folate-rich foods.

Research has shown that taking folic acid beginning when you're trying to get pregnant and continuing daily throughout pregnancy not only helps you conceive but has important health benefits for expecting women and their babies.

Folic acid (and its natural form, folate) can help reduce the risk of birth defects including congenital heart and neural tube defects in your baby, and has even been shown to lower your chances of gestational diabetes, preterm labor and miscarriage.

Ask your doc about meds

If you're taking a prescription, OTC or herbal med, ask your doctor ASAP about whether it's safe to continue it during pregnancy.

Herbal preparations are not tested or approved by the Food and Drug Administration (FDA) and are not required to undergo clinical trials. Translation: Their safety, or lack thereof, is unknown.

Even herbs that you've heard could be helpful during pregnancy may be harmful at some point during the next nine months. So always get the green light from your practitioner before taking any medication or herbal supplement of any kind.

Spot early pregnancy signs

You could be weeks away from taking a pregnancy test, but Mother Nature may give you a heads-up in the form of early pregnancy symptoms.

Some, like a heightened sense of smell and tender breasts, can show up before you even miss your period, while others, like spotting and urinary frequency, happen a week or two after conception.

Haven't noticed any new symptoms? Plenty of women won't feel any until at least a few weeks or more into their pregnancies — and some lucky few won't notice any at all!

Shop for pregnancy tests

You're already imagining the moment when those magical double lines, plus signs or "yes" answers appear on your home pregnancy test. But before you get to that point, you'll have to navigate the drugstore aisles to choose the one you like best.

One question you might have: Are cheap pregnancy tests any different from expensive ones? Not really. All home pregnancy tests work the same way — by measuring the levels of the pregnancy hormone hCG — and are up to 99 percent accurate if you follow the instructions.

Some pricier tests might be more sensitive to hCG than others, or work a little faster. But rest assured, whether you choose a $5 or $25 test, your results will be equally accurate.

Brush up on your pregnancy hormone knowledge

Your hormones will be to blame for pretty much every pregnancy symptom you'll experience for the next nine months or so — which is why it makes sense to familiarize yourself with some of the major pregnancy players.

Stuffy nose? Credit all that extra estrogen, which is helping the uterus grow and baby's organs form. Facial fuzz sprouting? Thank prolactin, which helps enlarge your breasts and kickstarts lactation.

Achy back and joints? That would be the handiwork of the hormone relaxin, which (true to its name), helps loosen the muscles, joints and ligaments in your body to prepare for labor.

Are those signs of conception...or just PMS?

Early pregnancy signs — like bloating, fatigue and tender breasts — are remarkably similar to PMS symptoms and can appear the week before your last period arrives.

Other symptoms, like a consistently creamy vaginal discharge or an elevated basal body temperature (BBT), are usually signs of pregnancy, but can be tricky to detect.

One symptom that only appears during pregnancy: a change in your areola's color or size (they'll look darker or wider).

Look for signs of ovulation

Be an ovulation detective. At peak fertility — which, depending on how long your menstrual cycle lasts, is 11 to 21 days from the first day of your last period — your cervical mucus increases and becomes thinner, gooey and slippery.

To figure out when you're ovulating, you can use an at-home test called an ovulation predictor kit, which works by measuring the levels of luteinizing hormone (LH) in your urine.

Other signs of ovulation to watch out for include slightly lower basal body temperature (that then rises again), light spotting, cramps in your lower abdomen and an increased sex drive.

From the What to Expect editorial team and Heidi Murkoff, author ofWhat to Expect When You're Expecting. What to Expect follows strict reporting guidelines and uses only credible sources, such as peer-reviewed studies, academic research institutions and highly respected health organizations. Learn how we keep our content accurate and up-to-date by reading our medical review and editorial policy.

• What to Expect Before You're Expecting, 2nd edition, Heidi Murkoff.
• What to Expect When You're Expecting, 5th edition, Heidi Murkoff.
• WhatToExpect.com, Ovulation Symptoms, September 2020.
• WhatToExpect.com, 9 Early Signs of Pregnancy Before a Missed Period, February 2020.
• WhatToExpect.com, How to Use Ovulation Test Strips to Predict Your Most Fertile Days, April 2020.
• WhatToExpect.com, Pregnancy Tests, September 2020.
• WhatToExpect.com, What Is the Difference Between Cheap and Expensive Pregnancy Tests?, April 2020.
• WhatToExpect.com, Cervical Mucus and Pregnancy, April 2020.
• WhatToExpect.com, Back Pain During Pregnancy, January 2020.
• WhatToExpect.com, Are Herbs Safe for Pregnancy Symptoms?, May 2021.
• WhatToExpect.com, Your Guide to Pregnancy Hormones, January 2021.
• WhatToExpect.com, How Many Weeks, Months and Trimesters in a Pregnancy?, June 2020.
• WhatToExpect.com, Folic Acid During Pregnancy, March 2021.
• Centers for Disease Control and Prevention, Women Need 400 Micrograms of Folic Acid Every Day, April 2021.
• National Institutes of Health, National Library of Medicine, The Paradox of Declining Fertility But Increasing Twinning Rates With Advancing Maternal Age, June 2006.
• Cleveland Clinic, Fetal Development: Stages of Growth, April 2020.
• American College of Obstetricians and Gynecologists, Fertility Awareness-Based Methods of Family Planning, January 2019.
• Merck Manual, Female Reproductive Endocrinology, March 2019.
• National Institutes of Health, National Library of Medicine, Detection of Ovulation, a Review of Currently Available Methods, September 2017.
• American Society for Reproductive Medicine, Age and Fertility, 2021.
• Mayo Clinic, Low Sperm Count, October 2020.
• Cochrane, Vitamin Supplementation for Preventing Miscarriage, May 2016.
• JAMA, Plasma Folate Levels and Risk of Spontaneous Abortion, October 2002.
• Food and Drug Administration, What You Need to Know About Dietary Supplements, November 2017.
• Centers for Disease Control and Prevention, Substance Use During Pregnancy, July 2020.

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What Happens During the First Week of Pregnancy

Source: https://www.whattoexpect.com/pregnancy/week-by-week/weeks-1-and-2.aspx

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