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By the third week of pregnancy, if you did ovulate, and the egg met the sperm, you are formally pregnant..

James W. Brann, MD

Your Pregnancy MD
Pregnancy Week Three

Author James W. Brann, M.D.

Ovulation last week, are you pregnant this week?
Ovulation last week, are you pregnant?

By the third week of pregnancy, you likely ovulated last week. If you did ovulated, and the egg met the sperm, you are formally pregnant. Congratulations! Many women don’t realize that they’ve conceived until next week – when they miss their period.

By the third week of pregnancy your egg met a sperm. Congratulations! You are pregnant.
Sperm meets egg at 3 weeks.

Amazing things are taking place inside your womb this week. At the beginning of pregnancy week 3, the fertilized egg is one single cell (zygote). Four days after fertilization, the egg will divide into a ball of 58 cells. By the end of the week, the ball of cells will divide into 150 cells, known as a blastocyst. The blastocyst will be making its way into your uterus, where it will imbed itself and your baby will grow for the next nine months.

It may be too early to take a home pregnancy test this week, it may give you a negative result. The level of the pregnancy hormone, human chorionic gonadotropin (hCG) may not be high enough yet. After implantation, the level of hCG will quickly increase, doubling its amount every few days. So, if you first test negative with a home pregnancy test, wait a few days and try again.

The Business of Conception:
Sperm Meets Egg

Pregnancy isn’t possible without conception – an intricate and complex process that involves the release of an egg from the woman’s ovary, fertilization by the man’s sperm, and implantation in the lining of her uterus. Conception is a beautiful process that joins one egg to one single sperm cell to create life.

The Release of an Egg (Ovulation)

By the third week of pregnancy your egg is surrounded by sperm.
Ovum or Egg

Conception begins with ovulation – the release of a mature egg from one of your ovaries. Immediately after the egg ruptures from its follicle, it is literally brushed into the fallopian tube by the fimbriae (the tiny finger-like ends of the fallopian tube). The egg travels down the fallopian tube in the direction of the uterus. The journey from ovary to the uterus can take five days, but during the course of this time, the egg will be fertilized by the sperm. If the egg isn’t fertilized within 12 to 24 hours after ovulation, it will dissolve and you’ve missed your chance of pregnancy for that month. At the same time that the egg is making its way through the fallopian tube, the ruptured follicle transforms into a structure called the corpus luteum, which begins to secret progesterone and estrogen. Both of these hormones start to thicken the lining of the uterus, in preparation for implantation.

The Sperm’s Long Swim

Each sperm has an oval head and a long tail, which propels it towards the unfertilized egg.
Sperm in Fallopian Tube

After each ejaculation, a fertile man will release between 20 million to 250 million sperm into a woman’s vagina. Each sperm has an oval head and a long tail, which work as a team to propel it towards the fallopian tube, where the unfertilized egg is waiting. The journey from the vagina to the fallopian tube may take 45 minutes for the fastest swimmers, and up to 12 hours for the slow sperm. If you haven’t ovulated yet, sperm can stay alive in your reproductive tract for three to five days.

Although your partner will release millions of sperm, only a few hundred will actually make its way to the fallopian tube. Some will die in your vagina – which is acidic and deadly to sperm. Others get caught in your cervical mucus, which can act like an impassable barrier in which sperm cannot swim through. It’s only during the one or two days that you’re most fertile that the cervical mucus becomes more receptive to allowing the strongest swimmers to enter the uterus. But even after entering, these strong sperm still have to travel roughly seven inches from the cervix, through the uterus, up to the fallopian tubes. Some sperm will get lost or die along the way. Of the 200 that survive, they all must fight each other to penetrate the egg’s outer shell.

Fertilization – The Moment of Conception

All of the sperm will cluster around the egg and attempt to penetrate its tough outer layer. Each works frantically to beat the others and get inside. The strongest of the bunch will succeed and fertilize the egg. Once this happens, the outside of the egg automatically thickens so that no other sperm can enter. It becomes like a protective shield that keeps out the competitors, so that your future baby is the result of only one sperm and one egg.

Within 24 hours after sperm and egg meet, the egg will be fertilized. Genetic material from the sperm and the genetic material from the egg will create a new single cell, called a zygote, which starts to divide very quickly. The fertilized egg is now a bundle of cells.

{Helpful Tip} At this point, your baby’s gender has already been determined. If a sperm with a Y chromosome fertilized the egg, you will end up with a little boy. If the lucky sperm had an X chromosome, you will end up with a little girl.

The ball of cells makes its way down the fallopian tube and enters the uterus. This journey takes three to four days. In rare circumstances, the ball of cells will stay in the fallopian tube. The pregnancy that results is called an ectopic pregnancy (or a tubal pregnancy), and it’s a dangerous pregnancy complication if left untreated.

Within a week of fertilization, the newly forming embryo will trigger the pituitary gland by producing a pregnancy hormone called human chorionic gonadotrophin (hCG), which turns off your menstrual cycle. This hormone also keeps the levels of progesterone in your body high to support your pregnancy. 

Implantation – You’re Officially Pregnant!

Once the ball of cells (called a blastocyst at this point) arrives in your uterus, it will attach itself to the surface lining of your uterus. At this early stage in fetal development, the blastocyst produces enzymes that allow it to dig its way deeper into the uterine lining, where it will lie safely beneath the surface. During implantation, a chemical exchange also takes place between the blastocyst and your body to signal the presence of this new life. This exchange temporarily suppresses your immune system so that it cannot create antibodies that may attack the blastocyst as foreign matter.

Once the blastocyst embeds itself firmly and permanently, you are officially pregnant – though you won’t know it for another week or so. After implantation, some cells of the blastocyst will eventually become the placenta and others will become the embryo (your future baby).

What’s Happening Inside Your Body

During pregnancy week 3, life-changing events are taking place in your womb. Your future baby is only a ball of cells at this point, but the ball of cells (the blastocyst) is multiplying rapidly. In the beginning, the blastocyst is made of two distinct layers of cells – the trophoblast (the outer later of cells) and the inner cell mass. The trophoblast burrows into your uterine wall during implantation, and it will eventually develop into the baby’s placenta. The inner cell mass forms the embryo (your future baby).

After implantation, the trophoblast begins to produce a pregnancy hormone called human chorionic gonadotrophin (hCG), which prevents your ovaries from releasing any more eggs and forces them to increase production of the hormones, estrogen and progesterone. These two hormones will prevent your uterus from shedding its lining (and your newly created baby).

At 3 weeks pregnant, some of the cells of the trophoblast begin to form an outer layer of membranes (called the chorion), which surrounds the new embryo. The inner layer of membranes (called the amnion) starts to form between 10 to 12 days after fertilization (between pregnancy week 3 and 4). The amnion forms the amniotic sac – which fills with amniotic fluid and starts to envelop the developing baby. The amniotic sac will cushion and protect your unborn baby from any harm for the next 37 weeks.

During this early week of pregnancy, your new baby is receiving his or her supply of oxygen and nutrients from a very rudimentary circulation system, which is comprised of miniscule channels that connect your future child to the blood vessels in the wall of your uterus. This role will be taken over by the newly developed placenta at the end of pregnancy week 4. Because your baby is microscopic at this point and you haven’t missed your period yet, you won’t realize that you’re pregnant. For most women, the levels of hCG in their urine aren’t high enough to be detected by a home pregnancy test. You will have to wait until the day of your missed period before you can take a home pregnancy test and get an accurate result. (Keep in mind – despite product claims, most home pregnancy tests are not sensitive enough to detect early pregnancy until the week after your missed period. If you test negative at first, wait an additional week and test again.)

Conception While Using Birth Control

No birth control method is 100 percent effective at preventing pregnancy. Out of all birth control types, the intrauterine device (IUD) is more than 99 percent effective, and one of the best ways to prevent pregnancy. Hormonal contraceptives can be 99 percent effective if used properly and consistently. This includes birth control pills, the birth control patch (OrthoEvra), the birth control ring (NuvaRing), and birth control injections (Depo-Provera). Male condoms are 94 to 97 percent effective; the female condom is less effective than that.

Why is Pregnancy Possible on Birth Control?

Birth control is safe and effective when you use it consistently and according to package instructions. In a majority of birth control failures, it’s due to user failure. For condom users, this means the condom was put on wrong, or it breaks during sex. The NuvaRing and diaphragm can also inserted wrong, and this puts you at risk for pregnancy. Pregnancy may be possible with the intrauterine device (IUD) if the IUD is expelled from the uterus without you realizing it. 

If you receive the Depo-Provera shot, you must remember to schedule your injection every 12 weeks, or you’ll be at risk for pregnancy. You can also get pregnant while using the OrthoEvra patch if you don’t apply it on the skin on time. (The patch is also less effective in women who are less than 198 pounds). 

Women who are on the birth control pill can get pregnant when they forget to take a pill. Pregnancy on the pill can also occur if the hormones in the pill aren’t absorbed into your system properly – due to vomiting or drug interactions with other medications you’re taking. Neurological medication, like seizure medicine, and antibiotics can often reduce the effectiveness of the pill. Alcohol can also make your birth control pill less effective at preventing pregnancy.

Some studies have suggested that being overweight can increase your risk of getting pregnant while on the pill, while other studies have found a weak correlation. Because of this, researchers cannot come to a consensus on whether your body weight affects the pill’s effectiveness. If you end up getting pregnant on the pill (or another form of hormonal contraceptive), but you’re unaware of the pregnancy for a while, don’t worry. Inadvertent pill taking during early pregnancy has not been linked to any birth defects.

{Helpful Tip} Although the birth control pill is 99 percent effective, it is most effective if you take it every day around the same time. Forgetting to take your birth control pill on a regular basis is the biggest reason for its unexpected pregnancy while on the pill. If you miss a pill, you should always use a backup method of birth control, like condoms or spermicides.

The Danger of IUDs and Unexpected Pregnancies

The only birth control method that can complicate an unplanned pregnancy is the intrauterine device (IUD). Although the failure rate of an IUD is less than 1 percent, pregnancy does happen. Women who conceive with an IUD in place have a miscarriage risk of 40 to 50 percent – this is more than double the normal miscarriage risk. You can greatly reduce the risk of miscarriage by removing the IUD as soon as possible. Women who get pregnant with an IUD are also at risk for ectopic pregnancy.

If the IUD still remains in place during the second trimester of pregnancy, the woman has a fourfold risk of experiencing preterm labor and delivery and having a late miscarriage or stillborn. There’s no increased risk of birth defects if you conceive with an IUD.

How Twins are Conceived

In the United States, 1 in 32 births result in twins. The rate of twin births has increased 70 percent since 1980s, and it is mostly due to more and more women taking fertility drugs and using assisted reproductive technologies (like in vitro fertilization, or IVF) to help them conceive. A majority of the twins born today are fraternal twins. The rate of identical twins is one in 250 – which is roughly the same statistic since the 1980s. Identical and fraternal (non-identical) twin pregnancies accounts for over 90 percent of all multiple births.

Conception of Identical Twins

Identical twins (also called monozygotic twins) develop when one fertilized egg (a single zygote) splits into two separate embryos. This occurs within the first 12 days after fertilization. Experts believe that identical twins occur by chance, and unlike with fraternal twins, it’s not influenced by your age, race, or family history.

Because of how identical twins develop, they share the same genome (genes). They have the same blood type, and a majority of them have the same hair color, skin color, and eye color. They look very similar to each other, but many have different personalities. Despite common belief, identical twins don’t always look exactly the same. In some cases, environmental influences can change the appearance of twins. Identical twins are always the same gender. Identical twins do not share the same fingerprints.

In a majority of cases (70 percent), identical twins will share the same placenta. Each baby will have his or her own umbilical cord. Most identical twins will develop in two separate amniotic sacs. In rare cases, twins can share the same amniotic sac.

Monozygotic twins – identical twins – are less common than fraternal twins, but this type of twin can occur in triplet, quadruplet, and higher multiple pregnancies as well.

Conception of Fraternal Twins

Fraternal twins (also called dizygotic twins, and sometimes non-identical twins) occur when a woman releases two eggs at ovulation, and different sperm fertilizes each egg. Because of this, fraternal twins are no more alike than other siblings. They just happened to be conceived at the same time. They do not share genetic material, since they do not come from the same egg.

Non-identical twins can look similar, especially if they are the same gender, but many look very different. They can be different genders (one girl and one boy, or two of the same sex). They can have different blood types, and their eyes, hair, and skin color aren’t always the same.

There is a genetic component to fraternal twins; they tend to run in families. If someone in your family gave birth to fraternal twins, you’re at higher risk of having them. Other risk factors for fraternal twins include advanced maternal age (you’re over 35); you’re African-American; and using fertility drugs or assisted reproductive technologies (like in vitro fertilization).

Pregnant and Plus Size

Tips for a Healthy Pregnancy

If you’re overweight and newly pregnant, you probably want to have the healthiest pregnancy possible. Although being plus-sized does put you at risk for certain pregnancy complications, your weight doesn’t automatically doom your pregnancy. There are many overweight and plus-sized pregnant women who have normal pregnancies and healthy babies. It is possible for overweight moms-to-be to have healthy pregnancies. You can overcome the statistics by eating a healthy and balanced diet, exercising regularly in pregnancy, and staying within the recommended weight gain guidelines for your body size.

Pregnancy Complications When You’re Plus Sized

When you’re overweight, you are at higher risk for pregnancy complications. Keep in mind that just because you’re in the higher risk group, this does not automatically mean that you will experience obstetric complications. You can minimize your potential risk with lifestyle modifications.

Obesity in pregnancy puts you at risk for the following complications:

Gestational Hypertension – High blood pressure is a common pregnancy complication that can affect overweight women. Research studies have indicated that 10 percent of obese women (who have body mass indexes of 30 or above) will experience high blood pressure in pregnancy.

You will be diagnosed with gestational hypertension if you have high blood pressure (140 over 90 or higher) after 20 weeks pregnant, but there is no protein in your urine. Gestational hypertension can increase your risk of preeclampsia (a more severe form of high blood pressure in pregnancy), intrauterine growth restriction (your baby doesn’t grow properly in the womb), preterm birth (delivering a baby before 37 weeks pregnant), placental abruption (a serious complication in which the placenta separates from the uterus before your baby is ready to be born), and stillbirths (your baby dies in the womb).

If you develop gestational hypertension, don’t freak out. There are ways to manage high blood pressure in pregnancy. At every prenatal visit – make sure you show up to each one, especially if you’re having complications – your healthcare provider will take your blood pressure. You may be placed on some degree of bed rest and prescribed medication to lower your blood pressure.

Preeclampsia – If you develop high blood pressure in pregnancy, and the doctor finds protein in your urine, you will be diagnosed with a complication called preeclampsia. The severity of this complication can range from mild to severe. In the most severe cases, you can start to have seizures – this condition is called eclampsia. Women with severe cases of preeclampsia may also have organ failure, placental abruption, poor fetal growth, and decreased amniotic fluid.

Being overweight can increase your risk for developing preeclampsia. Clinical studies have found that 9 to 12 percent of plus-sized pregnant women will develop preeclampsia. (This is compared to 4 to 5 percent of women with a normal BMI range.)

To manage mild cases of preeclampsia, you may be asked to stay on bed rest, perform daily fetal kick counts, and pay attention to your symptoms. Severe cases of preeclampsia will require you to stay in the hospital, where your pregnancy will be monitored. You may also be given medication to lower your blood pressure. You also may be induced to protect your health and the health of your baby.

Gestational Diabetes – Roughly six percent of overweight women will develop diabetes (high blood sugar) in pregnancy. (This is compared to 2 percent of women with a normal BMI.) Uncontrolled diabetes can lead macrosomia – an overly large baby. Your baby may be too large to go through the birth canal, and this can lead to problems during delivery. Shortly after birth, your newborn may experience low blood sugar and he or she may also suffer from breathing problems at birth. There have been several studies that have linked severe gestational diabetes with an increased risk of stillbirth in the last trimester. Gestational diabetes also increases your risk of developing preeclampsia.

Fortunately, gestational diabetes can be controlled with eating a well-planned diet, moderate exercise, and insulin injections (if exercise and diet aren’t enough).

Neural Tube Defects – Plus sized pregnant women have a higher risk of having a baby with neural tube defects (which are birth defects of the brain and spinal cord). Researchers aren’t sure why overweight women are more at risk for this birth defect, but it’s believed that they have lower blood folate levels than average-sized woman. (Folic acid has been linked to preventing neural tube defects from occurring.) For this reason, it’s highly recommended that overweight and obese women start to take folic acid supplements one month before and throughout their pregnancy. Because obese women are at higher risk for neural tube defects, it doesn’t hurt for them to take 1,000 micrograms of folic acid to reduce their risk.

Big Babies – Although many overweight women can have average-sized babies, being plus-sized can put you at risk for giving birth to an overly large baby (over 9 pounds, 15 pounces). Women who have undiagnosed or uncontrolled gestational diabetes, women with a family history of large babies, and women who go past their due date are more likely to give birth to big babies.  

When you have a big baby, you’re at increased risk of a long and arduous labor. If you opt to have a vaginal delivery, you’re more likely to experience perineal tearing, increased blood loss, and bruise or break your tailbone. There’s also a chance that your baby’s shoulder will get stuck behind your pubic bone (a complication called shoulder dystocia). Because of all these risks, having a big baby increases the likelihood of a cesarean delivery (C-section).

If your healthcare practitioner believes that your baby may be large, you should discuss your labor and delivery options with him or her. Some physicians may recommend that you have a C-section, but others may allow you to have a trial of labor, in which you attempt to have a vaginal delivery.

Longer, More Difficult Labor – When you’re overweight, you may face a longer, more difficult vaginal delivery. According to a 2004 research study, published in the journal, Obstetrics and Gynecology, overweight women are in active labor for 80 minutes longer than their skinner counterparts. Obese women will have in active labor for 105 minutes longer. (Active labor is the stage of labor in which your cervix dilates from four to ten centimeters.)

To reduce your chance of having a longer labor, you can exercise regularly (if your doctor says it’s OK and you’re not having any other complications), eat a healthy diet, and gain the ideal amount of weight for your body size. Cesarean Delivery – Along with a longer labor, plus-sized pregnant women are at higher risk of giving birth via C-section. Several research studies have indicated that 26 to 35 percent of overweight and obese pregnant women will have a C-section (compared to 20 percent of women with a normal BMI). This increased likelihood of C-section is often due to the other complications (like preeclampsia, gestational diabetes, and other health problems) that plus-sized moms-to-be are at risk for.

Tips to Reduce Your Risk of Complications:

Although all of the pregnancy complications associated with obesity can be frightening, most of them are manageable. There are also several ways that you can reduce your risk and improve your chances of having a normal, healthy pregnancy without any problems.

Gain the Recommended Weight for Your Body Size – If you are overweight (with a BMI between 25 and 29.9), it’s recommended that you gain between 15 to 25 pounds by the end of your pregnancy. Overweight women (with a BMI of over 30) should gain less than this – only 11 to 20 pounds by the time they deliver. When you gain more than your recommended weight, you’re 50 times more likely to develop gestational diabetes and other complications.  

Don’t Diet – Although it may be tempting to try to shed a few pounds, pregnancy is not the time for you to diet. Restricting your diet can deprive your unborn baby of the nutrients and vitamins that he or she needs to develop properly. Don’t cut back on calories and limit nutrients for your growing baby. Eat healthy, but don’t literally “eat for two.” Overeating can make you gain too much weight.

Moderate Exercise on Most Days of the Week – To help you stay within the recommended weight gain for your body size, you should exercise regularly. A daily 30 or 40-minute walk can go a long way in helping you minimizing your risk of complications. Don’t overdo it with the exercise, especially if you haven’t exercised before. Walking, swimming, prenatal yoga, prenatal Pilates, and low-impact aerobics are all wonderful ways for you to exercise and stay fit in pregnancy.

Commonly Asked Questions – Week 3

The most common asked questions during week 3
Commonly asked questions of week 3

Q. How accurate are home pregnancy tests?

A. Home pregnancy tests can be quite accurate. Although some products claim that they’re over 99 percent accurate and that you can use them on the first day of your missed period, this isn’t always true. Some brands are more sensitive at detecting the presence of human chorionic gonadotrophin (hCG) – the pregnancy hormone produced by the cells of the placenta – in your urine.

To check for the sensitivity of the home pregnancy test you’ve bought, you can check the package inserts, which sometimes report the lowest concentration of hCG that the test detects. As a rule of thumb, the lower the number, the more sensitive the test. For instance, a home pregnancy test that can detect hCG at 20 mIU/ml is more sensitive than one that says 50 mIU/ml.

Most home pregnancy tests on the market can’t accurately detect pregnancy on the day of your missed period. You will get the most accurate results the week after your expected period. You can also boost the accuracy of the home pregnancy test by testing your urine in the morning, when you first empty your bladder.

Q. My husband and I have been trying to have a baby for months now. We always have sex around my fertile time, but I’m still not pregnant. Why can’t I conceive?

A. Conception is a complicated process, and it’s not always easy for every woman. For you to successfully conceive, several things have to fall into place. For one, you must have a healthy reproductive system. Your hormones should be balanced to foster the development of your egg in the ovary. Second, you have to ovulate that month. If you don’t ovulate, there’s no egg for your husband’s sperm to fertilize. Third, you need to have sex at the right time in your menstrual cycle. Although you may think that you’re having sex during your fertile time, it’s possible that stress or other lifestyle factors caused you to have delayed ovulation. If your timing is off, it’s unlikely that your egg and sperm will meet. Fourth, your husband needs to produce plenty of healthy sperm that are strong enough to swim past your cervical mucus and reach your egg.

It’s also possible that your egg was fertilized, but for some reason, implantation did not take place that month. In order for you to become pregnant, the blastocyst must implant securely in the wall of your uterus. Sometimes, there was a chromosomal problem with the fertilized egg, and you had a very early miscarriage and didn’t realize it. The “menstrual blood” that you experienced after that miscarriage was actually a failed pregnancy.

So you see – lots of things can go wrong when it comes to conception. Be patient, and you’ll soon get pregnant. If you haven’t conceived within a year, you may want to contact a doctor to help you get down to the root of the problem.

Q. What are the early signs of pregnancy?

A. During pregnancy week 3, you haven’t missed your period, and it’s often too early for you to notice any signs of pregnancy. Next week, you’ll want to pay close attention to any subtle symptoms you may experience. A missed or delayed period is often the first sign that you’re pregnant. If you always have regular periods and never, ever miss a month, you’ll want to take a home pregnancy test and confirm your pregnancy.

Morning sickness is another early sign of pregnancy. You can begin to feel nauseous as early as two weeks after conception. This pregnancy symptom is the result of rapidly rising hormones in the first trimester. Fortunately, your symptoms should abate by the second trimester.

Tender breasts, fatigue, and frequent urination are other early signs of pregnancy. You may start to notice these symptoms as early as three weeks pregnant, and it can be difficult to distinguish these symptoms from normal PMS. This is the reason you’ll want to take a home pregnancy test if you think you might be pregnant.

Q. I’m having some abdominal cramping and discomfort. Is this implantation pain? Am I pregnant?

A. At 3 weeks pregnant, it’s possible that the mild abdominal cramping and discomfort that you’re experiencing is implantation pain. When the fertilized embryo embeds itself into your uterine wall, it’s common for pregnant women to notice some cramping, and they may even notice light spotting or staining. Implantation bleeding shouldn’t be bright red or heavy similar to bleeding with a normal period.

You may notice implantation cramping and pain between five to twelve days after you ovulate. The cramping and discomfort that you feel should be mild and only last one or two days. If your pain is severe, you should call your doctor right away. If you are experiencing severe abdominal pain – it is possible you have an ectopic pregnancy.

Q. I think I might be pregnant, but I had a few alcoholic drinks before I started noticing pregnancy symptoms. Did I accidentally harm my baby?

A. Try not to worry. Your baby is likely perfectly healthy, and the alcoholic drinks that you consumed did not affect his or her development at all. There is no safe level of alcohol consumption in pregnancy, but you should stop drinking alcohol the moment you plan to become pregnant.

Alcohol consumption in pregnancy can cause physical and mental birth defects. Because your baby is undergoing major developmental changes in the first few weeks of pregnancy, it’s vital that you don’t consume anything that could harm him or her. When a pregnant woman drinks, the alcohol passes through her placenta to her baby. Because a baby has an immature body, he or she cannot break it down. This can lead to lifelong permanent damage. Although the few drinks that you had before you realized you might be pregnant probably won’t harm your child, stopping alcohol consumption now will go along way in ensuring you have a healthy, happy pregnancy.


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