Everything a Doctor Wants you to Know About Your First Month of Pregnancy

Last updated: May 28, 2021

Contributed by:
Kate Killoran M.D.
Obstetrics & Gynecology
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Everything a doctor wants you to know about the first month of your pregnancy.


The beginning of a new pregnancy can be an exciting time. Whether the first month of pregnancy goes undetected or each day is celebrated; there are certain things our doctors would love to expect parents to know. 



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While your monthly period may be a sign that you are not with a child; the first day of your last period is actually considered the first day of your pregnancy. This is because the first day of your period is considered day one of your menstrual cycle and we start counting the days of your pregnancy with the first day of your cycle


While day one of your cycles is considered the first day of your period, most women’s fertility window is between days 11 and 21. Thus you will not conceive until ovulation occurs. Women with a typical 28-day cycle ovulate around day 13-14, but are potentially fertile before ovulation because sperm can live inside the body for up to five days. However, it is possible for women with short cycles to actually get pregnant if they have sex on their period! 


When is my due date?

conception is not the start of the first month of pregnancy

Source: Canva


It can be hard to determine your due date for many reasons. First, many women may mistake implantation bleeding (more about that below) for a light period. Secondly, many women do not track their periods and may not remember when their last monthly period began. 



pregnancy conception calculator

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In addition, many women’s menstrual cycles are not exactly 28 days. You can ovulate sooner or later in your cycle, which would cause your dates to be off. 


The most accurate way to date a pregnancy is to get a dating ultrasound. In Canada, The Society of Obstetricians and Gynecologists of Canada recommends that all pregnant women have a dating ultrasound between 11-14 weeks and one anatomic ultrasound between 18-20 weeks. 


Unfortunately, at one month pregnant, you are not yet due for your first ultrasound to get an accurate reading of how long you have been pregnant. 


Talk to a doctor online about ovulation


Nine Months of Fun?

Pregnancy is often believed to be ‘9 months’ but it is actually 40 weeks. Calendar months are varying numbers of days, so your pregnancy will be measured in weeks. 


While your due date is an estimated day when your baby may come, it is not set in stone. Approximately 60% of babies are born on or before their due date. 


According to ACOG term pregnancy is 38 completed weeks of pregnancy or what I consider 39 weeks. Babies born between 37 0/7 weeks and 38 6/7 weeks are considered early term. Babies born before 37 0/7 weeks are considered preterm.


In 35% of women contractions will begin on their own within two weeks of their due date. Some babies will need to be induced. It is not known why babies become overdue, although it is believed that genetics may play a role. Women who have had a pregnancy go past their due date are more likely to have a future pregnancy go past their due date. 


Related: What is a cryptic pregnancy? 


Your Body During the First Month of Pregnancy

First month of pregnancy

Source: Canva



Just like every baby is unique, so is every pregnancy. Some women may experience symptoms soon after conception, other pregnancies can be asymptomatic. 


Implantation bleeding: Some women may experience spotting or light bleeding approximately 10 to 14 days after conception. This is generally believed to be caused by the fertilized egg attaching itself to the lining of the uterus. 


The bleeding occurs around the time that your regular menstrual period should occur. Some women could mistake the implantation for a light period. However, there are a few differences. Your menstrual period will last several days-usually between two and seven- and will be enough to fill a menstrual pad, cup or tampon every few hours. 


Implantation bleeding is light, stops on its own and doesn’t require any treatment. Some women can mistake implantation bleeding for a light period, which can lead to inaccuracies in determining your due date. 


In addition to implantation bleeding, during your first month of pregnancy you may experience: 


  • Mood changes
  • Bloating
  • Cramps
  • Lower backache
  • Spotting
  • Frequent urination
  • Sore or tender breasts
  • Fatigue
  • Nausea
  • Constipation
  • Food cravings and aversions
  • Missed period.


Even with a planned pregnancy, you may experience feelings of anxiety, stress and sadness. A new baby brings a change to your family dynamic and it is normal to have mixed feelings. Don’t be afraid to reach out to your partner, friends and family for reassurance about this very normal and common occurrence. 

Your Baby’s Development During the First Month of Pregnancy



Before you have missed your monthly period during the first month of pregnancy, your baby already has all the genetic markers to determine its hair color, eye color,height, skin tone and even its fingerprints! 


The first month of pregnancy often goes undetected, but it is very important for your baby’s development. 


Your pregnancy begins after conception as the fertilized egg travels from the fallopian tube and implants itself into the uterine lining. You may or may not experience light bleeding at this time or simply notice the absence of your period. 


embryo forms during the first month of pregnancy

Source: Canva


The egg will begin to divide into a bunch of cells and become an embryo. By the end of month one it will be 10,000 times bigger than it was at conception. 


During the first month the placenta (also called the afterbirth) will begin to form. The placenta is an organ that forms in the uterus along with your growing baby. It provides nutrients and oxygen to your developing baby as well as removing waste from your baby’s blood. 


The placenta attaches to the wall of your uterus and connects to your baby by the umbilical cord. This is the cord that will be cut after your baby is born. After you birth your baby, you will deliver the placenta. 


Your Doctor’s Visits During your First Month of Pregnancy


In fact, if you are planning on getting pregnant, many doctors recommend coming in for a pre-pregnancy health check. They can check for any health conditions that may interfere with a healthy pregnancy. 


Pregnancy Test

sexually transmitted infections can cause bleeding after sex while pregnant

Source: Canva


The prepregnancy check is very similar to your first doctor’s appointment once you discover you are pregnant. The main difference is that your first doctor’s appointment after a positive pregnancy test your doctor will confirm your pregnancy. Your doctor will do this by measuring the amount of a hormone called human chorionic gonadotropin (hCG). This hormone is what is measured using a home pregnancy test using your urine. Your doctor may confirm your pregnancy through a urine test or a blood test. Often, your first appointment once pregnant is not until the second or third month. If that is the case a confirmatory pregnancy test is not usually necessary. 


Additional Tests


There are many tests that your doctor will likely perform during a pre-pregnancy visit or first visit during your pregnancy. 


Pap Smear

heavy or prolonged menstrual bleeding may be evaluated with a pelvic exam

Source: Canva


If you haven’t had a recent pap smear, it is important to get this done prior to becoming pregnant if possible. This is because abnormal pap results can require additional follow-up. This might include a biopsy which can cause cramping and bleeding, two symptoms most pregnant women do not want to see. 




In addition, your doctor will conduct screenings for STI/STDs. No matter how monogamous your relationship is, it is still important to have these tests done. This is because many STIs, such as chlamydia and HPV can be asymptomatic for months or even years. These infections can be passed along to your baby and need to be identified and treated. 


Glucose Test


Your healthcare provider may do a glucose test to pinpoint any potential health problems due to being diabetic or prediabetic. If this test is done pre-pregnancy, your doctor can help you to get this condition under control prior to becoming pregnant. 


This test is not usually done until much later in pregnancy unless you are considered high risk for diabetes, which would include a history of gestational diabetes in the past or if you are obese. If this condition is discovered after pregnancy, your doctor can help you manage your diabetes during your pregnancy. If the symptoms are not managed properly your baby could have low blood sugar after birth or experience excessive fetal growth. 


Thyroid Test

A pre-pregnancy thyroid test is important to ensure proper fetus development. If you do have thyroid disease, the fetus could have growth issues. Ensure your thyroid function is good and also talk to a doctor about thyroid issues for your health, and your baby’s as well.


Genetic Screening

a blood test is an important pre-pregnancy test

Source: Canva


According to the American College of Obstetricians and Gynecologists all expecting parents should be offered genetic screening or testing depending on if they are planning to become pregnant or already pregnant. This testing should be offered regardless of ethnicity. 


The pre-pregnancy screening can look for genetic disorders such as Cystic fibrosis, sickle trait, Tay-Sachs disease, and others that should all be rooted out. 


In addition, there should be a complete blood count and screening for thalassemias and hemoglobinopathies.

Screening for Tay-Sachs and other mutations has traditionally been based on ethnicity, primarily Ashkenazi Jewish. Due to our increasing multicultural background, some OB/GYNs are offering screening to all.


Lifestyle Choices

Source: Canva


In addition to confirming your pregnancy, your doctor will also advise you of the best possible lifestyle choices to ensure a healthier pregnancy. 


Smoking, drinking and doing recreational drugs can have a negative impact on your baby’s development. This is especially true during the first trimester. If you are a smoker, you can speak to your doctor on how best to minimize its possible negative impacts on your pregnancy. 


Your doctor may also speak to you about your nutrition. Folic acid is important to your body, especially during the first trimester. If you are planning to become pregnant, your doctor may prescribe a prenatal vitamin that includes folic acid. 


The Center for Disease Control (CDC) recommends that all women, during their reproductive years, take 400 micrograms (mcg) of folic acid each day, in addition to consuming food folate from a varied diet. This helps prevent some major birth defects of the baby’s brain (anencephaly) and spine (spina bifida).


Related: Signs Labor is Near

Healthy Weight


Starting your pregnancy at a healthy weight is ideal. Obesity during pregnancy can cause health issues for you and your baby. Any body mass index between 25.1 and 29.9 is considered overweight. A body mass index over 30 is considered obese. 


Obesity can increase the risk of several pregnancy complications including: 


  • Miscarriage
  • Birth Defects-including neural tube defects and heart defects. 
  • Ultrasound difficulty-having too much body fat can make getting an accurate anatomy scan difficult 
  • Excessive fetal growth during pregnancy also known as macrosomia. This can result in the baby getting injured during birth. 
  • Increased risk of cesarean section due to macrosomia or other pregnancy complications.
  • Preterm birth-obesity-related health issues, such as pre-eclampsia can cause your baby to be born early.
  • Stillbirth-the higher your BMI, the greater the risk of stillbirth. 





Source: Canva

Exercise is not only safe but encouraged during pregancy. You and your healthcare provider can discuss how to exercise safely during pregnancy. 


Check out 5 exercises you can do during pregnancy to help with labor. 


Warning Signs


Your doctor can also advise you of any symptoms that could require medical attention. Up to 25% of women have some bleeding during the first trimester of pregnancy. Of these women, 50% will not have a miscarriage. 


Vaginal bleeding is more common in women who have had a baby before than women who are pregnant for the first time. 


Questions about Your Pregnancy?


Pregnancy is a time where you are full of questions. Keep a doctor in your pocket with Your Doctors Online. You can connect with a doctor 24 hours a day to answer all your questions and concerns within minutes. Lose the stress and gain the insights of our licensed doctors


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Disclaimer: This article provides general information and is not intended to diagnose, treat or cure any disease or medical condition. If you require specific advice, please consult one of our medical professionals through the app. However, in case of an emergency, please call 911.

About Kate Killoran M.D.

Dr. Kate Killoran has been a practising OB/GYN for almost 20 years. She graduated from the Boston School of Medicine and completed her residency at the University of Colorado. Dr. Killoran understands the importance of wellness. She credits surviving breast cancer with her renewed focus on her own health. Along with a busy obstetrics practice, she is also a health coach and recently completed the Ironman Half Triathalon. She lives happily with her family in Maine and connects with women around the world via her blog and her work with Your Doctors Online.

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