Miscarriage in the First Trimester: Common Causes and Prevention

Early pregnancy loss is very common, affecting 1 in every 10 pregnancies. This is diagnostically distinct from a chemical pregnancy, which occurs shortly after implantation and is thought to account for between 50% and 75% of all miscarriages.

In contrast, early pregnancy loss is defined by the absence of an embryo or fetus or a fetus that exhibits no heart activity. Unfortunately, science has yet to uncover a definitive cause of early miscarriage—but it’s thought that several factors, including genetics and preexisting conditions, play a contributing role.

While miscarriage statistics can feel scary, it’s important to remember that around 80% of them occur in the first trimester; you’re unlikely to have one if you and your baby pass the 12-week mark. Learning about symptoms of early pregnancy and existing research in miscarriage can help you shift your focus onto what you can control—setting the stage for a healthy pregnancy journey by getting back to basics.

What causes a miscarriage in your first trimester?

There is no single cause of miscarriage, and most researchers believe pregnancy loss occurs due to a suite of factors.

That said, studies indicate that several health conditions correlate strongly with heightened miscarriage risk, including:

• Chromosomal abnormality – An estimated half of early miscarriages result from a chromosomal abnormality that occur as the embryo develops. This usually results when one or some of the typical 46 chromosomes are not copied or are repeated, though it’s not known why this occurs. However, we do know that these sorts of genetic mistakes are more common among women of advanced maternal age.
• Hormonal imbalances – Lower levels of key reproductive hormones in early pregnancy, particularly progesterone, could jeopardize both maternal and embryonic health. Insufficient progesterone may make the uterus less hospitable to an implanted egg, or cause its premature expulsion from the uterus.
• Having type 1, type 2, or gestational diabetes – Living with diabetes or developing gestational diabetes during pregnancy can cause higher-than-average blood glucose levels, which can put you at a higher risk of miscarriage. Without proper management, diabetes can also increase the probability of stillbirth in later trimesters.
• Infections – Infections in the uterus or cervix may be contracted by the baby and can sometimes result in a type of pregnancy loss known as septic miscarriage. Infections most commonly responsible for pregnancy loss include herpes simplex, listeria, and ureaplasma (rubella).
• Thyroid conditions – Both hyperthyroidism and hypothyroidism can result in an elevated risk of pregnancy loss. This is because a growing fetus relies on its mother’s thyroid hormones until its own thyroid develops and begins functioning.
• Anatomical issues – In some cases, abnormalities in female anatomy, like the uterus and cervix, can make it too difficult for the body to support a successful pregnancy, leading to miscarriage.

Miscarriage Types and Symptoms

Physicians recognize several types of miscarriage among pregnant women:

• Threatened miscarriage – In a threatened miscarriage, a miscarriage has not yet occurred, but you are at elevated risk of having one. Early in pregnancy, threatened miscarriage may be indicated by spotting or light bleeding. Fortunately, only around ⅓ of women who notice bleeding experience pregnancy loss. If you notice these miscarriage symptoms, reach out to your doctor as soon as possible so that they can monitor your fetal health.
• Complete miscarriage – Complete miscarriage refers to a pregnancy loss where both the embryo and the tissue are completely shed from the uterus.
• Incomplete miscarriage – In this type of pregnancy loss, only some of the tissue has exited the uterus. Incomplete miscarriages may resolve on their own, or they may require intervention to help the rest of the tissue pass.
• Anembryonic gestation – This refers to a pregnancy loss where implantation occurred, but the embryo did not progress.
• Embryonic or fetal demise – In this case, implantation occurred successfully but the embryo stopped growing prematurely.

Depending on how far along you are, miscarriage symptoms may vary. Commonly reported ones include:

• Feeling light-headed, dizzy, or faint
• Spotting or light bleeding
• Brown-colored vaginal discharge that resembles coffee grounds
• Cramping or abdominal pains
• Release of tissue or blood clots

Who is at risk of miscarriage?

Unless you undergo an acute trauma or injury, first-trimester miscarriage cannot be caused by physical activities like high-intensity exercise or having sex. However, there are some factors and conditions that seem to put some women at a higher risk of having one, including:

• Maternal age – Miscarriage becomes more likely the older you are. The American College of Obstetricians and Gynecologists (ACOG) reports the following rates of pregnancy loss according to age:
  • Age 35 – 20%
  • Age 40 – 40%
  • Age 45 – 80%
• History of miscarriages – Having a history of miscarriage is the second biggest factor correlating with pregnancy loss: women who’ve already experienced one have a 25% chance of having another. That said, a history of miscarriage by no means bars you from having successful future pregnancy. However, it can indicate that it’s time to get tested for an illness that could make getting pregnant more challenging, like a blood clotting disorder.
• Using substances like tobacco or alcohol – Using alcohol, tobacco, or other psychoactive substances can be hazardous and raise your risk of miscarriage at every stage of pregnancy.
• Weight – Having a higher-than-average BMI or being obese also correlates with an increased risk of miscarriage. This is likely caused by conditions associated with obesity or being overweight, like hypertension or diabetes, which can lead to fetal health complications.

Best Practices for Reducing Risk of Miscarriage

Unfortunately, the ACOG does not recommend any interventions or techniques for decreasing risk of early miscarriage. Many of the factors that can elevate the likelihood of pregnancy loss, like genetics, can’t be prevented or minimized.

With that in mind, the best way to encourage both maternal and fetal health is by taking a holistic approach and focusing on the following building blocks of a healthy pregnancy.

Making Your Prenatal Appointments

In general, a pregnant women is advised to schedule prenatal check-ups in accordance with the following timeline:

• Weeks 4 to 28 – 1 prenatal appointment every 4 weeks (7 appointments total)
• Weeks 28 to 36 – 1 prenatal appointment every 2 weeks (4 appointments total)
• Weeks 36 to 40 – 1 prenatal appointment every week (4 to 5 appointments total)

Understandably, 15 or 16 appointments can feel like a lot to handle, and depending on the condition of your health, you may need to drop into your doctor more. That said, regular check-ups are perhaps the most important feature of miscarriage monitoring, as technologies like fetal ultrasounds can make it easier to track fetal health.

Emphasizing Your Overall Well-Being

When your own body’s needs are fulfilled, your baby has the best possible chances from the get-go. The pillars of prenatal wellness include:

• Nutrition – Taking a prenatal vitamin is an excellent way to incorporate key pregnancy nutrients—like folic acid, calcium, and vitamin D—that promote embryonic and fetal development throughout pregnancy. It’s also best to eliminate or limit exposure to certain foods that may be contaminated with heavy metals or bacteria, like high-mercury seafood and deli meats.
• Daily movement – Incorporating daily movement practices—whether it’s yoga, walking, or even some gentle stretching—can help encourage heart health, lower blood pressure, and moderate weight gain during pregnancy.
• Stress reduction – Stress isn’t considered a direct causal factor in miscarriage, but it has been linked to other maternal and fetal health hazards, like high blood pressure and low birth weight. Whether it’s getting a regular prenatal massage or taking up journaling, try indulging in some soothing activities as your body adjusts to the symptoms of early pregnancy.
• The swapping of substances – If you imbibed alcohol or other substances before pregnancy, it may feel difficult to leave those habits behind—even if it’s for the sake of your baby. Fortunately, there are plenty of ways to get creative and have fun with your substance swaps, like swapping happy hours for trivia nights and taking brisk walks instead of nicotine breaks.

Many expecting moms wonder if caffeine is considered a hazard during pregnancy, and some evidence does suggest that limiting caffeine may help to curb the likelihood of miscarriage. That said, there’s no conclusive connection between caffeine consumption and the risk of miscarriage—so unless you want to play it very safe, there’s nothing wrong with enjoying a daily latte or London fog.

Talking to Your Doctor If You Have a History of Miscarriage

If you’ve experienced a pregnancy loss before, speaking with your healthcare provider can help you assess whether medical intervention can help support a current or planned pregnancy.

Some women with a history of pregnancy loss may be served by progesterone therapy in early pregnancy, which supplements the body with extra progesterone to support and protect a developing fetus.

Encourage a Healthier Pregnancy with SneakPeek

It’s normal to feel concerned for your baby’s health, particularly in those tender weeks of early pregnancy. While miscarriage outcomes are largely out of our hands, separating the myths from the most current research can help encourage confidence and a stress-free path toward parenthood.

Discover more science-backed facts about your future little one with SneakPeek’s at-home Early Gender DNA Test. With this at-home SneaPeek Test, you can learn your baby’s gender as early as 6 weeks with over 99% clinically-proven accurate¹ results. Your results are also physician-reviewed, privacy-protected, and processed the same day we receive your sample.

SneakPeek remains OBGYN’s #1-recommended early gender blood test, with the trust of 1 million moms behind it. For more on what you can learn about your future baby, check out our full collection today.

This post has been reviewed for accuracy by the following medical professional:

Dr. Heather Soper, Certified Nurse Midwife

Dr. Heather Soper brings over 15 years of experience in women's health and obstetrics to her role as the owner of The Genesis Resort for Birth. Complementing her clinical practice, she serves as an Assistant Professor of Nursing at James Madison University, where she educates nursing students with a focus on compassionate, patient-centered care. Her advanced training and dedication to midwifery are evident in her contribution to both academia and the wellness of expectant mothers.

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