How to Keep Your Unborn Baby Healthy

Environmental factors and genetics can be responsible for birth defects

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Birth defects can influence how a newborn looks, functions, or both. In the United States, one of 33 babies is born with a birth defect. Some conditions are readily noticeable, such as cleft lip or palate. Others require special diagnostic tests to visualize, such as congenital heart defects.

Birth defects occur while the baby is developing in the womb. Certain chemicals, medicines, and drugs—called teratogens—can increase the risk of birth defects. During the first 14 days of pregnancy, teratogens either cause no defects or result in miscarriage; this is an all-or-nothing period.

Between 15 and 60 days of gestation (during the first trimester), major organs develop. The fetus is most susceptible to the effects of teratogens, and severe birth defects can result. Teratogens are not the only cause of birth defects. Genetics also play a role. Furthermore, teratogens and genetics can cause damage together.

There’s no sure-fire way of preventing birth defects. Ultimately, environmental and genetic factors conflate to result in these problems. But maintaining a healthy lifestyle, including regular appointments with your OB-GYN before and during pregnancy, can help you have a healthy baby.

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What Do You Have to Give Up While Pregnant?

Alcohol During Pregnancy

Alcohol is a leading cause of birth defects during pregnancy. According to the Centers for Disease Control and Prevention (CDC), there is no known safe amount of alcohol use during pregnancy or while trying to get pregnant. There is also no safe time during pregnancy to drink. All types of alcohol are equally potentially harmful, including all wines and beer.

When a pregnant person drinks alcohol, so does their baby. Furthermore, half of all pregnancies in the United States are unplanned. It can take between four and six weeks before a person knows if they are pregnant. During this period, alcohol could interfere with fetal development. Consumption of alcohol during pregnancy can lead to fetal alcohol syndrome (FAS).

Researchers have not determined minimal limits of alcohol as it relates to FAS. Abnormalities associated with FAS include:

  • Heart, kidney, or bone defects
  • Flattened face secondary to the underdeveloped mid-face
  • Intellectual disability
  • Intrauterine growth restriction (poor growth of the baby while in the womb)
  • Vision and hearing problems
  • Microcephaly (small head and impaired brain development)
  • Poor coordination

The exact means by which alcohol causes FAS are unknown. We do know that alcohol readily crosses the placenta into the fetus’s blood. In the unborn baby’s blood, alcohol reaches concentrations comparable with those observed in the gestational parent's blood.

However, fetuses lack the enzyme needed to break down alcohol. Instead, babies rely on placental and maternal enzymes to clear alcohol. These enzymes aren’t nearly as effective, so plenty of alcohol remains in fetal circulation.

Alcohol may cause substantial damage to the nervous system of the baby. It not only impairs the development of nerve cells but also kills them (a process called apoptosis).

Smoking During Pregnancy

It’s best to quit smoking before getting pregnant; however, for an expectant parent who is still smoking, it’s never too late to quit. Moreover, pregnant people should stay away from second-hand smoke.

A baby born to a parent who smokes during pregnancy may experience:

  • Cleft lip
  • Cleft palate
  • Intrauterine growth restriction
  • Stillbirth
  • Preterm labor
  • SIDS
  • Tremors

Nicotine is 15% more concentrated in the blood of the fetus than in that of the gestational parent. The more heavily that a parent smokes, the greater the risk of intrauterine growth restriction. Furthermore, even those who smoke 10 cigarettes or fewer per day (light smokers) put their babies at twice the risk for low birth weight. The effects of vaping on pregnancy are potentially harmful as well.

Marijuana or Other Recreational Drugs

Marijuana is the most commonly used recreational drug. It is now legal in certain states, which has lots of pregnancy experts concerned.

Some experts believe that marijuana isn’t teratogenic and doesn’t cause birth defects. However, the CDC recommends against pregnant people smoking or using other illicit drugs because these drugs may lead to preterm delivery, low birth weight, and birth defects.

Furthermore, there’s some support for the link between the use of marijuana during pregnancy and later neurodevelopmental problems in the child. These could include impulsivity and hyperactivity as well as problems with abstract and visual reasoning.

No safe level of marijuana has been determined for those who are planning on becoming pregnant or are pregnant. The effects of CBD on pregnancy are also largely unknown. Thus, it’s best for people not to smoke or otherwise consume marijuana at conception or during pregnancy. If you need marijuana for a medical condition, discuss this with your OB-GYN.

Infections While Pregnant

Certain infections during pregnancy can lead to birth defects. Many infections can be prevented by staying away from people who are sick, frequent handwashing, and thoroughly cooking meat. Furthermore, certain vaccines protect a person from infections that can lead to birth defects. The seasonal flu vaccine is always recommended for pregnant people.


While the overall risk is low, pregnant people are at increased risk for severe illness from COVID-19 when compared to non-pregnant people. They are more likely to require hospitalization, breathing support, care in an intensive care unit (ICU), and to die from complications. In addition, COVID-19 may place people at increased risk of poor pregnancy outcomes.

Factors that can increase a pregnant person's risk for severe illness include:

  • Preexisting health conditions
  • Being older than 25
  • Health and social inequities

According to the CDC, if you are pregnant, you can receive the COVID-19 vaccine. Vaccine monitoring has not found any safety concerns for pregnant people or their babies.

Some newborns test positive for COVID-19 shortly after birth. It is not known if they contract it in utero, during birth, or after they are born. Fortunately, most newborns with COVID-19 have mild or no symptoms. However, there have been some severe cases.

Parents who test positive for COVID-19 at the time of giving birth should take precautions. Wear a mask when you are within six feet of your baby and wash your hands frequently, especially before handling your baby.

Current evidence suggests that breast milk is not likely to transmit the virus to babies. If you have COVID-19, be sure to wash your hands thoroughly before handling your baby and wear a mask while you breastfeed.

Zika Virus

Zika virus causes birth defects in babies born to infected parents. These birth defects include microcephaly (small head) and brain abnormalities. However, the transmission of the Zika virus in the continental United States is still relatively rare, and infection with other teratogenic viruses is much more common.


Cytomegalovirus (CMV) is the most common cause of infection in newborns. A majority of people have CMV antibodies. Most commonly, primary infection with CMV (infection for the first time) leads to a risk of CMV in the newborn (i.e., congenital CMV). Nevertheless, reactivation of CMV or infection of the parent with a different strain can also lead to congenital CMV.

Most people who have been infected with CMV show no signs of infection and experience no symptoms. A person with a healthy immune system can keep infection with CMV in check. However, CMV can cause serious infection in those with weaker immune systems. Moreover, CMV can endanger the fetus and can lead to birth defects.

Most babies born with CMV infection are healthy. About one in five babies born with CMV infection are sick at birth or go on to develop long-term health problems. Some babies show signs of CMV infection at birth. A minority of babies appear healthy at birth but go on to later develop signs of infection, such as hearing loss. Other repercussions of CMV infection in newborns include:

  • Chorioretinitis (inflammation of the choroid and retina) and other eye problems
  • Dental problems
  • Enlargement of the liver and spleen
  • Hemolytic anemia (an autoimmune blood disorder)
  • Hepatitis
  • Intellectual disability
  • Intracranial calcifications
  • Jaundice
  • Liver, lung, and spleen problems
  • Microcephaly
  • Petechiae (i.e., small red or purple spots on the skin caused by broken capillaries)
  • Psychomotor issues
  • Seizures
  • Small size at birth

It is difficult to predict which babies will develop serious CMV infections, and there is no treatment for CMV infection during pregnancy that will prevent disease in the newborn. CMV can be transmitted from one person to another by close contact, such sexual intercourse or exposure to saliva.

Prescription Medications in Pregnancy

Many medications have adverse effects that can affect pregnancy. However, only about 30 drugs are known teratogens, which can cause birth defects. Potential teratogenic effects include the following:

  • Behavioral toxicities (i.e., adverse effects of drugs that impair the performance of everyday activities)
  • Death of the fetus
  • Intrauterine growth restriction
  • Malformations
  • Neonatal toxicities

Until the middle of the twentieth century, physicians believed that the fetus lived in a protected environment separate from the parent. This belief that fetuses were protected from prescription drugs and other potentially toxic substances came crashing down after the effects of thalidomide resulted in widespread tragedy in the 1960s.

Thalidomide was used to treat morning sickness but resulted in profound limb malformations, facial malformations, and other problems in newborns. Ever since the thalidomide tragedy, physicians have gingerly approached the prescription of drugs during pregnancy for fear of teratogenic effects. Fortunately, many teratogenic agents are not prescribed during pregnancy.

Here are some known drugs that are teratogens:

  • ACE inhibitors
  • Carbamazepine
  • Cyclophosphamide
  • Diethylstilboestrol
  • Isotretinoin
  • Lithium
  • Phenytoin
  • Tetracycline
  • Warfarin

Lack of Folic Acid

Folate, or folic acid, is a type of B vitamin. During pregnancy, the need for folate increases between five and ten times because this vitamin is transferred to the fetus. Folate deficiency can be hard to detect during pregnancy, and even a well-nourished person may experience it. Of note, green, leafy vegetables are high in folate.

Because half of all pregnancies in the United States are unplanned and folate deficiency can affect a fetus early on—before a person even knows that they're pregnant—the CDC recommends that anyone who could conceive (between the ages of 15 and 45) should take 400 micrograms of folate daily. Most prenatal vitamins contain more than this (600 to 1000 micrograms).

The following factors increase the need for folate in the parent:

  • Anticonvulsant medications
  • Breastfeeding
  • Coexisting anemia
  • Infection
  • Poor diet

Folate deficiency can lead to serious birth defects including spina bifida and anencephaly. Both of these conditions are neural tube defects. With spina bifida, the bones of the spine don’t properly form around the spinal cord. With anencephaly, parts of the head and brain don’t properly form.

Research shows that folic acid supplementation at the time of conception continued through the first 12 weeks of pregnancy can decrease the risk of neural tube defects by about 70%.

Chronic Health Conditions

Uncontrolled diabetes during pregnancy as well as obesity before and during pregnancy can both increase the risk of birth defects as well as other serious health conditions. If diabetes is poorly controlled during pregnancy, higher blood sugars can affect both the fetus and the parent.

Babies born to parents with diabetes are typically much larger and have larger organs, which makes the birth process much more difficult. These babies also experience low blood sugars after birth. Furthermore, babies born to parents with diabetes are at increased risk of being stillborn, and fetuses are at increased risk of miscarriage. Specific conditions experienced by babies born to parents with diabetes may include:

  • Blue and mottled skin, rapid heart rate and rapid breathing (signs of lung and heart failure)
  • Congenital heart defects
  • Jaundice
  • Lethargy
  • Poor feeding
  • Puffiness
  • Tremors

People with diabetes should try to achieve a healthy weight before conceiving. During pregnancy, people with diabetes should work to limit weight gain as well as exercise, monitor blood sugar, and take medications as prescribed by a physician. Similarly, people with obesity should try to lose weight before conceiving.

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27 Sources
Verywell Family uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. U.S. National Library of Medicine. Birth defects. Updated March 9, 2021. 

  2. Centers for Disease Control and Prevention. Data & statistics on birth defects. Updated January 23, 2020.

  3. Chambers C, Alwan S. Identifying human teratogens: An update. J Pediatr Genet. 2015;04(02):039-041. doi:10.1055/s-0035-1556745

  4. Centers for Disease Control and Prevention. Alcohol use in pregnancy. Updated March 27, 2018.

  5. Centers for Disease Control and Prevention. Unintended pregnancy. Updated September 12, 2019.

  6. Centers for Disease Control and Prevention. Basics about FASDs. Updated May 21, 2021.

  7. Vorgias D, Bernstein B. Fetal alcohol syndrome. National Center for Biotechnology Information, U.S. National Library of Medicine. Updated August 23, 2020. 

  8. Burd L, Blair J, Dropps K. Prenatal alcohol exposure, blood alcohol concentrations and alcohol elimination rates for the mother, fetus and newborn. J Perinatol. 2012;32(9):652-659. doi:10.1038/jp.2012.57

  9. National Center for Chronic Disease Prevention and Health Promotion (US) Office on Smoking and Health. The health consequences of smoking—50 years of progress: A report of the surgeon general. Atlanta (GA): Centers for Disease Control and Prevention; 2014. 9, Reproductive Outcomes.

  10. Mund M, Louwen F, Klingelhoefer D, Gerber A. Smoking and pregnancy--a review on the first major environmental risk factor of the unborn. Int J Environ Res Public Health. 2013;10(12):6485-99. doi:10.3390/ijerph10126485

  11. Blood-Siegfried J, Rende EK. The long-term effects of prenatal nicotine exposure on neurologic development. J Midwifery Womens Health. 2010;55(2):143-52. doi:10.1016/j.jmwh.2009.05.006

  12. El-Ardat MA, Izetbegovic S, El-Ardat KA. Effect of cigarette smoking in pregnancy on infants anthropometric characteristics. Mater Sociomed. 2014;26(3):186-7. doi:10.5455/msm.2014.26.186-187

  13. Centers for Disease Control and Prevention. What you need to know about marijuana use and pregnancy. Updated March 16, 2018.

  14. Grant KS, Petroff R, Isoherranen N, Stella N, Burbacher TM. Cannabis use during pregnancy: Pharmacokinetics and effects on child development. Pharmacol Ther. 2018;182:133-151. doi:10.1016/j.pharmthera.2017.08.014

  15. American Academy of Pediatrics. Simple steps to prevent infections during pregnancy. Updated November 19, 2019.

  16. Centers for Disease Control and Prevention. Pregnant and recently pregnant people. Updated June 10, 2021.

  17. Centers for Disease Control and Prevention. COVID-19 vaccines while pregnant or breastfeeding. Updated June 16, 2021.

  18. Centers for Disease Control and Prevention. Breastfeeding and caring for newborns. Updated May 13, 2021.

  19. Leeper C, Lutzkanin A. Infections during pregnancy. Prim Care. 2018;45(3):567-586. doi:10.1016/j.pop.2018.05.013

  20. Pass RF, Anderson B. Mother-to-child transmission of cytomegalovirus and prevention of congenital infection. J Pediatric Infect Dis Soc. 2014;3 Suppl 1:S2-6. doi:10.1093/jpids/piu069

  21. Centers for Disease Control and Prevention. Congenital CMV and hearing loss. Updated May 31, 2019.

  22. March of Dimes. Prescription medicine during pregnancy. Updated October 2017.

  23. Centers for Disease Control and Prevention. Recommendations: Women and folic acid. Updated August 13, 2019.

  24. Gabbay-Benziv R, Reece EA, Wang F, Yang P. Birth defects in pregestational diabetes: Defect range, glycemic threshold and pathogenesis. World J Diabetes. 2015;6(3):481-8. doi:10.4239/wjd.v6.i3.481

  25. Negrato CA, Mattar R, Gomes MB. Adverse pregnancy outcomes in women with diabetes. Diabetol Metab Syndr. 2012;4(1):41. doi:10.1186/1758-5996-4-41

  26. National Institute of Diabetes and Digestive and Kidney Diseases. Pregnancy if you have diabetes. Updated January 2017.

  27. American College of Obstetricians and Gynecologists. Obesity and pregnancy. Updated May 2019.

Additional Reading
  • Barbieri RL, Repke JT. Medical disorders during pregnancy. In: Kasper D, Fauci A, Hauser S, Longo D, Jameson J, Loscalzo J. eds. Harrison's Principles of Internal Medicine, 19e. McGraw-Hill; 2014.

  • Hoffbrand A. Megaloblastic anemias. In: Kasper D, Fauci A, Hauser S, Longo D, Jameson J, Loscalzo J. eds. Harrison's Principles of Internal Medicine, 19e . McGraw-Hill; 2014.

  • Masters SB, Trevor AJ. The alcohols. In: Katzung BG, Trevor AJ. eds. Basic & Clinical Pharmacology, 13e. McGraw-Hill; 2015.

  • Powrie RO, Rosene-Montella K. Medication management. In: McKean SC, Ross JJ, Dressler DD, Scheurer DB. eds. Principles and Practice of Hospital Medicine, 2e. McGraw-Hill; 2016.