How to Keep Your Unborn Baby Healthy

Environmental factors and genetics can be responsible for birth defects

Active pregnant woman hiking

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 birth defects are readily noticeable, such as cleft lip or palate. Other birth defects 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), the fetus is most susceptible to the effects of teratogens and severe birth defects can result. More specifically, major organs develop during this period. It should be noted that 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, however. Ultimately, environmental and genetic factors conflate to result in these problems. Maintaining a healthy lifestyle and regular meetings with your OB-GYN before and during pregnancy can help you have a healthy baby. Nevertheless, there are steps that you can take to limit your risk of having a baby with birth defects.

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What Do You Have to Give Up While Pregnant?

Alcohol During Pregnancy

Consumption of 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 woman drinks alcohol, so does her baby. Furthermore, half of all pregnancies in the United States are unplanned. It can take between 4 and 6 weeks before a woman knows if she’s pregnant. During this period, alcohol could interfere with fetal development. Consumption of alcohol during pregnancy can lead to fetal alcohol syndrome (FAS).

Minimal limits of alcohol and FAS have not been determined. Abnormalities observed with FAS include the following:

  • Congenital heart defects
  • Flattened face secondary to the underdeveloped midface
  • Intellectual disability
  • Intrauterine growth restriction (i.e., poor growth of the baby while in the womb)
  • Joint anomalies
  • Microcephaly (i.e., 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 circulation. In the unborn baby’s blood, alcohol reaches concentrations comparable with those observed in the mother’s circulation.

However, fetuses essentially lack the enzyme alcohol dehydrogenase, which is produced by the liver and needed to break down alcohol. Instead, babies rely on placental and maternal enzymes to clear alcohol. These enzymes aren’t nearly as effective as alcohol dehydrogenase at metabolizing alcohol; thus, 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 mother who is still smoking, it’s never too late to quit. Moreover, pregnant women should stay away from second-hand smoke.

Here are some adverse effects that a baby born to a mother who smokes during pregnancy may experience:

  • Cleft lip
  • Cleft palate
  • Increased excitability (hyperexcitability)
  • Increased muscle tone (hypertonicity)
  • Intrauterine growth restriction
  • Irritability
  • Preterm labor
  • SIDS
  • Tremors

Nicotine is 15% more concentrated in the blood of the fetus than in that of the mother. The more heavily that a mother smokes, the increased 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 "Street" Drugs

Marijuana is the most commonly used street 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 woman 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, such as impulsivity and hyperactivity as well as problems with abstract and visual reasoning.

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

Preventing Infections While Pregnant

Certain infections during pregnancy can lead to birth defects. Infections can be prevented by taking certain steps, including staying away from people with infections, frequent handwashing, and thoroughly cooking meat.

Furthermore, certain vaccines protect a woman from infections that can lead to birth defects. The seasonal flu vaccine is always recommended for pregnant women.


There is limited information about COVID-19 (the illness caused by the novel coronavirus) in pregnancy. Some small studies have shown no adverse outcomes for babies when their mothers had COVID-19 in their third trimester.

Effects of COVID-19 in earlier trimesters and long term are largely unknown at this time. Like everyone else, especially people at higher risk, pregnant women should wash their hands frequently and avoid people who are sick.

Zika Virus

Zika virus causes birth defects in babies born to infected mothers. 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 women 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 mother 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 of 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.

Here are some potential repercussions of CMV infection in the newborn:

  • Chorioretinitis (i.e., inflammation of the choroid and retina) and other eye problems
  • Dental problems
  • Enlargement of the liver and spleen
  • Hearing problems
  • 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 means of saliva, sexual intercourse, and so forth.

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 mother. 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 so forth 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

The Importance of Folate Supplements

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 woman 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 mother even knows that she’s pregnant—the CDC recommends that all women of reproductive age (between 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 mother:

  • 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%.

Maintaining a Healthy Lifestyle

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 mother.

Babies born to mothers 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 mothers with diabetes are at increased risk of being stillborn, and fetuses are at increased risk of miscarriage.

Here are some specific conditions experienced by babies born to mothers with diabetes:

  • 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

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

Similarly, obese women should try to lose weight before conceiving through diet, exercise, and other lifestyle modifications.

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

  • 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 New York, NY: McGraw-Hill; 2014.