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This pages serves to highlight the latest objective research, news, and professional guidance and recommendations regarding pregnancy-related health.

*NEW: New page published! Read evidence-based information on the prevention and management of varicose veins in pregnancy.

*NEW: "Medical Community Tweets" section added (July 20, 2021)

UPDATED: "Heat Exposure" research added (section added June 29, 2021)

As of July 2021, COVID-19 and heat stress are the current major health-related issues that could adversely affect pregnant women.

This page will highlight COVID-19 infection and vaccine-safety data as it is published/released, as well as evidence-based information on how women can avoid heat-related effects during pregnancy.

Additional highlights and research updates on other topics are also listed below. Women should talk to their health care provider (HCP) if they have any questions.

Note: Unless ongoing, highlights are kept on this page for approximately 30 days before being removed or added to a permanent Topic page.

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Latest Page Updates

NEW page published (July 22, 2021): Varicose Veins

Pages updated within the past week (July 25, 2021):


Latest Research/Recommendations

July 22, 2021: Laboratory study indicated it is possible for COVID-19 to be replicated in the early trophoblast (it is possible that COVID-19 could infect a very early embryo, potentially causing miscarriage or implantation failure). The study only determined the pathway appears to exist, but no human data are published.

July 20, 2021: Study suggests that there is insufficient knowledge about dental imaging safety during pregnancy in the general population. This misconception may have a direct impact on the attitude toward pregnant women seeking dental care. Learn more about radiation risks in pregnancy (to include the safety of dental x-rays, here).

Photo by Mediamodifier on Unsplash

July 20, 2021: A total of 515 women were included in a recent study and headache disorders were reported in 43.5% of participants (224/515). The study concluded that migraine with aura and tension type headache may expose women to an increased risk of delivering small for gestational age infants. Further, admission to the neonatal intensive care unit was significantly higher in all the headache groups. The authors indicated pregnant women with a headache disorder may need to be watched more closely to avoid complications.

July 12, 2021: BNT162b2 (Pfizer) mRNA vaccination during pregnancy compared with no vaccination was associated with a significantly lower risk of COVID-19 infection (1.6% vs. 2.7%).

July 7, 2021: Cleft palate is amongst the most common birth defect across the world; new study evaluated whether its incidence was changing over time. The authors concluded, based on the rate of corrective surgeries, that cleft palate has been significantly decreasing over the last two decades and may represent improvements in early diagnosis in pregnancy, changing genetic or racial demographics, and/or environmental factors such as decreased maternal smoking in the US population.

July 3, 2021: In one medical center, of 10,731 prenatal telehealth appointments (compared to controls), this method of care did not compromise pregnancy outcomes; the authors suggested that pregnant individuals should have access to virtual appointments even after the pandemic.

July 1, 2021:  Study presented July 1 at the European Society of Human Reproduction and Embryology Conference assessed non-prescription painkillers and perinatal health risks.  A total of 151,141 singleton pregnancies were analyzed using medical notes for consumption of five painkillers – paracetamol (acetaminophen), aspirin, and non-steroidal anti-inflammatory drugs (NSAIDs), diclofenac, naproxen and ibuprofen – either as single compounds or in combinations.

The findings show an association between increased health risks when pregnancies were exposed to at least one of the five analgesics. However, and of note, details on the timing, dosage, product type (single-ingredient vs combination) and administration were not available.

Learn more about this study here, and read our acetaminophen page to better understand why these medications are so difficult to study in pregnancy.

June 28, 2021: Study aimed to reveal the relationship between short and long interpregnancy intervals (IPI) (time between each pregnancy) and adverse birth outcomes (among 13,231 women). Compared with the reference group, infants with a short IPI (less than 6 months) had higher risks of small-for-gestational age and birth defects and those with a long IPI (longer than 12 months) had higher risks of low birth weight and preterm birth.


Medical Community Tweets (July 20)

Tweets from health care professionals & obstetric organizations have valuable, timely information. We are now embedding these tweets so you (or your patients or clients) have even more access to reliable information. More:

COVID-19 vaccines and fertility:

Incredible photograph of a fetus in the womb during fetal surgery:

Analysis on the option of expectant management (watchful waiting) of ectopic pregnancy: [Note: This option is not best for all cases. It is still critically important for pregnant women to call their health care provider if they are experiencing symptoms of ectopic pregnancy]:

Click the thread below to learn more information on current data regarding possible long-term effects on babies born after maternal COVID-19 vaccination:

According to the study highlighted below, "COVID-19 during pregnancy is strongly associated with preeclampsia, especially among...women [pregnant for the first time]." However, more research is necessary as certain elements of COVID-19 could be mimicking preeclampsia. Read the full study:

Learn more about midwifery below:

Largest cohort of pregnant women tested for COVID-19 worldwide; severe adverse outcomes (maternal death, admission to ICU and/or advanced oxygen support) were observed in 9.9% of cases. Pulmonary (respiratory) comorbidities, hypertensive disorders and diabetes were significantly associated with an increased risk of severe maternal outcomes. Obstetrical and newborn outcomes are influenced by the severity of maternal disease. Read the full report below:

Importance of folic acid supplementation for pregnant women with epilepsy:


Heat Exposure

Hyperthermia (opposite of hypothermia, which occurs from “cold” exposure) is emerging as a risk factor for potential negative outcomes regarding fetal development. 

Current evidence indicates that prolonged exposure to heat can raise the body’s core temperature and potentially induce harmful effects on the fetus, especially in the first trimester.  However, “prolonged” exposure is not defined, and the minimum core body temperature at which damage may begin is not known for certain (currently assessed to begin at a body temperature of 102° F/38.9° C).

Any source of heat that can raise core body temperature during pregnancy for a prolonged period may lead to adverse pregnancy outcomes, depending on length and frequency of exposure.

Pregnant women are advised to:

  • Avoid prolonged exposure to hot weather

  • Remain in air conditioned rooms when possible

  • Stay hydrated

  • Protect the skin with sunscreen, light clothing, and hats

  • Avoid exercising in hot weather and hot environments (e.g. hot yoga); see our Exercise page for more information

  • Replace sweat lost with additional fluids, to include fluids with electrolytes if necessary

  • Keep shower and bath length (when using hot water) to 10 minutes or less (to be cautious)

  • Learn to recognize the signs and symptoms of heat stroke and exhaustion in order to ask for help when necessary

Learn much more detail about Heat Exposure here.

Recent Heat-Related Research:

A study published in June 2021 provides evidence that individuals in their second and third trimester of pregnancy are not at greater risk for hyperthermia during moderate exercise in the heat (45 minutes, 32 °C/89.6 °F). Although pregnant women felt hotter, their body temperatures and sweat output were not different than the control group; core temperature of all pregnant participants never exceeded 38 °C/100.4 °F.

Of note, however, it is possible that higher intensity exercise, or shorter bouts of high intensity exercises in a climate above 32 °C/89.6 °F (or with higher humidity), could raise body temperature higher than observed in this study. Further, this study size was small and body temperature can vary widely among different individuals.

A study published in July 2021 reviewed all emergency department (ED) visits and hospital admissions due to pregnancy complications from 2005 to 2013 in New York State. Daily mean temperature > 90th percentile of the monthly mean temperature in each county was defined as an Extreme Heat Exposure (EHE).

The study determined EHE was significantly associated with increased ED visits for pregnancy complications in summer. There was also a significant and stronger association in transitional months (May and September). The authors noted that "earlier warnings regarding extreme heat are recommended to decrease pregnancy complications."

A study published in April 2020 suggested that acute exposure to extreme heat during the last week of gestation may adversely trigger an earlier delivery. Approximately 7% of the cohort had a preterm birth. For all definitions of extreme heat, the risk of preterm birth was consistently higher among mothers who experienced an extreme heat episode during their last week of gestation.


COVID-19 and Vaccines

Background: In March 2020, the World Health Organization officially declared a worldwide pandemic of a new respiratory infection called coronavirus 2019 (COVID-19), more formally “severe acute respiratory syndrome coronavirus 2” or SARS-CoV-2.

As of July 25, 2021, the U.S. Centers for Disease Control and Prevention (CDC) estimates the virus has caused approximately 34,380,019 illnesses and 608,403 deaths.

General COVID-19 information and pregnancy health: According to currently available case series and cohorts as of June 2021, data indicates pregnant women are not more susceptible to the disease than non-pregnant women, and fetal and symptomatic neonatal infection appear to be rare events.

Weekly COVID-19 Pregnancy Data from CDC:

  • Total Cases: 101,710

  • Hospitalized: 17,380 (data only available for 81,138)

  • Total Deaths: 114

*As of July 23, 2021

These numbers likely do not include all pregnant women with COVID-19 in the United States and must be interpreted with caution.

However, according to two large CDC reports (September and November 2020), pregnant women who contract COVID-19 appear to be at higher risk of complications from the disease than non-pregnant women of reproductive age. These complications include Intensive Care Unit admission, the need for mechanical ventilation, and the need for extracorporeal membrane oxygenation (ECMO).

There are currently three COVID-19 vaccines in the United States that have been given Emergency Use Authorization by the FDA: Pfizer-BioNTech, Moderna, and Johnson & Johnson/Janssen.

Photo by Mufid Majnun on Unsplash

The FDA does not have a specific recommendation regarding whether one vaccine is more preferable over another, to include during pregnancy and lactation. It is recommended by numerous expert panels and obstetric organizations that women choose for themselves whether they would like to be vaccinated, after consultation with their HCP.

In the U.K., the Pfizer-BioNTech, Moderna, and Vaxzevria (formerly Oxford-AstraZeneca) vaccines are currently authorized by its vaccine regulator, the Medicines and Healthcare products Regulatory Agency.

Read more on COVID-19, pregnancy, and more detailed vaccine information and guidance from the American College of Obstetricians and Gynecologists (ACOG), the Society for Maternal-Fetal Medicine, and the Royal College of Obstetricians and Gynaecologists here.


Women should talk to their HCP if they any questions related to any of the updates above. Not all pregnant women who contract COVID-19 will have serious illness. However, there is currently no way to determine which women may experience a more severe course of the infection.

It is recommended that pregnant women:

  • Seek care immediately or dial 911 if experiencing a medical emergency. Emergency symptoms can include trouble breathing, persistent pain or pressure in the chest, new confusion, inability to wake or stay awake, or bluish lips or face. This is not an inclusive list, and women should always call their HCP or visit an emergency room when necessary.

  • Report any and all symptoms of a respiratory infection to their HCP, to include cough, fevershortness of breath, and diarrhea

  • Avoid unnecessary traveling, use of public transportation, and contact with sick people

  • Wear a mask (to protect others) in public settings

  • Follow personal and social distancing rules

  • Regularly wash hands for at least 20 seconds (if soap and water are not readily available, use a hand sanitizer that contains at least 60% alcohol)

  • Avoid touching their eyes, nose, and mouth with unwashed hands.

  • Do not skip prenatal care appointments or other health appointments that may be necessary

  • Make sure to have at least a 30-day supply of prescription medications

  • Learn about stress and coping

  • Get adequate sleep and physical exercise

  • Quit smoking (risk factor for infection)

  • Go outside in open areas for walks, fresh air, and a change of scenery

Any pregnant woman who has traveled in a state or country with a high rate of COVID-19 infection or who has had close contact with an individual with confirmed infection should be tested and quarantined.

Pregnant women are also advised to see their HCP immediately or call 911 if they experience:

  • Difficulty breathing or shortness of breath

  • Persistent pain or pressure in the chest or abdomen

  • Persistent dizziness, confusion, inability to arouse

  • Seizures

  • Not urinating

  • Severe muscle pain and/or weakness

  • Fever or cough that improves but then returns or worsens (may indicate pneumonia)

  • High fever that is not responding to acetaminophen or other anti-fever medication (acetaminophen is not an NSAID)

Women should refer to the CDC and ACOG COVID-19 web pages below for additional information.


Total cases in the United States/COVID tracker (U.S. Centers for Disease Control and Prevention)

COVID-19 Home Page (U.S. Centers for Disease Control and Prevention)

ACOG Statement on COVID-19 and Pregnancy (American College of Obstetricians and Gynecologists; June 2020)

Coronavirus (COVID-19), Pregnancy, and Breastfeeding: A Message for Patients (American College of Obstetricians and Gynecologists)

The Management of Respiratory Infections During Pregnancy (Immunology and Allergy Clinics of North America; 2006)


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