Welcome to The Visible Embryo
The Visible Embryo Birth Spiral Navigation
Fetal Timeline--- -Maternal Timeline-----News-----Prescription Drugs in Pregnancy---- Pregnancy Calculator----Female Reproductive System

WHO International Clinical Trials Registry Platform

The World Health Organization (WHO) has a Web site to help researchers, doctors and patients obtain information on clinical trials.

Now you can search all such registers to identify clinical trial research around the world!




Pregnancy Timeline

Prescription Drug Effects on Pregnancy

Pregnancy Calculator

Female Reproductive System


Disclaimer: The Visible Embryo web site is provided for your general information only. The information contained on this site should not be treated as a substitute for medical, legal or other professional advice. Neither is The Visible Embryo responsible or liable for the contents of any websites of third parties which are listed on this site.

Content protected under a Creative Commons License.
No dirivative works may be made or used for commercial purposes.


Pregnancy Timeline by SemestersDevelopmental TimelineFertilizationFirst TrimesterSecond TrimesterThird TrimesterFirst Thin Layer of Skin AppearsEnd of Embryonic PeriodEnd of Embryonic PeriodFemale Reproductive SystemBeginning Cerebral HemispheresA Four Chambered HeartFirst Detectable Brain WavesThe Appearance of SomitesBasic Brain Structure in PlaceHeartbeat can be detectedHeartbeat can be detectedFinger and toe prints appearFinger and toe prints appearFetal sexual organs visibleBrown fat surrounds lymphatic systemBone marrow starts making blood cellsBone marrow starts making blood cellsInner Ear Bones HardenSensory brain waves begin to activateSensory brain waves begin to activateFetal liver is producing blood cellsBrain convolutions beginBrain convolutions beginImmune system beginningWhite fat begins to be madeHead may position into pelvisWhite fat begins to be madePeriod of rapid brain growthFull TermHead may position into pelvisImmune system beginningLungs begin to produce surfactant
CLICK ON weeks 0 - 40 and follow along every 2 weeks of fetal development

Developmental Biology - Pregnancy Scans

Worry Over Increased Medical Scans in Pregnancy

First large study of CT scans over two decades documents rise in radiation exposure...

Use of medical imaging during pregnancy has increased significantly in the United States, a new study has found. With nearly a four-fold rise over the last two decades, the number of women undergoing computed tomography (CT) scans exposes mothers and fetuses to increased amounts of radiation even as pregnant women are warned to minimize radiation exposure.

In the first large, multi-center study to assess the amount of advanced imaging occurring during pregnancy, the study includes researchers from University of California San Francisco (UCSF), University of California Davis and Kaiser Permanente. The results were published July 24, 2019, in JAMA Network Open.
Over the 21-year study period, rates of CT increased nearly four-fold in the United States, and doubled in Ontario, Canada.

"Most pregnant women get routine ultrasound to monitor fetal growth, which delivers no ionizing radiation," said co-lead author Diana L. Miglioretti PhD, biostatistics professor at the UC Davis Department of Public Health Sciences and senior investigator with Kaiser Permanente Washington Health Research. "But occasionally, doctors may want to use advanced imaging to detect or rule out a serious medical condition of the expectant mother, most often pulmonary embolism, brain trauma or aneurysm, or appendicitis."
CT imaging involves a large dose of ionizing radiation - many times more than a chest X-ray. Ionizing radiation carries potential health risks to the developing fetus, including congenital abnormalities, developmental delays, or cancer.

"Imaging can be helpful, but it can be overused," said senior author Rebecca Smith-Bindman, MD, a UCSF professor of radiology, epidemiology and biostatistics; obstetrics, gynecology and reproductive medicine. "Always, but especially if you're pregnant, you should ask whether it is really medically necessary to have any imaging test that involves ionizing radiation."

The researchers say alternative methods that do not use radiation should be considered whenever possible to avoid unnecessary exposure of women and fetuses to imaging radiation.
"There's a tradeoff. CT scans provide the clearest images, they can be done quickly, and are less expensive and more widely available. However, CT scans have the most ionizing radiation and they are commonly done in places of the body where the fetus is exposed to the radiation."

Rebecca Smith-Bindman MD, University of California San Francisco, Professor, Radiology, Epidemiology, Biostatistics; Obstetrics, Gynecology and Reproductive Medicine.

The authors said that professional organizations have not consistently recommended minimizing medical imaging during pregnancy. Their research opens a new avenue of inquiry into the potential risks involved.

"This study has given us a chance to look more closely at the use of advanced imaging in pregnancy," said Marilyn L. Kwan, co-lead author and senior research scientist in the Kaiser Permanente Northern California Division of Research. "It's important to quantify exposure to ionizing radiation because it can cause cancer and birth defects, and should be kept to a minimum, especially during pregnancy."

The study tracked the combined use of advanced medical imaging during pregnancy and researchers analyzed more than 3.5 million pregnancies at six U.S. health systems and the provincial health system of Ontario, Canada, between January 1, 1996, and December 31, 2016. They reviewed the use of advanced imaging, including CT, magnetic resonance imaging (MRI), conventional radiography, angiography and nuclear medicine.

During the 21-year study, 5.3 percent of pregnant women at U.S. sites and 3.6 percent in Ontario underwent imaging with ionizing radiation, the authors said.
Rates of CT scanning during pregnancy in the U.S. started leveling off in 2007 and have been trending downward since 2010.

Meanwhile, overall rates continued to climb in Ontario, but in 2016, were 33 percent lower than in the U.S. The study also found Ontario used MRI, which doesn't use radiation, more often than CT, which does.

Importance The use of medical imaging has sharply increased over the last 2 decades. Imaging rates during pregnancy have not been quantified in a large, multisite study setting.

To evaluate patterns of medical imaging during pregnancy.

Design, Setting, and Participants
A retrospective cohort study was performed at 6 US integrated health care systems and in Ontario, Canada. Participants included pregnant women who gave birth to a live neonate of at least 24 weeks’ gestation between January 1, 1996, and December 31, 2016, and who were enrolled in the health care system for the entire pregnancy.

Computed tomography (CT), magnetic resonance imaging, conventional radiography, angiography and fluoroscopy, and nuclear medicine.

Main Outcomes and Measures
Imaging rates per pregnancy stratified by country and year of child’s birth.

A total of 3?497?603 pregnancies in 2?211?789 women were included. Overall, 26% of pregnancies were from US sites. Most (92%) were in women aged 20 to 39 years, and 85% resulted in full-term births. Computed tomography imaging rates in the United States increased from 2.0 examinations/1000 pregnancies in 1996 to 11.4/1000 pregnancies in 2007, remained stable through 2010, and decreased to 9.3/1000 pregnancies by 2016, for an overall increase of 3.7-fold. Computed tomography rates in Ontario, Canada, increased more gradually by 2.0-fold, from 2.0/1000 pregnancies in 1996 to 6.2/1000 pregnancies in 2016, which was 33% lower than in the United States. Overall, 5.3% of pregnant women in US sites and 3.6% in Ontario underwent imaging with ionizing radiation, and 0.8% of women at US sites and 0.4% in Ontario underwent CT. Magnetic resonance imaging rates increased steadily from 1.0/1000 pregnancies in 1996 to 11.9/1000 pregnancies in 2016 in the United States and from 0.5/1000 pregnancies in 1996 to 9.8/1000 pregnancies in 2016 in Ontario, surpassing CT rates in 2013 in the United States and in 2007 in Ontario. In the United States, radiography rates doubled from 34.5/1000 pregnancies in 1996 to 72.6/1000 pregnancies in 1999 and then decreased to 47.6/1000 pregnancies in 2016; rates in Ontario slowly increased from 36.2/1000 pregnancies in 1996 to 44.7/1000 pregnancies in 2016. Angiography and fluoroscopy and nuclear medicine use rates were low (5.2/1000 pregnancies), but in most years, higher in Ontario than the United States. Imaging rates were highest for women who were younger than 20 years or aged 40 years or older, gave birth preterm, or were black, Native American, or Hispanic (US data only). Considering advanced imaging only, chest imaging of pregnant women was more likely to use CT in the United States and nuclear medicine imaging in Ontario.

Conclusions and Relevance
The use of CT during pregnancy substantially increased in the United States and Ontario over the past 2 decades. Imaging rates during pregnancy should be monitored to avoid unnecessary exposure of women and fetuses to ionizing radiation.

Marilyn L. Kwan PhD, Diana L. Miglioretti PhD, Emily C. Marlow MPH, E. J. Aiello Bowles MPH, Sheila Weinmann PhD, Stephanie Y. Cheng MSc, Kamala A. Deosaransingh MPH, Prachi Chavan MPH, Lisa M. Moy MPH, Wesley E. Bolc, PhD, James R. Duncan MD PhD, Robert T. Greenlee PhD, Lawrence H. Kushi ScD, Jason D. Pole PhD, Alanna K. Rahm PhD, Natasha K. Stout PhD, R. Smith-Bindman MD.

Conflict of Interest Disclosures: Dr Duncan reported personal fees from Bayer Healthcare outside the submitted work. Dr Greenlee reported grants from the University of California, San Francisco during the conduct of the study. No other disclosures were reported.

Funding/Support: This study was supported by the National Cancer Institute at the National Institutes of Health (grants R01CA185687, R50CA211115, and U24CA171524). The Ontario, Canada, portion of the study was also supported by ICES, which is funded by an annual grant from the Ontario Ministry of Health and Long-Term Care.

Role of the Funder/Sponsor: The National Cancer Institute, National Institutes of Health, and ICES had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.

Return to top of page.

Aug 14 2019   Fetal Timeline   Maternal Timeline   News  

Computed Tomography (CT) scan of twins in utero. CREDIT Public Domain

Phospholid by Wikipedia