Welcome to The Visible Embryo



Home-- -History-- -Bibliography- -Pregnancy Timeline- --Prescription Drugs in Pregnancy- -- Pregnancy Calculator- --Female Reproductive System- -Contact

Welcome to The Visible Embryo, a comprehensive educational resource on human development from conception to birth.

The Visible Embryo provides visual references for changes in fetal development throughout pregnancy and can be navigated via fetal development or maternal changes.

The National Institutes of Child Health and Human Development awarded Phase I and Phase II Small Business Innovative Research Grants to develop The Visible Embryo. Initally designed to evaluate the internet as a teaching tool for first year medical students, The Visible Embryo is linked to over 600 educational institutions and is viewed by more than one million visitors each month.

Today, The Visible Embryo is linked to over 600 educational institutions and is viewed by more than 1 million visitors each month. The field of early embryology has grown to include the identification of the stem cell as not only critical to organogenesis in the embryo, but equally critical to organ function and repair in the adult human. The identification and understanding of genetic malfunction, inflammatory responses, and the progression in chronic disease, begins with a grounding in primary cellular and systemic functions manifested in the study of the early embryo.

WHO International Clinical Trials Registry Platform

The World Health Organization (WHO) has created a new Web site to help researchers, doctors and
patients obtain reliable information on high-quality clinical trials. Now you can go to one website and search all registers to identify clinical trial research underway around the world!




Pregnancy Timeline

Prescription Drug Effects on Pregnancy

Pregnancy Calculator

Female Reproductive System

Contact The Visible Embryo

News Alerts Archive

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 SemestersFetal liver is producing blood cellsHead may position into pelvisBrain convolutions beginFull TermWhite fat begins to be madeWhite fat begins to be madeHead may position into pelvisImmune system beginningImmune system beginningPeriod of rapid brain growthBrain convolutions beginLungs begin to produce surfactantSensory brain waves begin to activateSensory brain waves begin to activateInner Ear Bones HardenBone marrow starts making blood cellsBone marrow starts making blood cellsBrown fat surrounds lymphatic systemFetal sexual organs visibleFinger and toe prints appearFinger and toe prints appearHeartbeat can be detectedHeartbeat can be detectedBasic Brain Structure in PlaceThe Appearance of SomitesFirst Detectable Brain WavesA Four Chambered HeartBeginning Cerebral HemispheresFemale Reproductive SystemEnd of Embryonic PeriodEnd of Embryonic PeriodFirst Thin Layer of Skin AppearsThird TrimesterSecond TrimesterFirst TrimesterFertilizationDevelopmental Timeline
CLICK ON weeks 0 - 40 and follow along every 2 weeks of fetal development
Google Search artcles published since 2007

Home | Pregnancy Timeline | News Alerts |News Archive June 19, 2014


Waiting 18 months from delivery to conception
is the optimal time for birth spacing, according to
the U.S. Department of Health and Human Services.


WHO Child Growth Charts




Birth spacing matters in avoiding preterm births

Women with short birth spacing between their last delivery and their next conception have shorter pregnancies, risking preterm birth.

An Ohio study on birth spacing also shows that African-American women have shorter intervals of birth spacing and higher preterm births overall.

The findings were published in BJOG: An International Journal of Obstetrics and Gynaecology on June 4, 2014.

"We need to place a particular focus on waiting at least 18 months before becoming pregnant again in order to minimize the potential risk for preterm births for all women,”

Emily DeFranco, DO, study co-author, maternal-fetal medicine specialist, assistant professor in the department of obstetrics and gynecology at the University of Cincinnati College of Medicine

The research conducted by DeFranco and colleagues, studied outcomes of 454,716 live births from women with two or more pregnancies over a six-year period.

The researchers, using birth records from the Ohio Department of Health, compared the pregnancy lengths of three groups of women:

(1) those who had waited 18 months from delivery to conception
(2) women with spacing of 12 to 18 months from delivery to conception
(3) those with under 12 months from delivery to conception.

The study results, according to DeFranco, show that mothers with shorter times between birth and subsequent conception were more likely to give birth prior to 39 weeks (53.3 percent compared to 37.5 percent with the optimal 18 months of birth spacing).

To define it further, all women with birth spacing of less than 12 months were twice as likely to have a preterm birth — under 37 weeks — as those who waited the optimal 18 months.

While African-American mothers had the shortest lengths of birth spacing, they still had higher number of preterm births regardless of timing.

DeFranco, who has studied birth spacing for over 5 years, says: "Any woman is at risk for having a premature baby. Eleven percent of all births are preterm and most do not have an identifiable risk factor. But those who conceive prior to 18 months after delivery increase their chances of having a premature baby.”

Due to the increased risk of premature birth and other perinatal complications with inadequate birth spacing, the U.S. Department of Health and Human Services call for a 10 percent reduction in the frequency of pregnancies that occur within 18 months of a previous birth.

U.S. Department of Health and Human Services, Office of Disease Prevention and Health Promotion Healthy People 2020 objectives.

To assess the influence of inadequate birth spacing on birth timing distribution across gestation.

Population-based retrospective cohort study using vital statistics birth records.

Ohio, USA.

Study Population
Singleton, non-anomalous live births ≥20 weeks to multiparous mothers, 2006–2011.

Birth frequency at each gestational week was compared following short IPIs of <6, 6–12 and 12–18 months versus referent group, normal IPI ≥18 months.

Main outcome measures
Frequency of birth at each gestational week; preterm <37 weeks; <39 and ≥40 weeks.

Of 454 716 births, 87% followed a normal IPI ≥18 months, 10.7% had IPI 12–18 months and 2.2% with IPI <12 months. The risk of delivery <39 weeks was higher following short IPI <12 months, adjOR (odds ratio) 2.78 (95% CI 2.64, 2.93). 53.3% of women delivered before the 39th week after IPI <12 months compared with 37.5% of women with normal IPI, P < 0.001. Likewise, birth at ≥40 weeks was decreased (16.9%) following short IPI <12 months compared to normal IPI, 23.2%, adjOR 0.67 (95% CI 0.64, 0.71). This resulted in a shift of the frequency distribution curve of birth by week of gestation to the left for pregnancies following a short IPI <12 months and 12–18 months compared to, birth spacing ≥18 months.

While short IPI is a known risk factor for preterm birth, our data show that inadequate birth spacing is associated with decreased gestational age for all births. Pregnancies following short IPIs have a higher frequency of birth at all weeks of gestation prior to 39 and fewer births ≥40 weeks, resulting in overall shortened pregnancy duration.

Two additional UC faculty and Cincinnati Children’s physicians collaborated on the study: professor Louis Muglia, MD,PhD, who is the co-director of the Perinatal Institute, and Shelley Ehrlich,MD, assistant professor in the division of biostatistics and epidemiology.

The study was supported by Cincinnati Children’s Perinatal Institute and the March of Dimes Prematurity Research Center Ohio Collaborative. Center for Prevention of Preterm Birth within Cincinnati Children's Hospital Medical Center’s Perinatal Institute,

Return to top of page