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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
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Plastic BPS chemical harms human egg cells

In a new study, UCLA researchers have found that Bisphenol S (BPS) is just as harmful to the reproductive system as bisphenol A (BPA), the chemical it is supposed to replace. In fact, BPS damages a woman's eggs at lower doses than BPA.

Bisphenol S, a chemical used to manufacture polycarbonate water bottles and many other products such as epoxy glues and cash receipts, is an increasingly common replacement for bisphenol A, the of which was discontinued because of concerns about its harmful effects on the reproductive system.

While looking for replacements to toxic chemicals, manufacturers tend to choose substitute chemicals that, while technically different, often share similar physical properties. Due to increasing consumer pressure, companies have replaced BPA with other related compounds now found in many "BPA-free" products. However, uncertainties led the researchers to ask whether BPS could impart detrimental effects on reproduction similar to BPA's. Their results appear in PLOS Genetics.

The researchers exposed a common laboratory model, the roundworm, to several concentrations of BPA and/or BPS that approximate the levels of BPA and/or BPS found in humans. They then followed the worms through the duration of their reproductive periods and measured their fertility.

Researchers observed that compared to the controls, worms exposed to either BPA or BPS, or combination of the two, had decreased fertility. Surprisingly, these effects were seen at lower internal BPS doses than those of BPA suggesting that BPS may be more damaging to the reproductive system. This was especially significant when they examined the viability of young embryos.

These findings are also a cause for concern in humans as the same reproductive processes that are disrupted by BPS in roundworms are found in mammals. Furthermore, as noted above BPS products are already found in a plethora of consumer products.

"This study clearly illustrates the issue with the 'whack-a-mole' approach to chemical replacement in consumer products. There is a great need for the coordinated safety assessment of multiple substitutes and mixtures of chemicals before their use in product replacement. But the good news is that a number of governmental programs and academic labs are now moving in that direction".

Patrick Allard, assistant professor of environmental health sciences at the UCLA Fielding School of Public Health, and the study's senior author.

Concerns about the safety of Bisphenol A, a chemical found in plastics, receipts, food packaging and more, have led to its replacement with substitutes now found in a multitude of consumer products. However, several popular BPA-free alternatives, such as Bisphenol S, share a high degree of structural similarity with BPA, suggesting that these substitutes may disrupt similar developmental and reproductive pathways. We compared the effects of BPA and BPS on germline and reproductive functions using the genetic model system Caenorhabditis elegans. We found that, similarly to BPA, BPS caused severe reproductive defects including germline apoptosis and embryonic lethality. However, meiotic recombination, targeted gene expression, whole transcriptome and ontology analyses as well as ToxCast data mining all indicate that these effects are partly achieved via mechanisms distinct from BPAs. These findings therefore raise new concerns about the safety of BPA alternatives and the risk associated with human exposure to mixtures.

Author Summary
The intricacy of dealing with chemical alternatives is particularly salient in the case of Bisphenol A which was largely driven out of commercial products in North America by consumer and NGO pressure. However, when choosing chemicals with similar physical attributes, substitutes are most often chosen among chemicals with related structural properties. Therefore, it is essential to carefully assess in which ways the substitute differ enough from the original chemical so as not to elicit the same biological responses while conserving the desirable physical characteristics. Here, we show that both BPA and its common substitute BPS elicit a strong negative effect on germline function in a canonical model for the study of germ cell differentiation: the nematode C. elegans. However, by performing and analyzing multiple targeted as well as unbiased gene expression studies, we show that, unexpectedly, these reproductive defects are mainly achieved through independent genetic responses. We further validated these results in mammals by performing an in-depth analysis of curated mammalian toxicity databases (ToxCast, Tox21) containing over 125 in vitro assays for 4 BPA substitutes. Our results highlight the need for coordinated safety assessment of multiple substitutes and mixtures of these chemicals before their use in product replacement.

Authors of the study: Yichang Chen, Le Shu, Zhiqun Qiu, Dong Yeon Lee, Sara Settle, Shane Que Hee, Donatello Telesca, Xia Yang and Patrick Allard, all of UCLA.

Published in the journal PLOS Genetics.

The research was funded by the National Institutes of Health/National Institute of Environmental Health Sciences (R00 NIH/NIEHS R00ES020353); National Institute of Environmental Health Sciences' Training in Molecular Toxicology (T32 NIH/NIEHS ES015457); Center for Alternatives to Animal Testing; and the Burroughs Wellcome Fund's Innovation in Regulatory Science Award.
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Aug 19, 2016   Fetal Timeline   Maternal Timeline   News   News Archive   

Researchers observed that compared to the controls, worms exposed
to either BPA or BPS, or combination of the two, had decreased fertility..
Image Credit: Safer/Chemicals.org



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