Abnormal Development - Fetal Growth Restriction

Embryology - 30 Apr 2024 Expand to Translate
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Introduction

Relative fetal sizes

The term "Fetal Growth Restriction" (FGR) or intrauterine growth restriction (IUGR) are used to describe when the fetus does not reach full growth potential. This is usually determined by clinical sonography calculations of fetal weight, fetal size, or symmetry.

The fetal period (weeks 9 to 37) is about four times the length of the embryonic period and the clinical term may not relate directly to just the "fetal period", that is a time of extensive growth in size and mass as well as ongoing differentiation of organ systems established in the embryonic period. Clinically this period is generally described as the Second Trimester and Third Trimester. Many of the critical measurements of growth are now carried out by ultrasound and measured at birth including the Birth-Weight.

Historic Embryology
1940 Fetus Physiology
Carnegie Fetal: 95 \| 96 \| 142 \| 145 \| 184 \| 211 \| 217 \| 300 \| 362 \| 448 \| 449 \| 538 \| 590 \| 607 \| 625 \| 662 \| 693 \| 847 \| 858 \| 922 \| 928 \| 948 \| 972 \| 1318 \| 1388 \| 1455 \| 1591 \| 1597b \| 1656 \| 1686 \| 2250a \| 2250b \| 3990 \| 5652 \| 6581 \| 7218

Some Recent Findings

Fetus (week 10)

Inflammation in rat pregnancy inhibits spiral artery remodeling leading to fetal growth restriction and features of preeclampsia^[1] "Fetal growth restriction (FGR) and preeclampsia (PE) are often associated with abnormal maternal inflammation, deficient spiral artery (SA) remodeling, and altered uteroplacental perfusion. Here, we provide evidence of a novel mechanistic link between abnormal maternal inflammation and the development of FGR with features of PE. Using a model in which pregnant rats are administered low-dose lipopolysaccharide (LPS) on gestational days 13.5-16.5, we show that abnormal inflammation resulted in FGR mediated by tumor necrosis factor-α (TNF). Inflammation was also associated with deficient trophoblast invasion and SA remodeling, as well as with altered uteroplacental hemodynamics and placental nitrosative stress. Moreover, inflammation increased maternal mean arterial pressure (MAP) and was associated with renal structural alterations and proteinuria characteristic of PE. Finally, transdermal administration of the nitric oxide (NO) mimetic glyceryl trinitrate prevented altered uteroplacental perfusion, LPS-induced inflammation, placental nitrosative stress, renal structural and functional alterations, increase in MAP, and FGR. These findings demonstrate that maternal inflammation can lead to severe pregnancy complications via a mechanism that involves increased maternal levels of TNF. Our study provides a rationale for the use of antiinflammatory agents or NO-mimetics in the treatment and/or prevention of inflammation-associated pregnancy complications."
A randomised controlled trial comparing standard or intensive management of reduced fetal movements after 36 weeks gestation-a feasibility study^[2] "Women presenting with reduced fetal movements (RFM) in the third trimester are at increased risk of stillbirth or fetal growth restriction. These outcomes after RFM are related to smaller fetal size on ultrasound scan, oligohydramnios and lower human placental lactogen (hPL) in maternal serum. We performed this study to address whether a randomised controlled trial (RCT) of the management of RFM was feasible with regard to: i) maternal recruitment and retention ii) patient acceptability, iii) adherence to protocol. Additionally, we aimed to confirm the prevalence of poor perinatal outcomes defined as: stillbirth, birthweight <10th centile, umbilical arterial pH <7.1 or unexpected admission to the neonatal intensive care unit. ...An RCT of management of RFM is feasible with a low rate of attrition. Investigations decrease maternal anxiety. Participants in the intensive group were more likely to have IOL for RFM. Further work is required to determine the likely level of intervention in the standard care arm in multiple centres, to develop additional placental biomarkers and to confirm that the composite outcome is valid.Trial registration ISRCTN07944306."

More recent papers
This table allows an automated computer search of the external PubMed database using the listed "Search term" text link. This search now requires a manual link as the original PubMed extension has been disabled. The displayed list of references do not reflect any editorial selection of material based on content or relevance. References also appear on this list based upon the date of the actual page viewing. References listed on the rest of the content page and the associated discussion page (listed under the publication year sub-headings) do include some editorial selection based upon both relevance and availability. More? References \| Discussion Page \| Journal Searches \| 2019 References \| 2020 References Search term: Fetal Growth Restriction <pubmed limit=5>Fetal Growth Restriction</pubmed>

Reading

Human Embryology (3rd ed.) Larson Chapter 15: Fetal development and the Fetus as Patient p481-499
The Developing Human: Clinically Oriented Embryology (8th ed.) Moore and Persaud Chapter 6: The Fetal Period: Ninth Week to Birth
Color Atlas of Clinical Embryology (2nd ed.) Moore, Persaud and Shiota Chapter 3: 9th to 38th weeks of human development p50-68

‎‎Fetal Development

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Fetal length and weight change

Second Trimester

Fetus - second trimester
(ultrasound)

Second Trimester
Week 12 - CRL 85 mm, femur length 15 mm, biparietal diameter 25 mm.

Begin by working through the features present in the early 10 week female fetus. Then look in detail at the head development in a 12 week fetus.

**10 Week Fetus** *head images*

Then look in detail at the head development in a 12 week fetus showing both forms of ossification in the skull.

**12 Week Fetus** *head images*

Fetal Head Growth

Second and third trimesters
Second trimester

Third Trimester

Fetus - third trimester
(historic image)

Third trimester Crown-Rump Length

Vibration acoustically of maternal abdominal wall induces startle respone in fetus.
Month 7 - respiratory bronchioles proliferate and end in alveolar ducts and sacs.
Week 37 to 38 Birth.

Links: Third Trimester