NLM5008 Chap.10 Environmental Exposures Before and During Pregnancy
Environmental Exposures Before and During Pregnancy
From behaviour to surroundings
Week 9 asks what a mother's and a father's surroundings, before and while she is pregnant, might mean for their child. The exposures it names are polluted air, heat and cold, the built and urban environment, and chemicals that disrupt hormones, together with the ways these combine with everyday habits that parents can change.
It is the last week with a pre-lecture quiz.
Green space and child behaviour
The first reading follows 408 families in a birth cohort in greater Taipei.
Residential greenness was measured from satellite imagery as the normalised difference vegetation index in buffers of 250 to 2,000 metres, in mid-pregnancy and at ages two to four, and mothers rated behaviour on the Child Behavior Checklist, where higher scores mean more problems. Greater prenatal greenness was associated with fewer attention problems at ages two and three, and postnatal greenness only with attention.
The cohort is urban and relatively advantaged, and satellite greenness says nothing about how parks were used.
Paint fumes at home
The second reading used the Danish National Birth Cohort: 19,000 women interviewed around week 30, of whom 45% reported exposure to paint fumes at home. Birth weight and preterm birth did not differ.
Exposure was associated with a lower risk of small for gestational age, but only for short painting periods and for less-used rooms, the opposite of a dose-response pattern, and the authors attribute it to chance or unmeasured confounding, concluding no causal relationship.
Chemicals that persist
From the Week 6 guest lecture, PFAS are manmade chemicals used since the 1940s in products that resist heat, oil, stains and water.
More than 4,700 are known. PFOS and PFOA persist in water for decades, and in the body PFOS has a half-life of 5.4 years and PFOA 3.8 years.
Short-chain PFAS, introduced as replacements, have unclear effects; one study linked short-chain PFAS in cord blood to more internal abdominal fat in newborns.
Parents, fertility and pollution
The Week 3 readings add two rows: each 10 µg/m³ rise in fine particles was associated with 20% higher odds of female infertility, and paternal solvent exposure with higher pooled odds of neural tube defects.
Reading them together keeps the question of who was exposed, and when, at the front.
What this chapter covers
- 01
The Week 9 scope across air, temperature, built environment and disruptors
- 02
Residential greenness and attention problems in Taipei
- 03
Household paint fumes and fetal growth in Denmark
- 04
Interpreting an unexpected protective odds ratio
- 05
PFAS persistence, bioaccumulation and regulation
- 06
Maternal and paternal exposures placed by window
Worked example · free
Deciding whether a surprising result is protective
- 1Interpret the odds ratio and interval.
- 2Apply the dose-response check.
- 2Offer an alternative explanation and conclude.
Key terms
- Endocrine Disruptor
- A chemical that interferes with hormone signalling.
- NDVI
- A satellite index of vegetation from minus one to one, with higher values meaning more green cover.
- Small For Gestational Age
- Birth weight below the tenth percentile for sex and week of gestation.
- PFAS
- Per- and polyfluoroalkyl substances, persistent manmade chemicals used in heat, stain and water-resistant products.
- Bioaccumulation
- The build-up of a substance in the body because it is taken in faster than it is removed.
- Non-Differential Misclassification
- Exposure errors equally likely in all groups, which tend to bias results toward no effect.
Environmental Exposures Before and During Pregnancy FAQ
What did the Taipei greenness study find?
More residential greenness in mid-pregnancy was associated with fewer attention problems at ages two and three on a mother-rated behaviour checklist. Greenness after birth was associated only with attention, not with other behaviour scales.
Did paint fumes in pregnancy harm babies in the Danish study?
No harm was found. Birth weight and preterm birth were unaffected, and the one significant association pointed toward lower risk of being small for gestational age, which the authors attribute to chance or confounding, concluding no causal relationship.
Why are PFAS described as persistent?
Their strong carbon-fluorine bonds resist breakdown, so degradation takes years, decades or longer. PFOS persists in water for more than four decades and has a half-life in people of about five years, so exposure accumulates over time.
Why might painting after the interview bias the Danish result?
Women interviewed around week 30 who painted afterwards would be classed as unexposed. Such errors, equally likely in all groups, tend to pull an association toward no effect, one reason a small true effect could have been missed.
How does Week 9 connect to earlier weeks?
It extends the life-course idea from diet and habits to surroundings, and it adds the father through paternal solvent exposure, echoing the Week 3 argument that both parents' exposures before conception matter.
Assessment move
For each exposure, write who was exposed, in which window, how exposure was measured and the direction of the result. The measurement column is where most of this week's limitations live.
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