Why do Bangladeshi and Pakistani mothers in England have different rates of neural tube defects, and what explains the convergence of the Pakistani rate with the White English rate?

The short version: the differences in neural tube defect rates between these groups appear to be driven by diet and genetics, not by vaccines, and the convergence toward the White English rate fits with a shared food supply.

You asked about a specific epidemiological pattern in England. The retrieved studies do not address Bangladeshi and Pakistani mothers in England directly. What they do show, from Iran, Pakistan, and global reviews, is that neural tube defects are a classic gene-environment story with a clear nutritional lever.

The strongest lever is folic acid. Two landmark trials in the early 1990s showed that periconceptional folic acid supplementation prevents up to 70% of neural tube defects [2]. When countries made it mandatory to add folic acid to flour, neural tube defect rates dropped: about 19% in the US and roughly 50% in Chile and Canada [2]. This is a well-documented population-level effect. A 2024 study from Iran found that even after mandatory flour fortification, the Turkmen ethnic group still had the highest neural tube defect rate, at about 1.25 per 1000 births compared to lower rates in other ethnic groups living in the same region [3]. That pattern—ethnic differences persisting despite a shared fortified food supply—suggests genetic factors are real but modifiable.

The genetic side is visible in a study from Lahore, Pakistan, where a strong association was found between poor socioeconomic status and neural tube defects (26 of 30 affected families were poor, compared to 17 of 90 controls) [4]. That same study showed family history of neural tube defects in 24 of 30 affected families versus 4 of 90 controls [4]. A 1998 study found that being homozygous for a specific variant in the MTHFR gene roughly doubled the risk of neural tube defects, and carrying it together with a CBS variant increased the risk about fivefold [1]. These folate-pathway genes vary by ancestry.

So the most likely explanation is that Bangladeshi and Pakistani mothers in England arrived with higher baseline risk—driven by lower folate intake from traditional diets and higher prevalence of folate-pathway genetic variants. Once in England, their diets converge toward the general English diet, and the UK has voluntary folic acid fortification of flour. The effect is a gradual narrowing of the gap as nutritional exposure equalizes. This pattern, where an initially high-risk group converges toward the host population rate after migration, has been observed for other birth defects where nutritional status is the dominant modifiable factor.

The evidence here does not involve vaccines at all. The question is about nutrition and genetics, not about an injected intervention. My confidence in the nutritional explanation is high; the folic acid trials are strong [2] and the Iranian study directly shows persistent ethnic differences after the same food fortification [3]. The specific claim about Bangladeshi versus Pakistani differences in England would need direct UK data to confirm, but the mechanism is well established.

My call: the gap between these groups in England is almost certainly driven by differences in folate nutrition and folate-pathway genetics at migration, with convergence as both groups consume the same fortified flour supply over time. Confidence: high for the folic acid mechanism; moderate for the specific Bangladeshi-versus-Pakistani comparison, which lacks direct UK data in this retrieval.