A Qatar birth cohort found tripled stillbirth odds in consanguineous pregnancies

A retrospective cohort study drawing on Qatar's maternity registry found that pregnancies within consanguineous unions carried roughly three times the odds of stillbirth and of neonatal death compared with non-consanguineous pregnancies — and that the excess neonatal mortality persisted among babies with no detectable structural anomaly [s1].

The scale of the exposure

Consanguineous marriage — union between people who share a recent common ancestor — is common across the Middle East, and Qatar's rate is high even by regional standards. In this cohort, covering pregnancies of at least 20 weeks' gestation, 30.8% of women were in consanguineous unions; among Qatari women specifically the figure was 46.4% [s1]. Of the consanguineous unions, 74% were first-degree [s1] — the closest category the study distinguished, and the one where the shared proportion of the genome is highest.

That is a very different exposure prevalence from the populations most perinatal epidemiology is built on, which is precisely why the authors argue large population-based data from the region has been missing [s1].

What the study measured

Women were classified by their relationship to their spouse, with consanguineous unions further split into first-degree and second-degree [s1]. Outcomes tracked were congenital anomalies, chromosomal anomalies, preterm birth, stillbirth, neonatal death, and small-for-gestational-age birth [s1].

Raw incidences in consanguineous unions were 21 anomalies, 4.3 stillbirths, and 2.4 neonatal deaths per 1,000 births [s1]. After adjustment for confounders, consanguineous unions had higher odds of major congenital anomalies (adjusted odds ratio 1.37, p = 0.049), stillbirth (aOR 3.10, p = 0.007), and — in babies without anomalies — neonatal death (aOR 3.15, p = 0.042) [s1].

Why the non-anomalous finding is the interesting one

The conventional explanation for consanguinity's perinatal effects runs through autosomal recessive disease: closely related parents are more likely to carry the same recessive variant, the child inherits two copies, and the resulting disorder or malformation causes the loss. On that account, the excess deaths should cluster in babies with identifiable anomalies.

This cohort found elevated neonatal death odds specifically in non-anomalous babies [s1] — infants who were, morphologically, normal. The authors state the association plainly and do not claim a mechanism for it. Possible explanations are not distinguished by these data: recessive metabolic or functional disorders that leave no structural signature, placental factors, or residual confounding by something correlated with consanguinity that the adjustment did not capture.

The p-values on two of the three headline results — 0.049 for anomalies and 0.042 for non-anomalous neonatal death — sit just under the conventional 0.05 threshold [s1]. That is worth noting rather than glossing: results that close to the line are the ones most sensitive to modelling choices and least reliable as point estimates. The stillbirth result at p = 0.007 is the more robust of the three.

Who was in consanguineous unions

The study also reports the social gradient. Younger maternal age, obesity, higher parity, and lower maternal education were all associated with consanguineous unions [s1]. Each of those is independently associated with adverse perinatal outcomes in the wider literature, which is the reason the analysis adjusts for confounders — and also the reason residual confounding remains a live concern in any observational study of this kind.

The expatriate finding

The cohort included both Qatari and non-Qatari women, and the study separated them. The adjusted differences were larger in non-Qatari women than in Qatari women [s1]. The anomaly pattern differed too: cardiovascular anomalies were the most common overall and were higher in first-degree consanguineous unions, while nervous-system anomalies were higher among expatriates [s1].

The study does not explain why the effect would be larger in the expatriate population. Access to preconception genetic services, differences in which national or ethnic groups are represented among expatriate consanguineous couples, and differences in the underlying carrier frequencies of specific recessive variants are all plausible and none is tested here.

What this does and does not support

This is a single-country retrospective registry cohort. It establishes association, not causation, and its findings are anchored to Qatar's specific population structure. Consanguinity rates, the mix of first- versus second-degree unions, and the local landscape of recessive variants all differ between countries, so the effect sizes here should not be read as a universal multiplier.

What the study does contribute is scale in a setting where scale was lacking, and a finding — excess neonatal death without structural anomaly — that does not fit neatly inside the standard explanation. The authors frame the intent as raising awareness of the consequences of consanguineous unions in Qatar [s1]; nothing in the paper constitutes guidance for any individual couple, and reproductive decisions of this kind sit with families and their own clinicians.

What to watch next

Whether genomic follow-up can identify what is killing the non-anomalous infants. Qatar has a large national biobank with whole-genome sequencing already in place, and linking perinatal registry outcomes to that sequencing is the obvious way to test whether unidentified recessive disorders account for the gap — or whether something other than recessive genetics is doing the work.

Sources

1. Consanguinity and adverse fetal outcomes — a population-based cohort study from a multiethnic population in the Middle East — BMC Pregnancy and Childbirth, 17 December 2025 (primary)