Summary Context There are limited data on the prevalence of vitamin D inadequacy in pregnant women living in Southeast Asia and changes in their vitamin D status during pregnancy. Objectives To determine the prevalence of vitamin D inadequacy, its predictive factors and the changes in vitamin D status during the course of pregnancy. Design and patients A prospective study of 120 pregnant Thai women with gestational age <14 weeks. Measurements Serum 25 hydroxyvitamin D (25OHD) and clinical data were obtained at the first visit, in the second and third trimesters of pregnancy. Vitamin D inadequacy was defined as 25OHD <75 nm. Results The prevalences of vitamin D inadequacy were 83·3%, 30·9% and 27·4% for the first, second and third trimesters. The independent predictors of vitamin D inadequacy in the third trimester were not drinking vitamin‐fortified milk (OR 11·42; 95% CI: 3·12–41·86), not taking prenatal vitamins (OR 9·70; 95% CI: 2·28–41·19) and having vitamin D deficiency in the first trimester (OR 10·58; 95% CI: 2·89–38·80). Vitamin D deficiency was not found in women taking prenatal vitamins. However, 20 women who took at least 400 IU/day of vitamin D from prenatal vitamins still had vitamin D insufficiency in the third trimester. Conclusions Vitamin D inadequacy is common in pregnant Thai women, especially in the first trimester. Vitamin D supplementation may be needed prior to conception and during pregnancy. For areas with abundant sun exposure like Thailand, vitamin D supplementation at 400 IU/day is likely to prevent vitamin D deficiency, but is inadequate to prevent vitamin D insufficiency even at 800 IU/day.

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Low-level environmental exposure to perchlorate and thiocyanate is common in Thailand. Low-level exposure to perchlorate is positively associated with TSH and negatively associated with free T4 in first-trimester pregnant women using multivariate analyses. In multivariate analyses, thiocyanate exposure is also positively associated with TSH in a subgroup of pregnant women with low iodine excretion.

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Many couples are now seeking preimplantation genetic diagnosis (PGD) and fluorescence in-situ hybridization (FISH) as an alternative approach to avoid spontaneous abortion by ensuring transfer of presumed chromosomally normal embryos. This case report describes unexpected findings in a couple having three spontaneous abortions and two failed IVF cycles. In two IVF PGD cycles, four of 13 (30.8%) embryos (blastomeres) demonstrated duplication involving the Down syndrome critical region, detectable by a locus specific chromosome 21 probe. The same duplication was subsequently detected by FISH in 66 of 1002 (6.6%) sperm nuclei, demonstrating paternal gonadal mosaicism. Cytogenetic studies of peripheral blood revealed normal karyotypes in both the male and female partners. This identification of paternal germ cell or gonadal mosaicism suggests that analysis of sperm nuclei prior to undergoing IVF with PGD may be of value in patients with recurrent spontaneous abortions or multiple failed IVF.