: Fat-soluble 25-hydroxyvitamin D (25-OHD) may be endogenously synthesized or obtained from dietary sources. Notably, it is crucial in calcium homeostasis, gene regulation, and immune system modulation, being even more relevant during prenatal stages, as the embryo utilizes vitamin D obtained from maternal plasma. Moreover, 25-OHD has been recently demonstrated to affect hematological parameters. We aimed to determine the correlation between maternal plasma 25-OHD levels, other blood parameters, and fetal anthropometric outcomes. : Pregnant women attending an obstetrics and gynecology clinic during their gestation period were recruited, and data during follow-ups until the birth of their child were collected (IRB Approval Code: 07-XD-096). Data from 103 pregnant women were analyzed. : Compared to participants with normal levels, pregnant women with inadequate plasma 25-OHD levels exhibited a higher red blood cell count (4.3 ± 0.51 vs. 4.1 ± 0.42; = 0.012) and lower mean corpuscular volume (86.4 ± 8.47 vs. 90.4 ± 6.74; = 0.003), mean corpuscular hemoglobin (28.1 ± 3.34 vs. 29.6 ± 2.70; = 0.008), plasma folate (12.6 ± 5.91 vs. 15.6 ± 5.86; = 0.006), and vitamin B12 (289 ± 174 vs. 352 ± 147; = 0.001) levels. Fish consumption frequency was positively associated with plasma 25-OHD levels. : 25-OHD deficiency was correlated with alterations in hematological markers, plasma folate, and vitamin B12 levels. Given the high prevalence of 25-OHD deficiency in women of fertile age, government policies and healthcare professionals should emphasize vitamin D consumption adequacy in fertile women and expectant mothers.