Nickel (Ni) may accumulate in the human body and has biological toxicity and carcinogenicity. Ni has an extensive impact on the health of pregnant women and fetuses during gestation.To evaluate Ni exposure in pregnant women in Kunming, Yunnan Province, China; to describe the distribution of Ni in the maternal-fetal system and placental barrier function; and to investigate the effect of Ni exposure on fetal health in mothers with pregnancy complications.Seventy-two pregnant women were selected using a case-control design. The women were divided into two groups: The control group (no disease; n = 29) and the disease group [gestational diabetes (GDM), hypertensive disorder complicating pregnancy (HDCP), or both; n = 43]. The pregnant women in the disease group were further divided as follows: 14 cases with GDM (GDM group), 13 cases with HDCP (HDCP group) and 16 cases with both GDM and HDCP (disease combination group). Basic information on the pregnant women was collected by questionnaire survey. Maternal blood, placenta blood and cord blood were collected immediately after delivery. The Ni content in paired samples was determined using inductively coupled plasma mass spectrometry.Compared to the control group, age was higher and body mass index was greater in pregnant women in the disease groups (28.14 ± 2.54 vs 28.42 ± 13.89, P < 0.05; 25.90 ± 3.86 vs 31.49 ± 5.30, P < 0.05). The birth weights of newborns in the HDCP group and the control group were significantly different (2.52 ± 0.74 vs 3.18 ± 0.41, P < 0.05). The content of Ni in umbilical cord blood in the entire disease group was higher than that in the control group (0.10 ± 0.16 vs 0.05 ± 0.07, P < 0.05).In the maternal-fetal system of women with pregnancy complications, the barrier effect of the placenta against Ni is weakened, thus affecting healthy growth of the fetus in the uterus.©The Author(s) 2021. Published by Baishideng Publishing Group Inc. All rights reserved.