Pregnancy

Human childbirth is regarded as uniquely difficult among primates, due to a tight cephalopelvic fit thought to result from an evolutionary trade-off between adaptations to bipedal locomotion and increasing brain size. This impression, however, may be an artefact of past adoption of anthropocentric measurements that underestimate birth challenges in non-human primates. Here we re-evaluate cephalopelvic proportions using species-specific three-dimensional data of the pelvic inlet along with neonatal cranial dimensions from a broad sample of extant primates. Results reveal that maternal body size is a key factor to consider. A tight cephalopelvic fit occurs in species with proportionately larger neonates, smaller pelves or a combination of both. The latter is the case in humans, producing the tightest fit among extant apes, but a similar combination of factors explains much more extreme cephalopelvic proportions in other species. Our findings reveal a diversity of obstetrical dilemmas across primates.

ImportanceGestational environmental chemical exposures are widespread. Some chemicals are known to adversely affect birth outcomes, but many remain understudied.ObjectiveTo evaluate associations of gestational exposure to a priori identified chemicals in 10 classes with birth outcomes in a large, diverse US cohort.Design, setting, and participantsIn the prospective Environmental influences on Child Health Outcomes Cohort study, 5318 mother-child pairs were enrolled from January 1, 2000, to December 31, 2021, with data on gestational urinary chemical concentrations, gestational age at birth, and birth weight. Statistical analysis was performed from January 2024 to February 2026.ExposuresIn single, midgestation (median, 25 weeks [IQR, 21-30 weeks]) urine samples, concentrations of 113 analytes (chemicals or their metabolites) from 10 chemical classes were simultaneously measured: fungicides and herbicides (n = 11), insecticides (n = 20), halogenated phenols (n = 5), organophosphate esters (n = 10), benzophenones (n = 6), bisphenols (n = 14), parabens (n = 6), antimicrobials (n = 2), phthalates or alternative plasticizers (n = 32), and polycyclic aromatic hydrocarbons (PAHs) (n = 7).Main outcomes and measuresLinear mixed-effects regression models with a random effect for site were used to estimate covariate-adjusted differences in gestational age at birth (days) and birth weight-for-gestational age (BW-GA) z scores per IQR increase in urinary analyte concentrations. In secondary analyses, odds ratios (ORs) for preterm birth and small for gestational age (SGA) were estimated.ResultsIn the sample of 5318 mother-child pairs, most infants (2667 female [50%]; median gestational age at birth, 39.0 weeks [IQR, 38.0-40.0 weeks]) were born to college-educated (67% [3218 of 4785]), parous (56% [2815 of 5007]) mothers (median age at delivery, 30.7 years [IQR, 26.1-34.3 years]). A total of 43 of 113 analytes (38%) were detected in 50% or more of samples. Multiple phthalates or alternative plasticizers were associated with younger gestational age at birth or lower BW-GA z scores; for example, summed diisononyl phthalate metabolites were associated with a 0.6-day (95% CI, -1.0 to -0.1 days) younger gestational age (preterm birth OR, 1.16 [95% CI, 1.01-1.34]), and summed phthalate or alternative plasticizers were associated with a 0.06 (95% CI, -0.11 to -0.02) lower BW-GA z score (SGA OR, 1.09 [95% CI, 0.93-1.27]). Two halogenated phenols, benzophenone 8, bisphenol F, and several PAHs were associated with lower BW-GA z scores; for example, 1- and 9-hydroxphenanthrene were associated with a 0.04 (95% CI, -0.08 to -0.01) lower BW-GA z score (SGA OR, 1.13 [95% CI, 1.01-1.27]).Conclusions and relevanceThis large cohort study of diverse US pregnancies found widespread exposure to 10 classes of environmental chemicals, many of which were associated with differences in gestational age at birth or lower BW-GA z scores. These findings indicate that reducing gestational exposure to chemicals, particularly phthalates or alternative plasticizers and PAHs, could promote healthy deliveries and better child outcomes.

AimsGestational diabetes mellitus (GDM) is one of the most common metabolic disorders during pregnancy and is associated with an increased risk of multiple adverse pregnancy outcomes (APOs). Gestational weight gain (GWG) is an important indicator for disease monitoring and intervention; however, evidence regarding the associations between trimester-specific GWG patterns stratified by pre-pregnancy body mass index (BMI) and APOs among Chinese women with GDM remains limited.Materials and methodsRetrospective cohort study of 8, 562 singleton GDM pregnancies delivered at Maternal and Child Health Hospital of Guangxi Zhuang Autonomous Region (Feb 2021-Sep 2025). Women were classified into underweight, normal-weight, overweight, and obesity groups by pre-pregnancy BMI. GWG in early pregnancy, before Oral Glucose Tolerance Test (OGTT), and after OGTT was categorized as inadequate, adequate, or excessive per National Health Commission guidelines for GDM. Multivariable logistic regression with Benjamini-Hochberg false discovery rate (FDR) correction and generalized additive models (GAM) were used to assess associations and nonlinear relationships with APOs.ResultsThe associations between GWG and APOs differed significantly across pre-pregnancy BMI categories. Specifically, excessive GWG before OGTT diagnosis was associated with an increased risk of LGA among normal-weight and overweight women (aOR 1.71, 95% CI 1.38-2.13; and aOR 1.72, 95% CI 1.26-2.37, respectively). Excessive GWG after OGTT diagnosis was associated with an increased risk of preeclampsia (aOR 4.06, 95% CI 2.69-6.12; and aOR 2.49, 95% CI 1.46-4.24, respectively). In addition, excessive GWG before OGTT diagnosis was associated with a lower risk of SGA (aOR 0.39, 95% CI 0.25-0.62) in women with underweight. In women with obesity, no significant associations were observed between GWG and APOs, although the directional trends were generally consistent with those in the overweight group. GAM analyses further supported nonlinear associations between GWG and several APOs.ConclusionStage-specific GWG patterns in GDM pregnancies showed heterogeneous associations with APOs across pre-pregnancy BMI categories. These findings suggest that weight management strategies tailored to both pre-pregnancy BMI and gestational stage may help optimize pregnancy outcomes in women with GDM.