Fetal growth is associated with long-term health yet no appropriate standards exist for the early identification of undergrown or overgrown fetuses. We sought to develop contemporary fetal growth standards for 4 self-identified US racial/ethnic groups. We recruited for prospective follow-up 2334 healthy women with low-risk, singleton pregnancies from 12 community and perinatal centers from July 2009 through January 2013. The cohort comprised: 614 (26%) non-Hispanic whites, 611 (26%) non-Hispanic blacks, 649 (28%) Hispanics, and 460 (20%) Asians. Women were screened at 8w0d to 13w6d for maternal health status associated with presumably normal fetal growth (aged 18-40 years; body mass index 19.0-29.9 kg/m(2); healthy lifestyles and living conditions; low-risk medical and obstetrical history); 92% of recruited women completed the protocol. Women were randomized among 4 ultrasonography schedules for longitudinal fetal measurement using the Voluson E8 (GE Healthcare, Milwaukee, WI). In-person interviews and anthropometric assessments were conducted at each visit; medical records were abstracted. The fetuses of 1737 (74%) women continued to be low risk (uncomplicated pregnancy, absent anomalies) at birth, and their measurements were included in the standards. Racial/ethnic-specific fetal growth curves were estimated using linear mixed models with cubic splines. Estimated fetal weight (EFW) and biometric parameter percentiles (5th, 50th, 95th) were determined for each gestational week and comparisons made by race/ethnicity, with and without adjustment for maternal and sociodemographic factors. EFW differed significantly by race/ethnicity >20 weeks. Specifically at 39 weeks, the 5th, 50th, and 95th percentiles were 2790, 3505, and 4402 g for white; 2633, 3336, and 4226 g for Hispanic; 2621, 3270, and 4078 g for Asian; and 2622, 3260, and 4053 g for black women (adjusted global P < .001). For individual parameters, racial/ethnic differences by order of detection were: humerus and femur lengths (10 weeks), abdominal circumference (16 weeks), head circumference (21 weeks), and biparietal diameter (27 weeks). The study-derived standard based solely on the white group erroneously classifies as much as 15% of non-white fetuses as growth restricted (EFW <5th percentile). Significant differences in fetal growth were found among the 4 groups. Racial/ethnic-specific standards improve the precision in evaluating fetal growth.

Context: Thyroid diseases are inconsistently reported to increase risk for pregnancy complications. Objective: The objective of this study was to study pregnancy complications associated with common and uncommon thyroid diseases. Design, Setting, and Participants: We analyzed singleton pregnancies (N = 223 512) from a retrospective US cohort, the Consortium on Safe Labor (2002–2008). Thyroid diseases and outcomes were derived from electronic medical records. Multivariable logistic regression with generalized estimating equations estimated adjusted odds ratios (ORs) with 99% confidence intervals (99% CI). Main Outcome Measures: Hypertensive diseases, diabetes, preterm birth, cesarean sections, inductions, and intensive care unit (ICU) admissions were analyzed. Results: Primary hypothyroidism was associated with increased odds of preeclampsia (OR = 1.47, 99% CI = 1.20–1.81), superimposed preeclampsia (OR = 2.25, 99% CI = 1.53–3.29), gestational diabetes (OR = 1.57, 99% CI = 1.33–1.86), preterm birth (OR = 1.34, 99% CI = 1.17–1.53), induction (OR = 1.15, 99% CI = 1.04–1.28), cesarean section (prelabor, OR = 1.31, 99% CI = 1.11–1.54; after spontaneous labor OR = 1.38, 99% CI = 1.14–1.66), and ICU admission (OR = 2.08, 99% CI = 1.04–4.15). Iatrogenic hypothyroidism was associated with increased odds of placental abruption (OR = 2.89, 99% CI = 1.14–7.36), breech presentation (OR = 2.09, 99% CI = 1.07–4.07), and cesarean section after spontaneous labor (OR = 2.05, 99% CI = 1.01–4.16). Hyperthyroidism was associated with increased odds of preeclampsia (OR = 1.78, 99% CI = 1.08–2.94), superimposed preeclampsia (OR = 3.64, 99% CI = 1.82–7.29), preterm birth (OR = 1.81, 99% CI = 1.32–2.49), induction (OR = 1.40, 99% CI = 1.06–1.86), and ICU admission (OR = 3.70, 99% CI = 1.16–11.80). Conclusions: Thyroid diseases were associated with obstetrical, labor, and delivery complications. Although we lacked information on treatment during pregnancy, these nationwide data suggest either that there is a need for better thyroid disease management during pregnancy or that there may be an intrinsic aspect of thyroid disease that causes poor pregnancy outcomes.

Optimal fetal growth is a foundation for long-term health, whereas abnormal growth affects disease risk across the lifespan. Both fetal growth restriction and overgrowth are associated with increased fetal, infant and child mortality and morbidity, ^{1, 2} as well as being factors in reproductive disorders and later-onset diseases. Population-level data suggest a relationship between diminished birth size and chronic disorders, including hypertension, ^{3, 4} supporting the early origins of health and disease research paradigm. ⁵

Systematic evaluation and estimation of growth trajectories in twins require ultrasound measurements across gestation that are performed in controlled clinical settings. Currently, there are few such data for contemporary populations. There is also controversy about whether twin fetal growth should be evaluated with the use of the same benchmarks as singleton growth. Our objective was to define the trajectory of fetal growth in dichorionic twins empirically using longitudinal 2-dimensional ultrasonography and to compare the fetal growth trajectories for dichorionic twins with those based on a growth standard that was developed by our group for singletons. A prospective cohort of 171 women with twin gestations was recruited from 8 US sites from 2012-2013. After an initial sonogram at 11 weeks 0 days-13 weeks 6 days of gestation during which dichorionicity was confirmed, women were assigned randomly to 1 of 2 serial ultrasonography schedules. Growth curves and percentiles were estimated with the use of linear mixed models with cubic splines. Percentiles were compared statistically at each gestational week between the twins and 1731 singletons, after adjustment for maternal age, race/ethnicity, height, weight, parity, employment, marital status, insurance, income, education, and infant sex. Linear mixed models were used to test for overall differences between the twin and singleton trajectories with the use of likelihood ratio tests of interaction terms between spline mean structure terms and twin-singleton indicator variables. Singleton standards were weighted to correspond to the distribution of maternal race in twins. For those ultrasound measurements in which there were significant global tests for differences between twins and singletons, we tested for week-specific differences using Wald tests that were computed at each gestational age. In a separate analysis, we evaluated the degree of reclassification in small for gestational age, which was defined as <10th percentile that would be introduced if fetal growth estimation for twins was based on an unweighted singleton standard. Women underwent a median of 5 ultrasound scans. The 50th percentile abdominal circumference and estimated fetal weight trajectories of twin fetuses diverged significantly beginning at 32 weeks of gestation; biparietal diameter in twins was smaller from 34-36 weeks of gestation. There were no differences in head circumference or femur length. The mean head circumference/abdominal circumference ratio was progressively larger for twins compared with singletons beginning at 33 weeks of gestation, which indicated a comparatively asymmetric growth pattern. At 35 weeks of gestation, the average gestational age at delivery for twins, the estimated fetal weights for the 10th, 50th, and 90th percentiles were 1960, 2376, and 2879 g for dichorionic twins, respectively, and 2180, 2567, and 3022 g for the singletons, respectively. At 32 weeks of gestation, the initial week when the mean estimated fetal weight for twins was smaller than that of singletons, 34% of twins would be classified as small for gestational age with the use of a singleton, non-Hispanic white standard. By 35 weeks of gestation, 38% of twins would be classified as small for gestational age. The comparatively asymmetric growth pattern in twin gestations, initially evident at 32 weeks of gestation, is consistent with the concept that the intrauterine environment becomes constrained in its ability to sustain growth in twin fetuses. Near term, nearly 40% of twins would be classified as small for gestational age based on a singleton growth standard.