Background Lithium is prescribed during pregnancy, but there is limited information about pregnancy and neonatal outcomes following in utero exposure. Thus, this study aimed to investigate the associations between lithium use and adverse pregnancy and neonatal outcomes. Methods This population-based cohort study examined associations between maternal lithium use and major adverse pregnancy and neonatal outcomes via inverse probability weighted propensity score regression models. Results Of 854,017 women included in this study, 434 (0.05%) used lithium during pregnancy. Among pre-specified primary outcomes, lithium use during pregnancy was associated with an increased risk of spontaneous preterm birth (8.7% vs 3.0%; adjusted relative risk [aRR] 2.64 95% CI 1.82, 3.82) and birth of a large for gestational age infant (9.0% vs 3.5%; aRR 2.64 95% CI 1.91, 3.66), but not preeclampsia nor birth of a small for gestational age infant. Among secondary outcomes, lithium use was associated with an increased risk of cardiac malformations (2.1% vs 0.8%; aRR 3.17 95% CI 1.64, 6.13). In an analysis restricted to pregnant women with a diagnosed psychiatric illness (n=9552), associations remained between lithium and spontaneous preterm birth, birth of a large for gestational age infant, and cardiovascular malformations; and a positive association with neonatal hypoglycaemia was also found. These associations were also apparent in a further analysis comparing women who continued lithium treatment during pregnancy to those who discontinued prior to pregnancy. Conclusions Lithium use during pregnancy is associated with an increased risk of spontaneous preterm birth and other adverse neonatal outcomes. These potential risks must be balanced against the important benefit of treatment and should be used to guide shared decision-making.

Aim: To assess the relationship between severity of small for gestational age (SGA) and the risk of poor school performance, and to investigate whether adult stature modifies this risk. Methods: 1,088,980 Swedish children born at term between 1973 and 1988 were categorized into severe SGA (less than –3 standard deviations (SD) of expected birth weight), moderate SGA (–2.01 to –3 SD), mild SGA (–1.01 to –2 SD), and appropriate for gestational age (–1 to 0.99 SD). The risk of poor school performance at the time of graduation from compulsory school (grades <10th percentile) was calculated using unconditional logistic regression models and adjusted for socio-economic factors. In a sub-analysis, we stratified boys by adult stature, and adjusted for maternal but not paternal height. Results: All SGA groups were significantly associated with an increased risk of poor school performance, with adjusted odds ratios and 95% confidence intervals ranging from 1.85 (1.65–2.07) for severe SGA to 1.25 (1.22–1.28) for mild SGA. In the sub-analysis, all birth weight groups were associated with an increased risk of poor school performance among boys with short stature compared to those with non-short stature. Conclusion: Mild SGA is associated with a significantly increased risk of poor school performance, and the risk increases with severity of SGA. Further, this risk diminishes after adequate catch-up growth.

Today we lack knowledge if size at birth and gestational age interact regarding postnatal growth pattern in children born at 32 gestational weeks or later. This population-based cohort study comprised 41,669 children born in gestational weeks 32–40 in Uppsala County, Sweden, between 2000 and 2015. We applied a generalized least squares model including anthropometric measurements at 1.5, 3, 4 and 5 years. We calculated estimated mean height, weight and BMI for children born in week 32 + 0, 35 + 0 or 40 + 0 with birthweight 50 th percentile (standardized appropriate for gestational age, s AGA) or 3 rd percentile (standardized small for gestational age, s SGA). Compared with children born s AGA at gestational week 40 + 0, those born s AGA week 32 + 0 or 35 + 0 had comparable estimated mean height, weight and BMI after 3 years of age. Making the same comparison, those born s SGA week 32 + 0 or 35 + 0 were shorter and lighter with lower estimated mean BMI throughout the whole follow-up period. Our findings suggest that being born SGA and moderate preterm is associated with short stature and low BMI during the first five years of life. The association seemed stronger the shorter gestational age at birth.

Fetal growth restriction is a strong risk factor for perinatal morbidity and mortality. Reliable standards are indispensable, both to assess fetal growth and to evaluate birthweight and early postnatal growth in infants born preterm. The aim of this study was to create updated Swedish reference ranges for estimated fetal weight (EFW) from gestational week 12–42. This prospective longitudinal multicentre study included 583 women without known conditions causing aberrant fetal growth. Each woman was assigned a randomly selected protocol of five ultrasound scans from gestational week 12 + 3 to 41 + 6. Hadlock’s 3rd formula was used to estimate fetal weight. A two-level hierarchical regression model was employed to calculate the expected median and variance, expressed in standard deviations and percentiles, for EFW. EFW was higher for males than females. The reference ranges were compared with the presently used Swedish, and international reference ranges. Our reference ranges had higher EFW than the presently used Swedish reference ranges from gestational week 33, and higher median, 2.5th and 97.5th percentiles from gestational week 24 compared with INTERGROWTH-21st. The new reference ranges can be used both for assessment of intrauterine fetal weight and growth, and early postnatal growth in children born preterm.

Objective To investigate whether polycystic ovary syndrome (PCOS) is associated with increased risk of stillbirth and whether any such association is linked to PCOS with a severe hyperandrogenic profile. Design Nationwide register‐based cohort study. Setting Sweden. Population The cohort consisted of women giving birth to singleton infants in 1997–2015. All women with a diagnosis of PCOS in the period 1997–2017 and a randomly selected reference group of women without PCOS diagnosis were included. PCOS with a severe hyperandrogenic profile was defined as a PCOS diagnosis with at least two dispensations of prescribed anti‐androgens during 2005–2017. Methods The risk of stillbirth in women with PCOS was estimated through multiple logistic regression, using women without PCOS as a reference. Risks were expressed as adjusted odds ratios (aORs) with 95% confidence intervals (95% CIs), adjusted for maternal age, parity, body mass index, type‐1 diabetes, educational level and country of birth. Main outcome measures Stillbirth, at ≥22 weeks of gestation in 2008–2015 and at ≥28 weeks of gestation in 1997–2007. Results Compared with women without PCOS (n = 241 750), women with PCOS (n = 41 851) had a 50% increased risk of stillbirth (aOR 1.50, 95% CI 1.28–1.77). The incidence of stillbirth in women with PCOS was particularly increased at term. Women with PCOS and a severe hyperandrogenic profile (n = 13 713) did not have a stronger association with stillbirth than women with PCOS who did not have such a profile. Conclusions PCOS is associated with stillbirth and should be considered as a possible risk factor in antenatal care. Further research is warranted to investigate possible causal mechanisms. Tweetable abstract Women with PCOS have increased risk of stillbirth, and the incidence is particularly increased at term.