Aim Breastfeeding has numerous advantages. Our aim was to investigate whether breastfeeding initiation and duration in women with pregnancies conceived through in vitro fertilisation differ from spontaneously conceived pregnancies. Methods This is a comparative cross‐sectional study about breastfeeding behaviour performed at the Bern University Hospital including mothers of singletons conceived by in vitro fertilisation (n = 198) with or without gonadotropin stimulation between 2010 and 2016 (in vitro fertilisation group). They were compared to a population‐based control group (n = 1421) of a randomly selected sample of mothers in Switzerland who delivered in 2014. Results A total of 1619 women were included in this analysis. Breastfeeding initiation rates were high, similar between the in vitro fertilisation group (93.4%) and the control group (94.8%). No increased risk of stopping breastfeeding earlier after in vitro fertilisation treatment compared to the control group could be found over the observational period of 12 months (HR = 1.00, 95% CI 0.83‐1.20, P = .984). There was no difference in breastfeeding initiation or duration after gonadotropin‐stimulated vs unstimulated in vitro fertilisation. Conclusion In Switzerland, in vitro fertilisation treatments were not associated with earlier breastfeeding cessation. This result is reassuring for mothers undergoing in vitro fertilisation.

Study question Is there a difference in growth or weight gain of children conceived after IVF with or without gonadotropin-stimulation compared to standard growth references? Summary answer: We observed no difference in growth between children conceived after IVF with or without gonadotropin-stimulation and spontaneously conceived children. What is known already In recent studies, singletons conceived after IVF cycles had lower birth weight than spontaneously conceived singletons. The etiology of the impaired intrauterine growth is unclear, but insufficiency of placental function or possible epigenetic effects is discussed. Data regarding normalization or continuation of reduced birth weight are controversial. The growth of children born after unstimulated natural cycle IVF (NC-IVF) has never been studied. Study design, size, duration Single-center, university based cohort study. 139 singletons born after NC- IVF and children born after conventional gonadotropin stimulated IVF (cIVF) in 2010 –2017 were studied. Stimulation dosage in cIVF was ≥150 IU/d human gonadotropin. Participants/materials, setting, methods We collected weight, length and head circumference at birth and at one, two, four, six, 12, 18 and 24 months. We calculated standard deviation scores based on national growth references. Growth parameters (weight, length and head circumference) were compared between NC-IVF and cIVF singletons (stimulated with ≥150 IU/d human gonadotropin) using Mann-Whitney U tests. Main results and the role of chance In general, growth of children conceived after IVF did not differ from national references. Of the 139 singletons conceived, 98 singletons were conceived after NC-IVF and 41 after cIVF. The parents did not differ in ethnicity, age, BMI or health status between groups, and there was no significant difference in gestational age, pregnancy complications and smoking or breastfeeding habits either. The median birth weight in NC-IVF children was 3.4kg (0.1 standard deviation score, SDS) and in cIVF 3.3kg (–0.3 SDS) (p = 0.53). Median length at birth in NC-IVF was 50cm (–0.5 SDS) and did not differ from cIVF children 50cm (–0.8 SDS) (p = 0.52). At age 12 months, the median weight was 9.3kg (0.0 SDS) for NC-IVF children compared to 9.0kg (–1.7 SDS) for cIVF children (p = 0.44). Median lengths was 75cm (0.1 SDS) in NC-IVF versus 71cm (–1.6 SDS) in cIVF children (p = 0.89). At age 24 months, median weight in NC-IVF children was 12.3 kg (0.3 SDS) versus 10.5 kg (–1.2 SDS) in cIVF (p = 0.72) and median lengths 87.5cm (0.1 SDS) in NC-IVF versus 87.6 cm (0.1 SDS) in cIVF children. These discrete non-significant differences in weight and length gain compared to standardized growth curves and between the two groups are reassuring. Limitations, reasons for caution Willingness to participate is prone to selection bias. Further studies with larger samples are needed to confirm these findings. Wider implications of the findings: This is the first study investigating weight and length gain in children after unstimulated IVF. Growth is an important proxy for the health of children. These reassuring results are of imminent importance for the children born after IVF and their parents. Trial registration number BASEC (ID 2015–00235)

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