Introduction - During the first lockdown related to the COVID-19 pandemic (March 17–May 11, 2020), the High Council for Public Health (HCSP) warned of the potential impact of this lockdown on children’s lifestyles and on their physical and mental health. The objective of this analysis is to describe the impact of the first lockdown on several health indicators for pregnant women and children and to compare these indicators across populations with different characteristics using data from surveys conducted in the maternal and child health (PMI) service and in municipal daycare centers, or early childhood care facilities (EAPE), by the City of Paris’s Department of Family and Early Childhood (DFPE). Materials and Methods - The PMI survey (EPMI) was conducted via a self-administered questionnaire among the public in October 2020, and the daycare center survey (EEAPE) was conducted online in November 2020. Two questionnaires were developed: one for parents of children (QE) and one for pregnant women or women who had given birth (QF). The data collected are based on parents’ self-reports. Based on the type of housing in which families lived during lockdown, four groups were identified: “in usual individual housing” and “in very low-income housing” for the EPMI; “in usual individual housing” and “in other individual housing” for the EEAPE. The EPMI analysis population includes 500 children (aged 7 months to 2 years) and 956 women; the EEAPE population includes 3,185 children. A descriptive analysis and a comparison of characteristics between populations within the same survey were conducted. Results - Families in the EEAPE survey experienced lockdown under better conditions (more spacious housing, more frequent presence of a spouse) than those in the EPMI survey. At least 20% of parents in the EEAPE and 25% of parents in the EPMI reported a negative impact of the first lockdown on the studied indicators of children’s health. In the EPMI, the frequency of certain negative indicators was higher for families in public housing, such as the onset of sleep disturbances or difficulties in the relationship with the child. Conversely, in the EEAPE, the frequency of some of these indicators was lower for families living outside their usual residence. Among pregnant women, 68.8% reported being “particularly worried” during this period, and health appointments were canceled for 29.5% of them. Conclusion - The first lockdown had an overall negative impact on the health of the public served by PMI and municipal daycare centers in Paris. However, this impact appears to vary depending on the conditions under which the lockdown was experienced.