An estimated 75,000 people have taken part in a Paris demonstration against government plans to legalise fertility treatment for single women and lesbians.
Waving red and green flags, the crowd marched from the French Senate toward the nearby Tour Montparnasse skyscraper, chanting "Liberty, Equality, Paternity" -- a play on the French republican motto which ends with "Fraternity".
The crowd was estimated at 74,500 by an independent agency which specialises in counting large protest groups. The organisers had been hoping for a turn-out of around 100,000.
"For two years now our attempts at dialogue have gone nowhere... the street is the only place left for us to be heard," Ludovine de la Rochere, president of the Protest for Everyone association, told journalists on Sunday.
President Emmanuel Macron pledged during his 2017 election campaign to push the law despite deep resistance from rightwing opponents as well as conservative Roman Catholics and other religious groups.
They mobilised massively in 2012 and 2013 against a move by Macron's Socialist predecessor François Hollande to legalise marriage for homosexual couples, with one Paris protest attracting 340,000 people according to police.
But that law did not allow lesbian couples or single women to have children via in-vitro fertilisation or other medically assisted means.
Many women have instead been forced to go abroad for such treatments, and French courts often refuse to recognise the second mother's maternity rights in the case of same-sex couples.
Under the proposed law, France's healthcare system would cover the cost of the procedure for all women under 43.
It would also allow children conceived with donated sperm to find out the donor's identity when they turn 18, a change from the country's strict donor anonymity rules.
Opponents say the law deprives children of a necessary paternal figure, threatens the traditional family structure, and would open the door to legalising surrogacy, including for gay men.